ACT Science : How to find synthesis of data in chemistry

Study concepts, example questions & explanations for ACT Science

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Example Questions

Example Question #811 : Act Science

A brilliant but underpaid high school chemistry teacher, together with his former student, manufactures a chemical compound, which they sell for a large mark-up. Their set of reactions are given below:

(1) A + B + C + acid --> D

(2) D --> intermediate

(3) Intermediate --> E

(4) E + acid --> X

His student notes the following observations:

Observation 1) If a greater amount of B and C are used in the reaction, this yields no increased amount of product D.

Observation 2) At any given point, D, the intermediate, and E may co-exist in equal proportions. However, at higher temperatures, higher proportions of product E are noted.

Observation 3) The addition of a strong base can reverse reaction 4.

Adding a strong base will have which of the following effects?

(I) Convert X into E.

(II) Limit the amount of D formed in reaction 1.

(III) Convert E into D.

(IV) No effects.

Possible Answers:

III

I and II

I and III

II and III

IV

Correct answer:

I and II

Explanation:

Observation III indicates that adding a base can convert X back into E, thus reversing the reaction. If adding a base nullifies the actions of an acid in reaction 4, it can also be inferred that it can have the same effect in reaction I. Therefore, options I and II are correct. Option IV can automatically be ruled out because there is an effect of adding a strong base. There is no information suggesting that adding a base will convert E back into D, as option III suggests.

Example Question #31 : How To Find Synthesis Of Data In Chemistry

A brilliant but underpaid high school chemistry teacher, together with his former student, manufactures a chemical compound, which they sell for a large mark-up. Their set of reactions are given below:

(1) A + B + C + acid --> D

(2) D --> intermediate

(3) Intermediate --> E

(4) E + acid --> X

His student notes the following observations:

Observation 1) If a greater amount of B and C are used in the reaction, this yields no increased amount of product D.

Observation 2) At any given point, D, the intermediate, and E may co-exist in equal proportions. However, at higher temperatures, higher proportions of product E are noted.

Observation 3) The addition of a strong base can reverse reaction 4.

Reagents B and C are relatively inexpensive compared to A. What can be expected if twice the number of moles of B and C are used in reaction 1 with the number of moles of A held constant?

Possible Answers:

Twice the amount of D produced

Half the amount of D produced

Four times the amount of D produced

No change in in the amount of D produced

Eight times the amount of D produced

Correct answer:

No change in in the amount of D produced

Explanation:

Observation 1 states that adding additional B or C has no effect in increased yield of D. From this statment, we can infer that reagent A is the "limiting reagent." In other words, the amount of D formed is entirely dependent on the amount of A available; therefore, doubling the amount of number of moles of B and C will not increase or decrease the amount of D formed.

Example Question #31 : How To Find Synthesis Of Data In Chemistry

A brilliant but underpaid high school chemistry teacher, together with his former student, manufactures a chemical compound, which they sell for a large mark-up. Their set of reactions are given below:

(1) A + B + C + acid --> D

(2) D --> intermediate

(3) Intermediate --> E

(4) E + acid --> X

His student notes the following observations:

Observation 1) If a greater amount of B and C are used in the reaction, this yields no increased amount of product D.

Observation 2) At any given point, D, the intermediate, and E may co-exist in equal proportions. However, at higher temperatures, higher proportions of product E are noted.

Observation 3) The addition of a strong base can reverse reaction 4.

Without the addition of acid, reactions 1 and 4 proceed at a much slower rate. What is the role of acid in these reactions?

Possible Answers:

A catalyst; the acid lowers the activation energy of these reactions and helps them proceed more quickly.

An additive; the acid shifts the equilbrium constants of these reactions to produce more product.

No role in these reactions.

A reagent (or substrate); the acid is needed as reagent for completion of these reactions.

Correct answer:

A catalyst; the acid lowers the activation energy of these reactions and helps them proceed more quickly.

