Chemistry Quiz: Interpret Coefficients As Mole Ratios
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Interpret Coefficients As Mole RatiosQuestion 1 of 20

Ammonia can be made by the balanced equation N2+3H2→2NH3\mathrm{N_2 + 3H_2 \rightarrow 2NH_3} According to the coefficients, how many moles of H2\mathrm{H_2} react with 11 mol of N2\mathrm{N_2}?

11 mol
22 mol
33 mol
66 mol
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Chemistry Quiz

Chemistry Quiz: Interpret Coefficients As Mole Ratios

Practice Interpret Coefficients As Mole Ratios in Chemistry with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

What this quiz covers

This quiz focuses on Interpret Coefficients As Mole Ratios, giving you a quick way to practice the rules, question types, and explanations that matter most for Chemistry.

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Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

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Question 1

Ammonia can be made by the balanced equation N2+3H2→2NH3\mathrm{N_2 + 3H_2 \rightarrow 2NH_3} According to the coefficients, how many moles of H2\mathrm{H_2} react with 11 mol of N2\mathrm{N_2}?

  1. 11 mol
  2. 22 mol
  3. 33 mol (correct answer)
  4. 66 mol
Explanation: This question tests your understanding that coefficients in balanced chemical equations represent mole ratios—the proportional relationships between amounts of reactants consumed and products formed in a chemical reaction. The coefficients in a balanced equation (the numbers in front of chemical formulas) tell you the ratio of MOLES of each substance involved in the reaction: in 2H2+O2→2H2O2\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O}, the coefficients 2, 1, and 2 mean that 2 moles of hydrogen gas react with 1 mole of oxygen gas to produce 2 moles of water. This ratio is the fundamental relationship—it means for every 1 mole of O2 consumed, exactly 2 moles of H2 are consumed and exactly 2 moles of H2O are produced. The ratio stays constant no matter how much you scale it: 4 moles H2 with 2 moles O2 makes 4 moles H2O (doubled), or 1 mole H2 with 0.5 moles O2 makes 1 mole H2O (halved)—the 2:1:2 ratio is preserved! In the given equation N2+3H2→2NH3\mathrm{N_2 + 3H_2 \rightarrow 2NH_3}, the coefficient of H2 is 3 and N2 is 1 (implied), so for 1 mole of N2, 3 moles of H2 are required, directly from the 1:3 ratio of N2 to H2. Choice C correctly interprets the coefficients as the mole ratio between the specified substances. Choice A might result if you misread the coefficient of H2 as 1, but remember to always check the numbers explicitly written or implied! Reading mole ratios from balanced equations: (1) Locate the two substances you're comparing in the equation. (2) Read their coefficients (the numbers in front—if no number is written, the coefficient is 1). (3) Write the ratio: [coefficient of first substance] : [coefficient of second substance]. Example: from N2+3H2→2NH3\mathrm{N_2 + 3H_2 \rightarrow 2NH_3}, the ratio of N2 to H2 is 1:3 (read coefficients 1 and 3). The ratio of H2 to NH3 is 3:2 (coefficients 3 and 2). The ratio of N2 to NH3 is 1:2 (coefficients 1 and 2). You can find the ratio between ANY two substances in the equation by reading their coefficients! Using mole ratios as conversion factors: mole ratios let you predict amounts! If you know how many moles of one substance you have, you can calculate moles of another using the ratio. From 2H2+O2→2H2O2\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O}, if you have 5 moles of H2, how many moles H2O can form? Ratio H2:H2O is 2:2 or 1:1, so 5 moles H2 produces 5 moles H2O. If you have 5 moles H2, how many moles O2 needed? Ratio H2:O2 is 2:1, so 5 moles H2 needs 2.5 moles O2. The coefficients are your conversion tool—they're not just decorative numbers, they're the mathematical relationship between substances in the reaction!

Question 2

Propane combusts according to the balanced equation C3H8+5O2→3CO2+4H2O\mathrm{C_3H_8 + 5O_2 \rightarrow 3CO_2 + 4H_2O}. What is the mole ratio of CO2\mathrm{CO_2} produced to C3H8\mathrm{C_3H_8} consumed?

  1. 1:31:3
  2. 3:13:1 (correct answer)
  3. 3:83:8
  4. 5:15:1
Explanation: This question tests your understanding that coefficients in balanced chemical equations represent mole ratios—the proportional relationships between amounts of reactants consumed and products formed in a chemical reaction. The coefficients in a balanced equation (the numbers in front of chemical formulas) tell you the ratio of MOLES of each substance involved in the reaction: in 2H2+O2→2H2O2\mathrm{H_2} + \mathrm{O_2} \rightarrow 2\mathrm{H_2O}, the coefficients 2, 1, and 2 mean that 2 moles of hydrogen gas react with 1 mole of oxygen gas to produce 2 moles of water. This ratio is the fundamental relationship—it means for every 1 mole of O2\mathrm{O_2} consumed, exactly 2 moles of H2\mathrm{H_2} are consumed and exactly 2 moles of H2O\mathrm{H_2O} are produced. The ratio stays constant no matter how much you scale it: 4 moles H2\mathrm{H_2} with 2 moles O2\mathrm{O_2} makes 4 moles H2O\mathrm{H_2O} (doubled), or 1 mole H2\mathrm{H_2} with 0.5 moles O2\mathrm{O_2} makes 1 mole H2O\mathrm{H_2O} (halved)—the 2:1:22:1:2 ratio is preserved! In the given equation C3H8+5O2→3CO2+4H2O\mathrm{C_3H_8} + 5\mathrm{O_2} \rightarrow 3\mathrm{CO_2} + 4\mathrm{H_2O}, the coefficient for CO2\mathrm{CO_2} is 3 and for C3H8\mathrm{C_3H_8} is 1 (implied), so the mole ratio of CO2\mathrm{CO_2} produced to C3H8\mathrm{C_3H_8} consumed is 3:13:1, meaning 3 moles of CO2\mathrm{CO_2} from 1 mole of C3H8\mathrm{C_3H_8}. Choice B correctly interprets the coefficients as the mole ratio between the specified substances. A distractor like choice C might pull in unrelated coefficients like 3:83:8 from subscripts, but ratios are from coefficients only, not subscripts or other numbers. Reading mole ratios from balanced equations: (1) Locate the two substances you're comparing in the equation. (2) Read their coefficients (the numbers in front—if no number is written, the coefficient is 1). (3) Write the ratio: [coefficient of first substance] : [coefficient of second substance]. Using mole ratios as conversion factors: mole ratios let you predict amounts! If you know how many moles of one substance you have, you can calculate moles of another using the ratio—they're not just decorative numbers, they're the mathematical relationship between substances in the reaction!

