Question 1

Which of the following best describes the greenhouse effect as it relates to Earth's climate?

Accepted Answer

Greenhouse gases allow sunlight to enter the atmosphere, warm Earth's surface, and trap some of the heat radiated from the surface.

Question 2

Which of the following is a chemical change?

Accepted Answer

Rusting of an iron nail.

Question 3

Given the reaction $$2 \mathrm{Mg} (s) + \mathrm{O}_2 (g) \rightarrow 2 \mathrm{MgO} (s)$$, if you start with 42.5 g of Mg and 33.8 g of O$$_2$$, which is the limiting reactant? (Molar masses: Mg = 24.31 g/mol, O$$_2 = 32.00 g/$$mol)

Accepted Answer

Mg

Question 4

Which of the following equations is balanced?

Accepted Answer

$$\mathrm{H}_2\mathrm{SO}_4 + 2\mathrm{NaOH} \rightarrow \mathrm{Na}_2\mathrm{SO}_4 + 2\mathrm{H}_2\mathrm{O}$$

Question 5

During photosynthesis, plants convert CO$$_2$$ and H$$_2O $$into glucose ($$\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6) $$according to the equation: $$6\mathrm{CO}_2 + 6\mathrm{H}_2\mathrm{O} \rightarrow \mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6 + 6\mathrm{O}_2. If a $$plant consumes 37.8 g of CO$$_2$$, what mass of glucose (in grams) can be synthesized? (Molar masses: CO$$_2 = 44.01 g/$$mol, $$\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6 = 180.2 g/$$mol)

Accepted Answer

25.8 g

Question 6

Which of the following is a physical property?

Accepted Answer

Melting point

Question 7

What is the theoretical yield of MgO (in grams) when 42.5 g of Mg reacts with excess O$$_2$$? (Molar mass Mg = 24.31 g/mol, MgO = 40.31 g/mol)

Accepted Answer

70.5 g

Question 8

Which of the following best describes a limiting reactant in a chemical reaction?

Accepted Answer

The reactant that determines the amount of product formed.

Question 9

If the actual yield of MgO in a reaction is 55.9 g, but the theoretical yield is 70.5 g, what is the percent yield?

Accepted Answer

$$79.3\%$$

Question 10

Which of the following is a correct statement about the law of conservation of mass as it applies to chemical reactions?

Accepted Answer

The total mass of reactants equals the total mass of products.

Question 11

Which of the following best describes the reaction of sodium with water?

Accepted Answer

It produces sodium hydroxide and hydrogen gas, and is highly exothermic.

Question 12

Which of the following is the correct balanced equation for the combustion of methane?

Accepted Answer

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

Question 13

Which of the following is NOT a greenhouse gas?

Accepted Answer

N$$_2$$

Question 14

What is the correct sequence of steps for balancing a chemical equation?

Accepted Answer

Write correct formulas, add coefficients to balance atoms, check, and reduce coefficients to lowest whole numbers.

Question 15

Which of the following best describes a chemical property?

Accepted Answer

Flammability

Question 16

Which of the following statements about the reaction $$2\mathrm{C}_8\mathrm{H}_{18} (l) + 25\mathrm{O}_2 (g) \rightarrow 16\mathrm{CO}_2 (g) + 18\mathrm{H}_2\mathrm{O} (g) is $$correct?

Accepted Answer

16 moles of CO$$_2$$ are produced for every 2 moles of octane combusted.

Question 17

Which of the following is a correct description of a physical change?

Accepted Answer

A change that alters only the state or appearance, not the composition.

Question 18

Which of the following best explains why the concentration of CO$$_2 in $$the atmosphere is increasing rapidly since the 20th century?

Accepted Answer

Human activities such as burning fossil fuels are the primary cause.

Chemical Reactions and Chemical Quantities: Study Notes

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