Explanation:

The acid can be thought of as a catalyst. The question states that these reactions can proceed without acid, but at a much slower rate; therefore, acid is not needed for these reactions and is not a reagent or substrate; however, its presence will speed the rate of the reactions. Catalysts do not alter the equilibirum constant of a reaction. In other words, they will change the speed or rate of which product is produced, but once the reaction has carried out to completion and each agent is in equilibirum, there will not be relatively more product present because of the acid.

Example Question #811 : Act Science

A brilliant but underpaid high school chemistry teacher, together with his former student, manufactures a chemical compound, which they sell for a large mark-up. Their set of reactions are given below:

(1) A + B + C + acid --> D

(2) D --> intermediate

(3) Intermediate --> E

(4) E + acid --> X

His student notes the following observations:

Observation 1) If a greater amount of B and C are used in the reaction, this yields no increased amount of product D.

Observation 2) At any given point, D, the intermediate, and E may co-exist in equal proportions. However, at higher temperatures, higher proportions of product E are noted.

Observation 3) The addition of a strong base can reverse reaction 4.

If reaction 4 is conducted in isolation, removing some of the product, X, will have which of the following effects?

Possible Answers:

Similar effect to adding more of E

No effect

Decreasing the amount of X subsequently produced

Help reverse the reaction and convert more of the remaining X back into E

Correct answer:

Similar effect to adding more of E

Explanation:

This question asks you to understand the concept of Le Chatelier's Principle, which states that either adding more reagents or removing more product will shift the reaction to the right, and produce more product. By removing X, you will achieve the same affect of adding more of E. Conceptually, this principle can be thought of as a reaction trying to go back to its original state. If product is removed, the reaction will try to replace that product, and thus form more of it.

Example Question #32 : How To Find Synthesis Of Data In Chemistry

A student wished to study the acidity and basicity of various household ingredients and chemicals using her own, homemade pH indicator. A pH indicator is a substance that changes colors to indicate the acidity or basicity of a chemical solution. Acids can be defined as substances that donate hydrogen ions, or H+, while bases are substances that accept H­+ ions. The strength of these acids and bases can be measured using the pH scale as shown in Figure 1.

Figure_1_ph

Experiment 1:

The student placed a leaf of red cabbage in a blender with one liter of water and blended until the cabbage had been liquefied. She then strained the purple mixture and bottled it. The student then added one drop of her homemade cabbage pH indicator to a variety of household chemicals listed in Table 1. She recorded the known pH of these chemicals as well as the color the indicator turned when added to these chemicals.

Table_1_ph

Experiment 2:

The student wanted to see how baking soda would react in the presence of other household chemicals. She combined baking soda in water separately with each of the other chemicals used in Experiment 1. Some combinations would create bubbling while some other combinations wouldn't. She recorded the results in Table 2 below.

                                Table_2_ph

What can be inferred from Experiment 2?

Possible Answers:

Baking soda only produces bubbles in the presence of an acid.

None of the other answers is correct.

Baking soda only produces bubbles in the presence of a base.

Baking soda only produces bubbles in the presence of a chemical with a neutral pH.

Correct answer:

Baking soda only produces bubbles in the presence of an acid.

Explanation:

Baking soda reacts, or produces bubbles, with lemon juice, vinegar, toilet bowl cleaner, and soda pop only. By cross-referencing Table 1, we see that these substances have a pH of less than 7, which is the definition of an acid as Figure 1 shows. Thus, we know that baking soda only reacts with acids.

Example Question #31 : How To Find Synthesis Of Data In Chemistry

A student wished to study the acidity and basicity of various household ingredients and chemicals using her own, homemade pH indicator. A pH indicator is a substance that changes colors to indicate the acidity or basicity of a chemical solution. Acids can be defined as substances that donate hydrogen ions, or H+, while bases are substances that accept H­+ ions. The strength of these acids and bases can be measured using the pH scale as shown in Figure 1.