Question 3

In the balanced equation 4Fe+3O2→2Fe2O3\mathrm{4Fe + 3O_2 \rightarrow 2Fe_2O_3} what is the mole ratio of oxygen gas (O2\mathrm{O_2}) to iron(III) oxide (Fe2O3\mathrm{Fe_2O_3})?

  1. 3:23:2 (correct answer)
  2. 2:32:3
  3. 3:43:4
  4. 6:26:2
Explanation: This question tests your understanding that coefficients in balanced chemical equations represent mole ratios—the proportional relationships between amounts of reactants consumed and products formed in a chemical reaction. The coefficients in a balanced equation (the numbers in front of chemical formulas) tell you the ratio of MOLES of each substance involved in the reaction: in 4Fe + 3O₂ → 2Fe₂O₃, the coefficients 4, 3, and 2 mean that 4 moles of iron react with 3 moles of oxygen gas to produce 2 moles of iron(III) oxide. From the equation 4Fe + 3O₂ → 2Fe₂O₃, to find the ratio of oxygen gas (O₂) to iron(III) oxide (Fe₂O₃), I locate O₂ with coefficient 3 and Fe₂O₃ with coefficient 2, giving the ratio 3:2. Choice A correctly identifies this 3:2 ratio, meaning for every 3 moles of O₂ consumed, 2 moles of Fe₂O₃ are produced. The other choices incorrectly reverse the ratio (2:3), propose a different ratio (3:4), or fail to simplify (6:2 should be reduced to 3:1, which is still incorrect). Reading mole ratios from balanced equations: (1) Locate the two substances you're comparing in the equation. (2) Read their coefficients (the numbers in front—if no number is written, the coefficient is 1). (3) Write the ratio: [coefficient of first substance] : [coefficient of second substance]. The 3:2 ratio enables calculations: if 6 moles of O₂ react completely, they produce 4 moles of Fe₂O₃ (6 × 2/3 = 4), showing how mole ratios serve as conversion factors in stoichiometry!

Question 4

Iron reacts with chlorine to form iron(III) chloride: 2Fe+3Cl2→2FeCl3\mathrm{2Fe + 3Cl_2 \rightarrow 2FeCl_3}. What is the mole ratio of Fe\mathrm{Fe} to Cl2\mathrm{Cl_2}?

  1. 3:23:2
  2. 2:32:3 (correct answer)
  3. 2:12:1
  4. 1:31:3
Explanation: This question tests your understanding that coefficients in balanced chemical equations represent mole ratios—the proportional relationships between amounts of reactants consumed and products formed in a chemical reaction. The coefficients in a balanced equation (the numbers in front of chemical formulas) tell you the ratio of MOLES of each substance involved in the reaction: in 2H2+O2→2H2O2\mathrm{H_2} + \mathrm{O_2} \rightarrow 2\mathrm{H_2O}, the coefficients 2, 1, and 2 mean that 2 moles of hydrogen gas react with 1 mole of oxygen gas to produce 2 moles of water. This ratio is the fundamental relationship—it means for every 1 mole of O2 consumed, exactly 2 moles of H2 are consumed and exactly 2 moles of H2O are produced. The ratio stays constant no matter how much you scale it: 4 moles H2 with 2 moles O2 makes 4 moles H2O (doubled), or 1 mole H2 with 0.5 moles O2 makes 1 mole H2O (halved)—the 2:1:2 ratio is preserved! In the given equation 2Fe+3Cl2→2FeCl32\mathrm{Fe} + 3\mathrm{Cl_2} \rightarrow 2\mathrm{FeCl_3}, the coefficient for Fe is 2 and for Cl2 is 3, so the mole ratio of Fe to Cl2 is 2:3, meaning 2 moles of Fe react with 3 moles of Cl2. Choice B correctly interprets the coefficients as the mole ratio between the specified substances. A distractor like choice A might swap to 3:2, but ensure you list in the asked order—Fe to Cl2 means coefficient of Fe first (2) to Cl2 (3). Reading mole ratios from balanced equations: (1) Locate the two substances you're comparing in the equation. (2) Read their coefficients (the numbers in front—if no number is written, the coefficient is 1). (3) Write the ratio: [coefficient of first substance] : [coefficient of second substance]. Using mole ratios as conversion factors: mole ratios let you predict amounts! If you know how many moles of one substance you have, you can calculate moles of another using the ratio—they're not just decorative numbers, they're the mathematical relationship between substances in the reaction!

Question 5

In the balanced equation Zn+2HCl→ZnCl2+H2\mathrm{Zn + 2HCl \rightarrow ZnCl_2 + H_2} how many moles of HCl\mathrm{HCl} are required to react with 11 mol of Zn\mathrm{Zn}?

  1. 11 mol
  2. 22 mol (correct answer)
  3. 33 mol
  4. 44 mol
Explanation: This question tests your understanding that coefficients in balanced chemical equations represent mole ratios—the proportional relationships between amounts of reactants consumed and products formed in a chemical reaction. The coefficients in a balanced equation (the numbers in front of chemical formulas) tell you the ratio of MOLES of each substance involved in the reaction: in 2H2+O2→2H2O2\mathrm{H_2 + O_2 \rightarrow 2H_2O}, the coefficients 2, 1, and 2 mean that 2 moles of hydrogen gas react with 1 mole of oxygen gas to produce 2 moles of water. This ratio is the fundamental relationship—it means for every 1 mole of O2 consumed, exactly 2 moles of H2 are consumed and exactly 2 moles of H2O are produced. The ratio stays constant no matter how much you scale it: 4 moles H2 with 2 moles O2 makes 4 moles H2O (doubled), or 1 mole H2 with 0.5 moles O2 makes 1 mole H2O (halved)—the 2:1:22:1:2 ratio is preserved! In the given equation Zn+2HCl→ZnCl2+H2\mathrm{Zn + 2HCl \rightarrow ZnCl_2 + H_2}, the coefficient of HCl is 2 and Zn is 1 (implied), so 2 moles of HCl are required for 1 mole of Zn, based on the 1:21:2 ratio of Zn to HCl. Choice B correctly interprets the coefficients as the mole ratio between the specified substances. Choice A could be a mistake if you ignore the coefficient of HCl, but always include the numbers—it's 2, not 1! Reading mole ratios from balanced equations: (1) Locate the two substances you're comparing in the equation. (2) Read their coefficients (the numbers in front—if no number is written, the coefficient is 1). (3) Write the ratio: [coefficient of first substance] : [coefficient of second substance]. Example: from N2+3H2→2NH3\mathrm{N_2 + 3H_2 \rightarrow 2NH_3}, the ratio of N2 to H2 is 1:31:3 (read coefficients 1 and 3). The ratio of H2 to NH3 is 3:23:2 (coefficients 3 and 2). The ratio of N2 to NH3 is 1:21:2 (coefficients 1 and 2). You can find the ratio between ANY two substances in the equation by reading their coefficients! Using mole ratios as conversion factors: mole ratios let you predict amounts! If you know how many moles of one substance you have, you can calculate moles of another using the ratio. From 2H2+O2→2H2O2\mathrm{H_2 + O_2 \rightarrow 2H_2O}, if you have 5 moles of H2, how many moles H2O can form? Ratio H2:H2O is 2:22:2 or 1:11:1, so 5 moles H2 produces 5 moles H2O. If you have 5 moles H2, how many moles O2 needed? Ratio H2:O2 is 2:12:1, so 5 moles H2 needs 2.5 moles O2. The coefficients are your conversion tool—they're not just decorative numbers, they're the mathematical relationship between substances in the reaction!

