Question 1

Which statement best describes the Law of Conservation of Matter as it applies to chemical reactions?

Accepted Answer

Atoms are rearranged during a chemical reaction, but the total number of atoms remains the same.

Question 2

Given the balanced reaction: $$2 \mathrm{H}_2 (g) + \mathrm{O}_2 (g) \rightarrow 2 \mathrm{H}_2\mathrm{O} (l)$$, how many moles of water are produced from 4 moles of hydrogen gas?

Accepted Answer

4 moles

Question 3

Which of the following is the correct definition of a reactant in a chemical reaction?

Accepted Answer

A substance that comes together to react.

Question 4

How many molecules are present in 2 moles of a substance?

Accepted Answer

$$1.2044 	imes 10$$^{24}$$

Question 5

Which of the following reactions is a combustion reaction?

Accepted Answer

$$\mathrm{CH}_4 (g) + 2 \mathrm{O}_2 (g) \rightarrow \mathrm{CO}_2 (g) + 2 \mathrm{H}_2\mathrm{O} (l)$$

Question 6

In the reaction $$\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6 (s) + 6 \mathrm{O}_2 (g) \rightarrow 6 \mathrm{CO}_2 (g) + 6 \mathrm{H}_2\mathrm{O} (l)$$, what is the oxidation number change for carbon?

Accepted Answer

Carbon is oxidized from $$0 to$$ $$+4$$

Question 7

Which statement correctly describes an exothermic reaction?

Accepted Answer

The reaction releases heat and has a negative enthalpy ($$\Delta H).$$

Question 8

Which of the following best describes the role of a catalyst in a chemical reaction?

Accepted Answer

A catalyst lowers the activation energy and increases the rate of both forward and reverse reactions.

Question 9

Which of the following factors will increase the rate of a chemical reaction?

Accepted Answer

Adding a catalyst

Question 10

For the reaction $$\mathrm{CH}_4 (g) + 2 \mathrm{O}_2 (g) \rightarrow \mathrm{CO}_2 (g) + 2 \mathrm{H}_2\mathrm{O} (l)$$, which element is reduced?

Accepted Answer

Oxygen

Question 11

Which of the following statements about entropy ($$\Delta S) is $$correct?

Accepted Answer

Entropy is a measure of disorder and increases when a solid melts to a liquid.

Question 12

Which of the following reactions is spontaneous under standard conditions?

Accepted Answer

A reaction with $$\Delta G \u003c 0$$

Question 13

Which of the following is true about redox reactions?

Accepted Answer

Reduction is the gain of electrons.

Question 14

In the reaction $$\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6 (s) + 6 \mathrm{O}_2 (g) \rightarrow 6 \mathrm{CO}_2 (g) + 6 \mathrm{H}_2\mathrm{O} (l)$$, which species is the oxidizing agent?

Accepted Answer

$$\mathrm{O}_2$$

Question 15

Which of the following best describes a coupled reaction in metabolism?

Accepted Answer

A reaction that is linked to another reaction so that the sum of the reactions is exergonic.

Question 16

Which of the following changes will increase the entropy ($$\Delta S) of a $$system?

Accepted Answer

Melting ice to liquid water

Question 17

Which of the following statements about activation energy is correct?

Accepted Answer

A lower activation energy results in a faster reaction rate.

Question 18

Which of the following is true about the enthalpy ($$\Delta H) of a $$reaction?

Accepted Answer

It is the difference between the chemical energy of products and reactants.

Question 19

Which of the following best describes the effect of increasing reactant concentration on reaction rate?

Accepted Answer

It increases the reaction rate by increasing the number of collisions.

Question 20

Which of the following is a correct statement about free energy ($$\Delta G) in $$biochemical reactions?

Accepted Answer

If $$\Delta G is $$negative, the reaction is spontaneous.

GOB Chemistry: Chemical Reactions, Stoichiometry, Thermodynamics, and Kinetics

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