Figure_1_ph

Experiment 1:

The student placed a leaf of red cabbage in a blender with one liter of water and blended until the cabbage had been liquefied. She then strained the purple mixture and bottled it. The student then added one drop of her homemade cabbage pH indicator to a variety of household chemicals listed in Table 1. She recorded the known pH of these chemicals as well as the color the indicator turned when added to these chemicals.

Table_1_ph

Experiment 2:

The student wanted to see how baking soda would react in the presence of other household chemicals. She combined baking soda in water separately with each of the other chemicals used in Experiment 1. Some combinations would create bubbling while some other combinations wouldn't. She recorded the results in Table 2 below.

                                Table_2_ph

A new indicator, called Methyl Red, is also used to test the household chemicals from Experiments 1 and 2. It is found that the indicator turns red in the presence of toilet bowl cleaner, soda pop, or lemon juice; it turns orange in the presence of vinegar; it turns yellow in the presence of the rest of the chemicals. Which of the following pH ranges most likely contain the pH value at which Methyl Red has its color transition, or pH at which the indicator will stop being red and change to yellow?

Possible Answers:

Correct answer:

Explanation:

It appears that the color transition happens at the pH range around the pH of vinegar, given that the indicator in vinegar is orange, and orange is produced by a combination of red and yellow. As the pH of vinegar, according to Table 1, is 4.5, the range of 4 to 6 is the correct answer as it contains the value.

Example Question #32 : How To Find Synthesis Of Data In Chemistry

A student wished to study the acidity and basicity of various household ingredients and chemicals using her own, homemade pH indicator. A pH indicator is a substance that changes colors to indicate the acidity or basicity of a chemical solution. Acids can be defined as substances that donate hydrogen ions, or H+, while bases are substances that accept H­+ ions. The strength of these acids and bases can be measured using the pH scale as shown in Figure 1.

Figure_1_ph

Experiment 1:

The student placed a leaf of red cabbage in a blender with one liter of water and blended until the cabbage had been liquefied. She then strained the purple mixture and bottled it. The student then added one drop of her homemade cabbage pH indicator to a variety of household chemicals listed in Table 1. She recorded the known pH of these chemicals as well as the color the indicator turned when added to these chemicals.

Table_1_ph

Experiment 2:

The student wanted to see how baking soda would react in the presence of other household chemicals. She combined baking soda in water separately with each of the other chemicals used in Experiment 1. Some combinations would create bubbling while some other combinations wouldn't. She recorded the results in Table 2 below.

                                Table_2_ph

A universal indicator is a pH indicator that is a mix of several different indicators that have distinct color changes in various ranges of the pH scale in order to precisely tell the pH of any solution. While the red cabbage indictor is a good indicator for most pHs, it has one range that does not have drastic enough color changes to precisely tell the pH within this region. What pH range should a supplemental indicator have drastic colors changes in to improve the red cabbage indictor?

Possible Answers:

Correct answer:

Explanation:

Table 1 shows that the indicator does not change much from the pH of vinegar, or 4.5, to the pH of soda pop, 2.5, since it is some shade of pink at all pH values in this range. Thus, the red cabbage indicator could be improved by adding an indicator that changes color drastically in this region. The answer choice that lists the range from 2 to 4 is the closest answer choice.

Example Question #131 : Chemistry

When describing their behavior, gases are typically treated as "ideal gases" in what is known as the ideal gas law. Two science students describe the ideal gas law in their own terms:

Student 1: The ideal gas law is based on the assumptions that a gas consists of a large number of molecules and that gas molecules take up negligible space in a gas due to their minuscule size in comparison to the space between each gas molecule. Also important is the assumption that all of the forces acting on gas molecules are from collisions with other gas molecules or a container and not from anything else. According to the ideal gas law, all gases behave the same so long as those assumptions hold true. Therefore, if you measure the volume of helium gas at a certain temperature and pressure, an equivalent amount of radon gas (a much heavier gas) at the same conditions will have the same volume.