Question 6

Iron(III) chloride forms by the balanced synthesis equation 2Fe+3Cl2→2FeCl3\mathrm{2Fe + 3Cl_2 \rightarrow 2FeCl_3} What is the mole ratio of Fe\mathrm{Fe} to Cl2\mathrm{Cl_2}?

  1. 3:23:2
  2. 2:32:3 (correct answer)
  3. 2:62:6
  4. 1:11:1
Explanation: This question tests your understanding that coefficients in balanced chemical equations represent mole ratios—the proportional relationships between amounts of reactants consumed and products formed in a chemical reaction. The coefficients in a balanced equation (the numbers in front of chemical formulas) tell you the ratio of MOLES of each substance involved in the reaction: in 2H2+O2→2H2O2\mathrm{H_2} + \mathrm{O_2} \rightarrow 2\mathrm{H_2O}, the coefficients 2, 1, and 2 mean that 2 moles of hydrogen gas react with 1 mole of oxygen gas to produce 2 moles of water. This ratio is the fundamental relationship—it means for every 1 mole of O2 consumed, exactly 2 moles of H2 are consumed and exactly 2 moles of H2O are produced. The ratio stays constant no matter how much you scale it: 4 moles H2 with 2 moles O2 makes 4 moles H2O (doubled), or 1 mole H2 with 0.5 moles O2 makes 1 mole H2O (halved)—the 2:1:22:1:2 ratio is preserved! In the given equation 2Fe+3Cl2→2FeCl32\mathrm{Fe} + 3\mathrm{Cl_2} \rightarrow 2\mathrm{FeCl_3}, the coefficient of Fe is 2 and Cl2 is 3, so the mole ratio of Fe to Cl2 is 2:32:3, meaning 2 moles of Fe react with 3 moles of Cl2. Choice B correctly interprets the coefficients as the mole ratio between the specified substances. Choice A might happen if you swap the order, but the question asks for Fe to Cl2, which is 2:32:3, not 3:23:2—double-check the sequence! Reading mole ratios from balanced equations: (1) Locate the two substances you're comparing in the equation. (2) Read their coefficients (the numbers in front—if no number is written, the coefficient is 1). (3) Write the ratio: [coefficient of first substance] : [coefficient of second substance]. Example: from N2+3H2→2NH3\mathrm{N_2} + 3\mathrm{H_2} \rightarrow 2\mathrm{NH_3}, the ratio of N2 to H2 is 1:31:3 (read coefficients 1 and 3). The ratio of H2 to NH3 is 3:23:2 (coefficients 3 and 2). The ratio of N2 to NH3 is 1:21:2 (coefficients 1 and 2). You can find the ratio between ANY two substances in the equation by reading their coefficients! Using mole ratios as conversion factors: mole ratios let you predict amounts! If you know how many moles of one substance you have, you can calculate moles of another using the ratio. From 2H2+O2→2H2O2\mathrm{H_2} + \mathrm{O_2} \rightarrow 2\mathrm{H_2O}, if you have 5 moles of H2, how many moles H2O can form? Ratio H2:H2O is 2:22:2 or 1:11:1, so 5 moles H2 produces 5 moles H2O. If you have 5 moles H2, how many moles O2 needed? Ratio H2:O2 is 2:12:1, so 5 moles H2 needs 2.5 moles O2. The coefficients are your conversion tool—they're not just decorative numbers, they're the mathematical relationship between substances in the reaction!

Question 7

In the balanced combustion equation CH4+2O2→CO2+2H2O\mathrm{CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O} what is the mole ratio of O2\mathrm{O_2} to CH4\mathrm{CH_4}?

  1. 2:12:1 (correct answer)
  2. 1:21:2
  3. 2:42:4
  4. 4:24:2
Explanation: This question tests your understanding that coefficients in balanced chemical equations represent mole ratios—the proportional relationships between amounts of reactants consumed and products formed in a chemical reaction. The coefficients in a balanced equation (the numbers in front of chemical formulas) tell you the ratio of MOLES of each substance involved in the reaction: in 2H2 + O2 → 2H2O, the coefficients 2, 1, and 2 mean that 2 moles of hydrogen gas react with 1 mole of oxygen gas to produce 2 moles of water. This ratio is the fundamental relationship—it means for every 1 mole of O2 consumed, exactly 2 moles of H2 are consumed and exactly 2 moles of H2O are produced. The ratio stays constant no matter how much you scale it: 4 moles H2 with 2 moles O2 makes 4 moles H2O (doubled), or 1 mole H2 with 0.5 moles O2 makes 1 mole H2O (halved)—the 2:1:2 ratio is preserved! In the given equation CH4 + 2O2 → CO2 + 2H2O, the coefficient of O2 is 2 and CH4 is 1 (implied), so the mole ratio of O2 to CH4 is 2:1, meaning 2 moles of O2 are needed for every 1 mole of CH4. Choice A correctly interprets the coefficients as the mole ratio between the specified substances. Choice B might tempt you if you reverse the order, but remember, the ratio is O2 to CH4, not CH4 to O2—always list them in the order asked! Reading mole ratios from balanced equations: (1) Locate the two substances you're comparing in the equation. (2) Read their coefficients (the numbers in front—if no number is written, the coefficient is 1). (3) Write the ratio: [coefficient of first substance] : [coefficient of second substance]. Example: from N2 + 3H2 → 2NH3, the ratio of N2 to H2 is 1:3 (read coefficients 1 and 3). The ratio of H2 to NH3 is 3:2 (coefficients 3 and 2). The ratio of N2 to NH3 is 1:2 (coefficients 1 and 2). You can find the ratio between ANY two substances in the equation by reading their coefficients! Using mole ratios as conversion factors: mole ratios let you predict amounts! If you know how many moles of one substance you have, you can calculate moles of another using the ratio. From 2H2 + O2 → 2H2O, if you have 5 moles of H2, how many moles H2O can form? Ratio H2:H2O is 2:2 or 1:1, so 5 moles H2 produces 5 moles H2O. If you have 5 moles H2, how many moles O2 needed? Ratio H2:O2 is 2:1, so 5 moles H2 needs 2.5 moles O2. The coefficients are your conversion tool—they're not just decorative numbers, they're the mathematical relationship between substances in the reaction!

