Representations of Reactions - AP Chemistry

1. Balance the equation: $\text{KClO}_3 \rightarrow \text{KCl} + \text{O}_2$

   $2 \text{KClO}_3 \rightarrow 2 \text{KCl} + 3 \text{O}_2$. Balance potassium and chlorine first, then oxygen.

2. What is the symbol for a catalyst in a chemical equation?

   Above the arrow. Catalysts are written above the reaction arrow.

3. State the formula for the combustion reaction of ethanol: $\text{C}_2\text{H}_5\text{OH}$

   $\text{C}_2\text{H}_5\text{OH} + 3 \text{O}_2 \rightarrow 2 \text{CO}_2 + 3 \text{H}_2\text{O}$. Complete combustion of alcohol produces $\text{CO}_2$ and $\text{H}_2\text{O}$.

4. What does a balanced chemical equation represent?

   Equal number of each type of atom on both sides. Atoms are conserved - same number before and after reaction.

5. What is the result of combustion reactions in terms of energy?

   Exothermic process. Combustion releases energy as heat and light.

6. What is the product of a complete combustion of hydrocarbons?

   $\text{CO}_2$ and $\text{H}_2\text{O}$. Complete oxidation yields only these two products.

7. What type of reaction is $\text{AB} \rightarrow \text{A} + \text{B}$?

   Decomposition reaction. One compound breaks down into two or more simpler substances.

8. Balance the equation: $\text{Fe} + \text{O}_2 \rightarrow \text{Fe}_2\text{O}_3$

   $4 \text{Fe} + 3 \text{O}_2 \rightarrow 2 \text{Fe}_2\text{O}_3$. Balance iron atoms first, then oxygen atoms last.

9. Which type of reaction involves the breaking down of a compound into simpler substances?

   Decomposition reaction. Single reactant splits into multiple products.

10. What is the role of a catalyst in a chemical reaction?

    Speeds up the reaction without being consumed. Lowers activation energy but remains unchanged after reaction.

11. Identify the state of matter for $H_2O (l)$ in a chemical equation.

    Liquid. The $(l)$ symbol specifically denotes liquid state.

12. What is the balanced equation for the reaction between $\text{HCl}$ and $\text{NaOH}$?

    $\text{HCl} + \text{NaOH} \rightarrow \text{NaCl} + \text{H}_2\text{O}$. Acid-base neutralization produces salt and water.

13. Which symbol in a chemical equation indicates a liquid state?

    $(l)$. Standard notation for liquid phase in chemical equations.

14. Which symbol in a chemical equation indicates a gaseous state?

    $(g)$. Standard notation for gas phase in chemical equations.

15. Identify the reactants in the reaction: $2 \text{Na} + \text{Cl}_2 \rightarrow 2 \text{NaCl}$

    $2 \text{Na}$, $\text{Cl}_2$. Starting materials that undergo chemical change.

16. What is the result of a precipitation reaction?

    Formation of an insoluble solid. Creates a precipitate that settles out of solution.

17. What does the term 'stoichiometry' refer to in chemical reactions?

    Quantitative relationships between reactants and products. Mathematical ratios between substances in balanced equations.

18. In the reaction $\text{A} + \text{B} \rightarrow \text{C}$, identify the reactants.

    $\text{A}$, $\text{B}$. Reactants appear on the left side of the equation.

19. What is the product of the neutralization reaction between $\text{H}_2\text{SO}_4$ and $\text{KOH}$?

    $\text{K}_2\text{SO}_4$ and $\text{H}_2\text{O}$. Acid neutralization forms salt plus water.

20. What is indicated by a double-headed arrow in a chemical equation?

    Reversible reaction. Equilibrium arrows show reaction can proceed in both directions.

21. What type of reaction is $\text{C}_6\text{H}_{12}\text{O}_6 + 6 \text{O}_2 \rightarrow 6 \text{CO}_2 + 6 \text{H}_2\text{O}$?

