Q: Which equation correctly represents the Law of Mass Conservation in a chemical reaction?

$$\text{Number of atoms of each element (reactants)} = \text{Number of atoms of each element (products)}$$

Q: Which of the following is an example of a decomposition reaction?

$$2 \text{HgO}(s) \rightarrow 2 \text{Hg}(l) + \text{O}_2(g)$$

Q: How many atoms of oxygen are in 0.250 mole of aspirin, $$\text{C}_9\text{H}_8\text{O}_4$$?

$$0.250 \text{mol} \times \frac{4 \text{mol O}}{1 \text{mol C}_9\text{H}_8\text{O}_4} = 1.00 \text{mol O}$$

Q: Which conversion factor would you use to convert grams of methane ($$\text{CH}_4) to $$moles?

$$\frac{1 \text{mol CH}_4}{16.0 \text{g CH}_4}$$

Question 1

Which statement best describes the collision theory of chemical reactions?

Accepted Answer

A reaction occurs only when molecules collide with sufficient energy to break bonds in the reactants.

Question 2

In the energy diagram for a chemical reaction, what does the activation energy represent?

Accepted Answer

The minimum energy required for reactants to form products.

Question 3

Which equation correctly represents the Law of Mass Conservation in a chemical reaction?

Accepted Answer

$$	ext{Number of atoms of each element (reactants)} = 	ext{Number of atoms of each element (products)}$$

Question 4

A reaction is described as exothermic. Which of the following is true?

Accepted Answer

The energy of the products is less than the energy of the reactants.

Question 5

Which of the following is an example of a decomposition reaction?

Accepted Answer

$$2 	ext{HgO}(s) ightarrow 2 	ext{Hg}(l) + 	ext{O}_2(g)$$

Question 6

Which of the following best describes a single replacement reaction?

Accepted Answer

One element replaces another element in a compound.

Question 7

If you change the subscript in a chemical formula, what law are you violating?

Accepted Answer

Law of Constant Composition

Question 8

How many atoms of oxygen are in 0.250 mole of aspirin, $$	ext{C}_9	ext{H}_8	ext{O}_4$$?

Accepted Answer

$$0.250 	ext{mol} 	imes \frac{4 	ext{mol O}}{1 	ext{mol C}_9	ext{H}_8	ext{O}_4} = 1.00 	ext{mol O}$$

Question 9

What is the molar mass of $$	ext{K}_2	ext{O}$$? (Express your answer to four significant figures.)

Accepted Answer

94.20 g/mol

Question 10

Which conversion factor would you use to convert grams of methane ($$	ext{CH}_4) to $$moles?

Accepted Answer

$$\frac{1 	ext{mol CH}_4}{16.0 	ext{g CH}_4}$$

Question 11

A sample of helium gas in a balloon has a volume of 6.4 L at a pressure of 0.70 atm. If the pressure is increased to 1.40 atm (temperature constant), what is the new volume?

Accepted Answer

3.2 L

Question 12

Which equation represents Boyle’s Law?

Accepted Answer

$$P_1$$ $$V_1$$ = $$P_2$$ $$V_2$$

Question 13

Which property of gases explains why they are compressible?

Accepted Answer

Gas particles are far apart and have small volumes compared to the container.

Question 14

At STP, what is the molar volume of any ideal gas?

Accepted Answer

22.4 L

Question 15

Dalton’s Law of Partial Pressures states:

Accepted Answer

$$P_T = P_1$ + P_2$ + P_3$ + \ldots$$

Question 16

A scuba tank contains O2 with a pressure of 0.450 atm and He at 855 mmHg. What is the total pressure in mmHg?

Accepted Answer

1197 mmHg

Question 17

Which of the following is true about oxidation-reduction (redox) reactions?

Accepted Answer

Oxidation is the loss of electrons, and reduction is the gain of electrons.

Question 18

If 25.0 g of ethane gas ($$	ext{C}_2	ext{H}_6) $$burn in oxygen, how many grams of $$	ext{CO}_2$$ are produced? (Use molar masses: $$	ext{C}_2	ext{H}_6 = 30.07 g/$$mol, $$	ext{CO}_2 = 44.01 g/$$mol)

Accepted Answer

73.2 g

Chemical Reactions, Chemical Quantities, and Gases: Study Guide

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