Question 8

Rust formation (simplified) can be represented by the balanced equation 4Fe+3O2→2Fe2O3\mathrm{4Fe + 3O_2 \rightarrow 2Fe_2O_3}. What is the mole ratio of Fe\mathrm{Fe} to Fe2O3\mathrm{Fe_2O_3}?

  1. 2:42:4
  2. 4:24:2 (correct answer)
  3. 3:23:2
  4. 2:32:3
Explanation: This question tests your understanding that coefficients in balanced chemical equations represent mole ratios—the proportional relationships between amounts of reactants consumed and products formed in a chemical reaction. The coefficients in a balanced equation (the numbers in front of chemical formulas) tell you the ratio of MOLES of each substance involved in the reaction: in 2H2+O2→2H2O2\mathrm{H_2} + \mathrm{O_2} \rightarrow 2\mathrm{H_2O}, the coefficients 2, 1, and 2 mean that 2 moles of hydrogen gas react with 1 mole of oxygen gas to produce 2 moles of water. This ratio is the fundamental relationship—it means for every 1 mole of O2\mathrm{O_2} consumed, exactly 2 moles of H2\mathrm{H_2} are consumed and exactly 2 moles of H2O\mathrm{H_2O} are produced. The ratio stays constant no matter how much you scale it: 4 moles H2\mathrm{H_2} with 2 moles O2\mathrm{O_2} makes 4 moles H2O\mathrm{H_2O} (doubled), or 1 mole H2\mathrm{H_2} with 0.5 moles O2\mathrm{O_2} makes 1 mole H2O\mathrm{H_2O} (halved)—the 2:1:2 ratio is preserved! In the given equation 4Fe+3O2→2Fe2O34\mathrm{Fe} + 3\mathrm{O_2} \rightarrow 2\mathrm{Fe_2O_3}, the coefficient for Fe is 4 and for Fe2O3 is 2, so the mole ratio of Fe to Fe2O3 is 4:2, meaning 4 moles of Fe produce 2 moles of Fe2O3. Choice B correctly interprets the coefficients as the mole ratio between the specified substances. A distractor like choice A might reverse to 2:4, but list in the order asked—Fe to Fe2O3 means coefficient of Fe first (4) to Fe2O3 (2). Reading mole ratios from balanced equations: (1) Locate the two substances you're comparing in the equation. (2) Read their coefficients (the numbers in front—if no number is written, the coefficient is 1). (3) Write the ratio: [coefficient of first substance] : [coefficient of second substance]. Using mole ratios as conversion factors: mole ratios let you predict amounts! If you know how many moles of one substance you have, you can calculate moles of another using the ratio—they're not just decorative numbers, they're the mathematical relationship between substances in the reaction!

Question 9

Ammonia forms according to N2+3H2→2NH3.\text{N}_2 + 3\text{H}_2 \rightarrow 2\text{NH}_3. What is the mole ratio of NH3\text{NH}_3 to H2\text{H}_2?

  1. 2:3 (correct answer)
  2. 3:2
  3. 2:1
  4. 3:1
Explanation: This question tests your understanding that coefficients in balanced chemical equations represent mole ratios—the proportional relationships between amounts of reactants consumed and products formed in a chemical reaction. The coefficients in a balanced equation (the numbers in front of chemical formulas) tell you the ratio of MOLES of each substance involved in the reaction: in N2+3H2→2NH3\text{N}_2 + 3\text{H}_2 \rightarrow 2\text{NH}_3, the coefficients 1, 3, and 2 mean that 1 mole of nitrogen reacts with 3 moles of hydrogen to produce 2 moles of ammonia. This ratio is the fundamental relationship—it means for every 3 moles of H2\text{H}_2 consumed, exactly 1 mole of N2\text{N}_2 is consumed and 2 moles of NH3\text{NH}_3 are produced. The ratio stays constant no matter how much you scale it: 2 moles of N2\text{N}_2 with 6 moles of H2\text{H}_2 makes 4 moles of NH3\text{NH}_3 (doubled), or 0.5 moles of N2\text{N}_2 with 1.5 moles of H2\text{H}_2 makes 1 mole of NH3\text{NH}_3 (halved)—the 1:3:2 ratio is preserved! In this equation, the mole ratio of NH3\text{NH}_3 to H2\text{H}_2 is extracted from their coefficients: NH3\text{NH}_3 has 2 and H2\text{H}_2 has 3, so it's 2:3, meaning 2 moles of NH3\text{NH}_3 per 3 moles of H2\text{H}_2. Choice A correctly interprets the coefficients as the mole ratio between NH3\text{NH}_3 and H2\text{H}_2, stating 2:3. A distractor like choice B (3:2) might swap the order, but the question specifies NH3\text{NH}_3 to H2\text{H}_2, which is 2:3—pay attention to which comes first. Reading mole ratios from balanced equations: (1) Locate the two substances you're comparing in the equation. (2) Read their coefficients (the numbers in front—if no number is written, the coefficient is 1). (3) Write the ratio: [coefficient of first substance] : [coefficient of second substance]. Using mole ratios as conversion factors: mole ratios let you predict amounts! If you know how many moles of one substance you have, you can calculate moles of another using the ratio.

Question 10

Methane combusts according to CH4+2O2→CO2+2H2O.\text{CH}_4 + 2\text{O}_2 \rightarrow \text{CO}_2 + 2\text{H}_2\text{O}. What is the mole ratio of H2O\text{H}_2\text{O} to CO2\text{CO}_2?