    Combustion reaction. Glucose burns in oxygen to produce energy.

22. Identify the coefficients in the equation: $2 \text{H}_2 + \text{O}_2 \rightarrow 2 \text{H}_2\text{O}$

    2, 1, 2. Coefficients balance atoms: 4H, 2O on left equals 4H, 2O on right.

23. What type of reaction is $2 \text{H}_2 + \text{O}_2 \rightarrow 2 \text{H}_2\text{O}$?

    Combination reaction. Two elements combine to form a single compound.

24. What type of reaction is $\text{CaCO}_3 \rightarrow \text{CaO} + \text{CO}_2$?

    Decomposition reaction. Calcium carbonate breaks down into two simpler compounds.

25. Which symbol in a chemical equation indicates a solid state?

    $(s)$. Standard notation for solid phase in chemical equations.

26. Identify the type of reaction: $\text{AgNO}_3 + \text{NaCl} \rightarrow \text{AgCl} + \text{NaNO}_3$

    Double replacement reaction. Cations and anions exchange between the two compounds.

27. Which type of reaction involves the exchange of ions between two compounds?

    Double replacement reaction. Positive and negative ions switch partners between compounds.

28. State the law that requires chemical equations to be balanced.

    Law of Conservation of Mass. Matter cannot be created or destroyed in chemical reactions.

29. Identify the products in the combustion of methane: $\text{CH}_4 + 2 \text{O}_2 \rightarrow \text{CO}_2 + 2 \text{H}_2\text{O}$

    $\text{CO}_2$, $2 \text{H}_2\text{O}$. Complete combustion produces carbon dioxide and water.

30. What type of reaction is $\text{AB} + \text{CD} \rightarrow \text{AD} + \text{CB}$?

    Double replacement reaction. Both compounds exchange their positive and negative ions.

31. What type of reaction is $\text{Zn} + 2 \text{HCl} \rightarrow \text{ZnCl}_2 + \text{H}_2$?

    Single replacement reaction. Zinc displaces hydrogen from hydrochloric acid.

32. Which symbol in a chemical equation indicates an aqueous solution?

    $(aq)$. Indicates dissolved in water solution.

33. Identify the type of reaction: $\text{H}_2 + \text{Cl}_2 \rightarrow 2 \text{HCl}$

    Combination reaction. Two elements combine to form one compound.

34. What does the Δ symbol above the arrow in a chemical equation indicate?

    Heat is applied. Delta indicates thermal energy is required for the reaction.

35. What is the general form of a chemical equation?

    $\text{Reactants} \rightarrow \text{Products}$. Shows direction from starting materials to final products.

36. Balance the equation: $\text{C}_3\text{H}_8 + \text{O}_2 \rightarrow \text{CO}_2 + \text{H}_2\text{O}$

    $\text{C}_3\text{H}_8 + 5 \text{O}_2 \rightarrow 3 \text{CO}_2 + 4 \text{H}_2\text{O}$. Balance carbon first (3), then hydrogen (8), finally oxygen (10).

37. What is meant by 'reaction stoichiometry'?

    Proportional relationships in a balanced equation. Molar ratios from coefficients in balanced equations.

38. What type of reaction is $\text{A} + \text{BC} \rightarrow \text{AC} + \text{B}$?

    Single replacement reaction. One element replaces another in a compound.

39. What is the balanced equation for the synthesis of water from $\text{H}_2$ and $\text{O}_2$?

    $2 \text{H}_2 + \text{O}_2 \rightarrow 2 \text{H}_2\text{O}$. Combination of hydrogen and oxygen gases forms water.

40. State the formula for the synthesis of ammonia: $\text{N}_2 + \text{H}_2$

    $\text{N}_2 + 3 \text{H}_2 \rightarrow 2 \text{NH}_3$. Haber process combines nitrogen and hydrogen gases.

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