Student 2: The ideal gas law's primary assumption is that a gas consists of a very large number of particles. For example, even within a single bacteria there can be billions of gas molecules despite the bacteria's very small size. Therefore, in a room full of gas, there are so many particles that their random behavior is, on average, uniform. There are exceptions to the ideal gas law and those are gases with very high inter-molecular forces of attraction (IMFAs). A gas with high IMFA will behave very differently than a gas with a low IMFA. As one could imagine, because a gas with a high IMFA will have molecules that tend to attract each other, that gas will display a lower volume than that which would be predicted by the ideal gas law.

"Dipole moment" is a measure of the IMFAs of a molecule. A higher dipole moment indicates stronger interactions. Based on Student 2's description of the ideal gas law, which of the following molecules would display the greatest deviation from ideal behavior when in gaseous form?

Possible Answers:

Ethanol (Dipole moment = 9.7 debye)

Chlorobenzene (Dipole moment = 8.6 debye)

Ethyl ether (Dipole moment = 7.1 debye)

Phenol (Dipole moment = 8.6)

Toluene (Dipole moment = 0.9)

Correct answer:

Ethanol (Dipole moment = 9.7 debye)

Explanation:

The correct answer to this question is the molecule with the highest dipole moment. A higher dipole moment means higher IMFA, which according to Student 2 would cause the greatest deviation from ideal gas behavior.

Example Question #31 : How To Find Synthesis Of Data In Chemistry

Gases can be described by their average molecular speeds. Gases are made up of huge numbers of molecules which vary greatly in speed. The average speeds of those molecules is related to the mass of the gas particles. For example, a heavy gas will have a much lower average molecular speed than a lighter gas. 

The rate of effusion of a gas is defined as the rate at which a gas in a chamber can escape through a pinhole. A gas molecule with a higher average molecular speed is more likely to exit a pinhole and therefore has a higher rate of effusion.

The rate of diffusion of a gas is the rate at which a quantity of gas can spread uniformally throughout a room. Its relationship with the average speed of gas molecules is parallel to that of the rate of effusion. Based on this information and the information provided in the passage, which of the following gases would have the lowest rate of diffusion?

Possible Answers:

Radon (molecular weight = 222 amu)

Hydrogen gas (molecular weight = 2 amu)

Chlorine gas (molecular weight = 71 amu)

Carbon Dioxide (molecular weight = 44 amu)

Oxygen gas (molecular weight = 32 amu)

Correct answer:

Radon (molecular weight = 222 amu)

Explanation:

The correct answer is radon gas. Radon has the largest molecular weight of all the gases presented and therefore would have the lowest average molecular speed. This would indicate also the lowest rate of both effusion and diffusion.

Example Question #31 : How To Find Synthesis Of Data In Chemistry

The electrons of an atom surround the nucleus and reside in atomic orbitals. In transition metals such as iron () and cobalt (), the outermost electrons reside in  orbitals. For a free metal, these  orbitals are equal in energy.  However, as soon as ligands (molecules or ions) bind the metal, the metal  orbitals split in energy (Figure 1).

Screen shot 2015 05 24 at 9.09.43 pm

Scientists perform a number of experiments to determine how various factors affect the magnitude of splitting. They find that the charge on the metal, the metal's position on the periodic table (whether it resides in Period 4, 5, or 6), and the identity of the ligand are all important factors. The scientists' results are summarized in Table 1. Note that a higher value of  indicates larger splitting.

 

Table 1

Screen_shot_2015-05-24_at_9.10.29_pm

Which of the following statements is supported by the data presented in Table 1?

Possible Answers:

 produces a smaller splitting magnitude than .

 produces a larger splitting magnitude than .

 produces a larger splitting magnitude than .

 and  produce roughly the same splitting magnitude.

Correct answer:

 produces a larger splitting magnitude than .

Explanation:

If we compare  and , we see that only the identity of the ligand differs.  produces a much larger splitting magnitude relative to .

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