  1. 2:1 (correct answer)
  2. 1:2
  3. 2:2
  4. 1:1
Explanation: This question tests your understanding that coefficients in balanced chemical equations represent mole ratios—the proportional relationships between amounts of reactants consumed and products formed in a chemical reaction. The coefficients in a balanced equation (the numbers in front of chemical formulas) tell you the ratio of MOLES of each substance involved in the reaction: in CH4+2O2→CO2+2H2O\text{CH}_4 + 2\text{O}_2 \rightarrow \text{CO}_2 + 2\text{H}_2\text{O}, the coefficients 1, 2, 1, and 2 mean that 1 mole of CH4\text{CH}_4 reacts with 2 moles of O2\text{O}_2 to produce 1 mole of CO2\text{CO}_2 and 2 moles of H2O\text{H}_2\text{O}. This ratio is the fundamental relationship—it means for every 1 mole of CO2\text{CO}_2 produced, exactly 2 moles of H2O\text{H}_2\text{O} are also produced. The ratio stays constant no matter how much you scale it: 2 moles CH4\text{CH}_4 with 4 moles O2\text{O}_2 makes 2 moles CO2\text{CO}_2 and 4 moles H2O\text{H}_2\text{O} (doubled), or 0.5 moles CH4\text{CH}_4 with 1 mole O2\text{O}_2 makes 0.5 moles CO2\text{CO}_2 and 1 mole H2O\text{H}_2\text{O} (halved)—the 1:2:1:2 ratio is preserved! In this equation, the mole ratio of H2O\text{H}_2\text{O} to CO2\text{CO}_2 is extracted from their coefficients: H2O\text{H}_2\text{O} has 2 and CO2\text{CO}_2 has 1 (implied), so it's 2:1, meaning 2 moles of H2O\text{H}_2\text{O} per 1 mole of CO2\text{CO}_2. Choice A correctly interprets the coefficients as the mole ratio between H2O\text{H}_2\text{O} and CO2\text{CO}_2, stating 2:1. A distractor like choice B (1:2) could be from reversing the substances, but the question asks for H2O\text{H}_2\text{O} to CO2\text{CO}_2—keep the order straight. Reading mole ratios from balanced equations: (1) Locate the two substances you're comparing in the equation. (2) Read their coefficients (the numbers in front—if no number is written, the coefficient is 1). (3) Write the ratio: [coefficient of first substance] : [coefficient of second substance]. Using mole ratios as conversion factors: mole ratios let you predict amounts! If you know how many moles of one substance you have, you can calculate moles of another using the ratio.

Question 11

Hydrogen peroxide decomposes according to the balanced equation 2H2O2→2H2O+O2\mathrm{2H_2O_2 \rightarrow 2H_2O + O_2}. What is the mole ratio of H2O\mathrm{H_2O} produced to O2\mathrm{O_2} produced?

  1. 1:21:2
  2. 2:12:1 (correct answer)
  3. 2:22:2
  4. 1:11:1
Explanation: This question tests your understanding that coefficients in balanced chemical equations represent mole ratios—the proportional relationships between amounts of reactants consumed and products formed in a chemical reaction. The coefficients in a balanced equation (the numbers in front of chemical formulas) tell you the ratio of MOLES of each substance involved in the reaction: in 2H2+O2→2H2O2\mathrm{H_2} + \mathrm{O_2} \rightarrow 2\mathrm{H_2O}, the coefficients 2, 1, and 2 mean that 2 moles of hydrogen gas react with 1 mole of oxygen gas to produce 2 moles of water. This ratio is the fundamental relationship—it means for every 1 mole of O2 consumed, exactly 2 moles of H2 are consumed and exactly 2 moles of H2O are produced. The ratio stays constant no matter how much you scale it: 4 moles H2 with 2 moles O2 makes 4 moles H2O (doubled), or 1 mole H2 with 0.5 moles O2 makes 1 mole H2O (halved)—the 2:1:22:1:2 ratio is preserved! In the given equation 2H2O2→2H2O+O22\mathrm{H_2O_2} \rightarrow 2\mathrm{H_2O} + \mathrm{O_2}, the coefficient for H2O is 2 and for O2 is 1 (implied), so the mole ratio of H2O produced to O2 produced is 2:1, meaning 2 moles of H2O for every 1 mole of O2. Choice B correctly interprets the coefficients as the mole ratio between the specified substances. A distractor like choice A might reverse the order to 1:2, but always match the asked order—H2O to O2 means coefficient of H2O first (2) to O2 (1). Reading mole ratios from balanced equations: (1) Locate the two substances you're comparing in the equation. (2) Read their coefficients (the numbers in front—if no number is written, the coefficient is 1). (3) Write the ratio: [coefficient of first substance] : [coefficient of second substance]. Using mole ratios as conversion factors: mole ratios let you predict amounts! If you know how many moles of one substance you have, you can calculate moles of another using the ratio—they're not just decorative numbers, they're the mathematical relationship between substances in the reaction!

Question 12

For the synthesis of ammonia, the balanced equation is N2+3H2→2NH3\mathrm{N_2 + 3H_2 \rightarrow 2NH_3}. According to the coefficients, how many moles of H2\mathrm{H_2} react per 1 mole of N2\mathrm{N_2}?

  1. 1 mol H2\mathrm{H_2}
  2. 2 mol H2\mathrm{H_2}
  3. 3 mol H2\mathrm{H_2} (correct answer)
  4. 6 mol H2\mathrm{H_2}
Explanation: This question tests your understanding that coefficients in balanced chemical equations represent mole ratios—the proportional relationships between amounts of reactants consumed and products formed in a chemical reaction. The coefficients in a balanced equation (the numbers in front of chemical formulas) tell you the ratio of MOLES of each substance involved in the reaction: in 2H2+O2→2H2O2H2 + O2 \rightarrow 2H2O, the coefficients 2, 1, and 2 mean that 2 moles of hydrogen gas react with 1 mole of oxygen gas to produce 2 moles of water. This ratio is the fundamental relationship—it means for every 1 mole of O2 consumed, exactly 2 moles of H2 are consumed and exactly 2 moles of H2O are produced. The ratio stays constant no matter how much you scale it: 4 moles H2 with 2 moles O2 makes 4 moles H2O (doubled), or 1 mole H2 with 0.5 moles O2 makes 1 mole H2O (halved)—the 2:1:2 ratio is preserved! In the given equation N2+3H2→2NH3N2 + 3H2 \rightarrow 2NH3, the coefficient for H2 is 3 and for N2 is 1, so per 1 mole of N2, 3 moles of H2 react, directly from the 1:3 ratio of N2 to H2. Choice C correctly interprets the coefficients as the mole ratio between the specified substances. A distractor like choice B might misread the ratio as 2 moles from the product side, but focus on the reactant coefficients and the 'per 1 mole of N2' phrasing to avoid confusing it with the NH3 coefficient. Reading mole ratios from balanced equations: (1) Locate the two substances you're comparing in the equation. (2) Read their coefficients (the numbers in front—if no number is written, the coefficient is 1). (3) Write the ratio: [coefficient of first substance] : [coefficient of second substance]. Using mole ratios as conversion factors: mole ratios let you predict amounts! If you know how many moles of one substance you have, you can calculate moles of another using the ratio—they're not just decorative numbers, they're the mathematical relationship between substances in the reaction!

Question 13

Iron reacts with chlorine according to the balanced equation 2Fe+3Cl2→2FeCl3.2\text{Fe} + 3\text{Cl}_2 \rightarrow 2\text{FeCl}_3. What is the mole ratio of Fe\text{Fe} to Cl2\text{Cl}_2?

  1. 3:2
  2. 2:3 (correct answer)
  3. 2:1
  4. 1:1
Explanation: This question tests your understanding that coefficients in balanced chemical equations represent mole ratios—the proportional relationships between amounts of reactants consumed and products formed in a chemical reaction. The coefficients in a balanced equation (the numbers in front of chemical formulas) tell you the ratio of MOLES of each substance involved in the reaction: in 2Fe+3Cl2→2FeCl32\text{Fe} + 3\text{Cl}_2 \rightarrow 2\text{FeCl}_3, the coefficients 2, 3, and 2 mean that 2 moles of Fe\text{Fe} react with 3 moles of Cl2\text{Cl}_2 to produce 2 moles of FeCl3\text{FeCl}_3. This ratio is the fundamental relationship—it means for every 2 moles of Fe\text{Fe} consumed, exactly 3 moles of Cl2\text{Cl}_2 are consumed and 2 moles of FeCl3\text{FeCl}_3 are produced. The ratio stays constant no matter how much you scale it: 4 moles Fe\text{Fe} with 6 moles Cl2\text{Cl}_2 makes 4 moles FeCl3\text{FeCl}_3 (doubled), or 1 mole Fe\text{Fe} with 1.5 moles Cl2\text{Cl}_2 makes 1 mole FeCl3\text{FeCl}_3 (halved)—the 2:3:22:3:2 ratio is preserved! In this equation, the mole ratio of Fe\text{Fe} to Cl2\text{Cl}_2 is extracted from their coefficients: Fe\text{Fe} has 2 and Cl2\text{Cl}_2 has 3, so it's 2:32:3, meaning 2 moles of Fe\text{Fe} per 3 moles of Cl2\text{Cl}_2. Choice B correctly interprets the coefficients as the mole ratio between Fe\text{Fe} and Cl2\text{Cl}_2, stating 2:32:3. A distractor like choice A (3:23:2) might reverse the substances, but confirm the order: it's Fe\text{Fe} to Cl2\text{Cl}_2, which is 2:32:3, not 3:23:2. Reading mole ratios from balanced equations: (1) Locate the two substances you're comparing in the equation. (2) Read their coefficients (the numbers in front—if no number is written, the coefficient is 1). (3) Write the ratio: [coefficient of first substance] : [coefficient of second substance]. Using mole ratios as conversion factors: mole ratios let you predict amounts! If you know how many moles of one substance you have, you can calculate moles of another using the ratio.

Question 14

Water forms from hydrogen and oxygen as shown in the balanced equation 2H2+O2→2H2O.2\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O}. Which statement correctly describes the mole relationship between O2\text{O}_2 and H2O\text{H}_2\text{O}?

  1. 1 mol O2\text{O}_2 produces 1 mol H2O\text{H}_2\text{O}
  2. 2 mol O2\text{O}_2 produces 1 mol H2O\text{H}_2\text{O}
  3. 1 mol O2\text{O}_2 produces 2 mol H2O\text{H}_2\text{O} (correct answer)
  4. 2 mol O2\text{O}_2 produces 2 mol H2O\text{H}_2\text{O}
Explanation: This question tests your understanding that coefficients in balanced chemical equations represent mole ratios—the proportional relationships between amounts of reactants consumed and products formed in a chemical reaction. The coefficients in a balanced equation (the numbers in front of chemical formulas) tell you the ratio of MOLES of each substance involved in the reaction: in 2H2+O2→2H2O2\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O}, the coefficients 2, 1, and 2 mean that 22 moles of H2\text{H}_2 react with 11 mole of O2\text{O}_2 to produce 22 moles of H2O\text{H}_2\text{O}. This ratio is the fundamental relationship—it means for every 11 mole of O2\text{O}_2 consumed, exactly 22 moles of H2\text{H}_2 are consumed and exactly 22 moles of H2O\text{H}_2\text{O} are produced. The ratio stays constant no matter how much you scale it: 44 moles of H2\text{H}_2 with 22 moles of O2\text{O}_2 makes 44 moles of H2O\text{H}_2\text{O} (doubled), or 11 mole of H2\text{H}_2 with 0.50.5 moles of O2\text{O}_2 makes 11 mole of H2O\text{H}_2\text{O} (halved)—the 2:1:22:1:2 ratio is preserved! In this equation, the mole relationship between O2\text{O}_2 and H2O\text{H}_2\text{O} is that 11 mole of O2\text{O}_2 produces 22 moles of H2O\text{H}_2\text{O}, as their coefficients are 1 and 2. Choice C correctly interprets the coefficients by stating 1 mol O2\text{O}_2 produces 2 mol H2O\text{H}_2\text{O}. A distractor like choice A (1 mol O2\text{O}_2 produces 1 mol H2O\text{H}_2\text{O}) might ignore the coefficients, but remember, the numbers show the proportion—O2\text{O}_2's 1 to H2O\text{H}_2\text{O}'s 2 means twice as much water is produced. Reading mole ratios from balanced equations: (1) Locate the two substances you're comparing in the equation. (2) Read their coefficients (the numbers in front—if no number is written, the coefficient is 1). (3) Write the ratio: [coefficient of first substance] : [coefficient of second substance]. Using mole ratios as conversion factors: mole ratios let you predict amounts! If you know how many moles of one substance you have, you can calculate moles of another using the ratio.

Question 15

Iron(III) oxide forms according to the balanced equation 4Fe+3O2→2Fe2O3\mathrm{4Fe + 3O_2 \rightarrow 2Fe_2O_3} What is the mole ratio of Fe2O3\mathrm{Fe_2O_3} to O2\mathrm{O_2}?

  1. 3:23:2
  2. 2:32:3 (correct answer)
  3. 4:34:3
  4. 2:42:4
Explanation: This question tests your understanding that coefficients in balanced chemical equations represent mole ratios—the proportional relationships between amounts of reactants consumed and products formed in a chemical reaction. The coefficients in a balanced equation (the numbers in front of chemical formulas) tell you the ratio of MOLES of each substance involved in the reaction: in 2H2+O2→2H2O\mathrm{2H_2 + O_2 \rightarrow 2H_2O}, the coefficients 2, 1, and 2 mean that 2 moles of hydrogen gas react with 1 mole of oxygen gas to produce 2 moles of water. This ratio is the fundamental relationship—it means for every 1 mole of O2 consumed, exactly 2 moles of H2 are consumed and exactly 2 moles of H2O are produced. The ratio stays constant no matter how much you scale it: 4 moles H2 with 2 moles O2 makes 4 moles H2O (doubled), or 1 mole H2 with 0.5 moles O2 makes 1 mole H2O (halved)—the 2:1:22:1:2 ratio is preserved! In the given equation 4Fe+3O2→2Fe2O3\mathrm{4Fe + 3O_2 \rightarrow 2Fe_2O_3}, the coefficient of Fe2O3 is 2 and O2 is 3, so the mole ratio of Fe2O3 to O2 is 2:32:3, meaning 2 moles of Fe2O3 form from 3 moles of O2. Choice B correctly interprets the coefficients as the mole ratio between the specified substances. Choice A might confuse you if you reverse it, but the order is Fe2O3 to O2, so 2:3, not 3:2—keep the sequence straight! Reading mole ratios from balanced equations: (1) Locate the two substances you're comparing in the equation. (2) Read their coefficients (the numbers in front—if no number is written, the coefficient is 1). (3) Write the ratio: [coefficient of first substance] : [coefficient of second substance]. Example: from N2+3H2→2NH3\mathrm{N_2 + 3H_2 \rightarrow 2NH_3}, the ratio of N2 to H2 is 1:31:3 (read coefficients 1 and 3). The ratio of H2 to NH3 is 3:23:2 (coefficients 3 and 2). The ratio of N2 to NH3 is 1:21:2 (coefficients 1 and 2). You can find the ratio between ANY two substances in the equation by reading their coefficients! Using mole ratios as conversion factors: mole ratios let you predict amounts! If you know how many moles of one substance you have, you can calculate moles of another using the ratio. From 2H2+O2→2H2O\mathrm{2H_2 + O_2 \rightarrow 2H_2O}, if you have 5 moles of H2, how many moles H2O can form? Ratio H2:H2O is 2:22:2 or 1:11:1, so 5 moles H2 produces 5 moles H2O. If you have 5 moles H2, how many moles O2 needed? Ratio H2:O2 is 2:12:1, so 5 moles H2 needs 2.5 moles O2. The coefficients are your conversion tool—they're not just decorative numbers, they're the mathematical relationship between substances in the reaction!

Question 16

Hydrogen peroxide decomposes as shown: 2H2O2→2H2O+O2\mathrm{2H_2O_2 \rightarrow 2H_2O + O_2} What is the mole ratio of hydrogen peroxide (H2O2\mathrm{H_2O_2}) to oxygen gas (O2\mathrm{O_2})?

  1. 1:21:2
  2. 2:12:1 (correct answer)
  3. 2:22:2
  4. 2:42:4
Explanation: This question tests your understanding that coefficients in balanced chemical equations represent mole ratios—the proportional relationships between amounts of reactants consumed and products formed in a chemical reaction. The coefficients in a balanced equation (the numbers in front of chemical formulas) tell you the ratio of MOLES of each substance involved in the reaction: in 2H₂O₂ → 2H₂O + O₂, the coefficients 2, 2, and 1 mean that 2 moles of hydrogen peroxide decompose to produce 2 moles of water and 1 mole of oxygen gas. From the equation 2H₂O₂ → 2H₂O + O₂, to find the ratio of hydrogen peroxide (H₂O₂) to oxygen gas (O₂), I locate H₂O₂ with coefficient 2 and O₂ with coefficient 1 (when no number is shown, it's 1), giving the ratio 2:1. Choice B correctly identifies this 2:1 ratio, meaning for every 2 moles of H₂O₂ that decompose, 1 mole of O₂ is produced. The other choices incorrectly reverse the ratio (1:2), suggest equal amounts (2:2), or create an impossible ratio (2:4) not supported by the coefficients. Reading mole ratios from balanced equations: (1) Locate the two substances you're comparing in the equation. (2) Read their coefficients (the numbers in front—if no number is written, the coefficient is 1). (3) Write the ratio: [coefficient of first substance] : [coefficient of second substance]. This 2:1 ratio is a powerful tool: if 10 moles of H₂O₂ decompose, you know exactly 5 moles of O₂ will form (10 ÷ 2 = 5), demonstrating how coefficients provide the mathematical relationship for predicting amounts in chemical reactions!

Question 17

Zinc reacts with hydrochloric acid according to: Zn+2HCl→ZnCl2+H2\mathrm{Zn + 2HCl \rightarrow ZnCl_2 + H_2} What is the mole ratio of hydrochloric acid (HCl\mathrm{HCl}) to hydrogen gas (H2\mathrm{H_2})?

  1. 1:21:2
  2. 2:12:1 (correct answer)
  3. 2:22:2
  4. 1:11:1
Explanation: This question tests your understanding that coefficients in balanced chemical equations represent mole ratios—the proportional relationships between amounts of reactants consumed and products formed in a chemical reaction. The coefficients in a balanced equation (the numbers in front of chemical formulas) tell you the ratio of MOLES of each substance involved in the reaction: in Zn + 2HCl → ZnCl₂ + H₂, the coefficients 1, 2, 1, and 1 mean that 1 mole of zinc reacts with 2 moles of hydrochloric acid to produce 1 mole of zinc chloride and 1 mole of hydrogen gas. From the equation Zn + 2HCl → ZnCl₂ + H₂, to find the ratio of hydrochloric acid (HCl) to hydrogen gas (H₂), I locate HCl with coefficient 2 and H₂ with coefficient 1 (when no number is shown, it's 1), giving the ratio 2:1. Choice B correctly identifies this 2:1 ratio, meaning for every 2 moles of HCl consumed, 1 mole of H₂ is produced. The other choices incorrectly reverse the ratio (1:2), suggest equal amounts (2:2 or 1:1), failing to recognize the actual coefficient relationship. Reading mole ratios from balanced equations: (1) Locate the two substances you're comparing in the equation. (2) Read their coefficients (the numbers in front—if no number is written, the coefficient is 1). (3) Write the ratio: [coefficient of first substance] : [coefficient of second substance]. This 2:1 ratio has practical applications: if you react 8 moles of HCl, you'll produce 4 moles of H₂ gas (8 ÷ 2 = 4), demonstrating how coefficients allow precise predictions of product amounts from reactant quantities!

Question 18

Ammonia forms from nitrogen and hydrogen: N2+3H2→2NH3\mathrm{N_2 + 3H_2 \rightarrow 2NH_3} If the reaction uses 1 mol of nitrogen gas (N2\mathrm{N_2}), how many moles of hydrogen gas (H2\mathrm{H_2}) are required to match the coefficient ratio?

  1. 1 mol H2\mathrm{H_2}
  2. 2 mol H2\mathrm{H_2}
  3. 3 mol H2\mathrm{H_2} (correct answer)
  4. 6 mol H2\mathrm{H_2}
Explanation: This question tests your understanding that coefficients in balanced chemical equations represent mole ratios—the proportional relationships between amounts of reactants consumed and products formed in a chemical reaction. The coefficients in a balanced equation (the numbers in front of chemical formulas) tell you the ratio of MOLES of each substance involved in the reaction: in N₂ + 3H₂ → 2NH₃, the coefficients 1, 3, and 2 mean that 1 mole of nitrogen gas reacts with 3 moles of hydrogen gas to produce 2 moles of ammonia. From the equation N₂ + 3H₂ → 2NH₃, the coefficient of N₂ is 1 (when no number is shown, it's 1) and the coefficient of H₂ is 3, establishing a 1:3 ratio between nitrogen and hydrogen gas. Choice C correctly states that 3 mol H₂ are required per 1 mol N₂, directly matching the coefficient ratio in the balanced equation. The other choices suggest incorrect amounts (1 mol, 2 mol, or 6 mol), failing to recognize that the coefficients dictate exactly 3 moles of H₂ per mole of N₂. Reading mole ratios from balanced equations: (1) Locate the two substances you're comparing in the equation. (2) Read their coefficients (the numbers in front—if no number is written, the coefficient is 1). (3) Write the ratio: [coefficient of first substance] : [coefficient of second substance]. This 1:3 ratio is crucial for the Haber process: industrial ammonia production requires precisely 3 moles of hydrogen for every mole of nitrogen to maintain the stoichiometric balance and maximize yield!

Question 19

Magnesium reacts with oxygen to form magnesium oxide: 2Mg+O2→2MgO\mathrm{2Mg + O_2 \rightarrow 2MgO} Which mole ratio correctly compares magnesium (Mg\mathrm{Mg}) to oxygen gas (O2\mathrm{O_2})?

  1. 1:21:2
  2. 2:12:1 (correct answer)
  3. 2:22:2
  4. 1:11:1
Explanation: This question tests your understanding that coefficients in balanced chemical equations represent mole ratios—the proportional relationships between amounts of reactants consumed and products formed in a chemical reaction. The coefficients in a balanced equation (the numbers in front of chemical formulas) tell you the ratio of MOLES of each substance involved in the reaction: in 2Mg + O₂ → 2MgO, the coefficients 2, 1, and 2 mean that 2 moles of magnesium react with 1 mole of oxygen gas to produce 2 moles of magnesium oxide. From the equation 2Mg + O₂ → 2MgO, to find the ratio of magnesium (Mg) to oxygen gas (O₂), I locate Mg with coefficient 2 and O₂ with coefficient 1 (when no number is shown, it's 1), giving the ratio 2:1. Choice B correctly identifies this 2:1 ratio, meaning for every 2 moles of Mg that react, 1 mole of O₂ is consumed. The other choices incorrectly reverse the ratio (1:2), suggest equal amounts (2:2 or 1:1), failing to recognize the actual 2:1 relationship from the coefficients. Reading mole ratios from balanced equations: (1) Locate the two substances you're comparing in the equation. (2) Read their coefficients (the numbers in front—if no number is written, the coefficient is 1). (3) Write the ratio: [coefficient of first substance] : [coefficient of second substance]. This 2:1 ratio reflects the chemical reality: each O₂ molecule (with 2 oxygen atoms) can oxidize exactly 2 Mg atoms, forming 2 MgO formula units—the coefficients encode the atomic-level stoichiometry!

Question 20

Iron reacts with chlorine to form iron(III) chloride: 2Fe+3Cl2→2FeCl3\mathrm{2Fe + 3Cl_2 \rightarrow 2FeCl_3} Which statement correctly describes the mole relationship between iron (Fe\mathrm{Fe}) and chlorine gas (Cl2\mathrm{Cl_2})?

  1. For every 2 mol Fe\mathrm{Fe}, 3 mol Cl2\mathrm{Cl_2} react. (correct answer)
  2. For every 3 mol Fe\mathrm{Fe}, 2 mol Cl2\mathrm{Cl_2} react.
  3. For every 2 mol Fe\mathrm{Fe}, 2 mol Cl2\mathrm{Cl_2} react.
  4. For every 1 mol Fe\mathrm{Fe}, 3 mol Cl2\mathrm{Cl_2} react.
Explanation: This question tests your understanding that coefficients in balanced chemical equations represent mole ratios—the proportional relationships between amounts of reactants consumed and products formed in a chemical reaction. The coefficients in a balanced equation (the numbers in front of chemical formulas) tell you the ratio of MOLES of each substance involved in the reaction: in 2Fe + 3Cl₂ → 2FeCl₃, the coefficients 2, 3, and 2 mean that 2 moles of iron react with 3 moles of chlorine gas to produce 2 moles of iron(III) chloride. From the equation 2Fe + 3Cl₂ → 2FeCl₃, the coefficient of Fe is 2 and the coefficient of Cl₂ is 3, establishing a 2:3 ratio between iron and chlorine gas. Choice A correctly interprets this ratio: "For every 2 mol Fe, 3 mol Cl₂ react," which directly matches the coefficients in the balanced equation. The other choices incorrectly reverse the ratio (3:2), suggest equal amounts (2:2), or propose an incorrect ratio (1:3) that doesn't match the coefficients. Reading mole ratios from balanced equations: (1) Locate the two substances you're comparing in the equation. (2) Read their coefficients (the numbers in front—if no number is written, the coefficient is 1). (3) Write the ratio: [coefficient of first substance] : [coefficient of second substance]. The 2:3 ratio means the reaction always maintains this proportion: 4 moles Fe needs 6 moles Cl₂ (doubled), or 1 mole Fe needs 1.5 moles Cl₂ (halved)—the coefficients ensure the reaction proceeds with the correct stoichiometric amounts!