The number of particles in one mole, $6.022 \times 10^{23}$.

$\text{moles} = \dfrac{\text{mass (g)}}{\text{molar mass (g/mol)}}$

Question 1

Which of the following best describes Avogadro's number?

Accepted Answer

The number of particles in one mole, $6.022 	imes 10^{23}$.

Question 2

A sample contains $3.01 	imes 10^{23}$ molecules of oxygen gas ($O_2$). How many moles of $O_2$ are present?

Accepted Answer

$0.50$ moles

Question 3

Which formula is used to convert mass to moles?

Accepted Answer

$	ext{moles} = \dfrac{	ext{mass (g)}}{	ext{molar mass (g/mol)}}$

Question 4

A chemical reaction has a theoretical yield of $10.0$ g and an actual yield of $7.5$ g. What is the percent yield?

Accepted Answer

$75\%$

Question 5

Which of the following is an empirical formula?

Accepted Answer

$CH_2O$

Question 6

A reaction produces $2.0$ moles of $CO_2$ from $1.0$ mole of $C_2H_4$. What is the mole ratio of $CO_2$ to $C_2H_4$?

Accepted Answer

$2:1$

Question 7

Which law states that the volume of a gas is directly proportional to its temperature at constant pressure?

Accepted Answer

Charles's Law

Question 8

If the pressure of a gas is doubled while temperature and amount remain constant, what happens to the volume according to Boyle's Law?

Accepted Answer

Volume is halved.

Question 9

Which equation represents the Ideal Gas Law?

Accepted Answer

$PV = nRT$

Question 10

A $2.0$ L container holds $0.50$ moles of a gas at $300$ K. What is the pressure in atm? ($R = 0.0821$ L·atm/mol·K)

Accepted Answer

$6.16$ atm$

Question 11

Dalton's Law of Partial Pressures is best applied in which scenario?

Accepted Answer

Calculating the total pressure of a mixture of gases in a scuba tank.

Question 12

A gas sample at $1.0$ atm and $273$ K occupies $22.4$ L. If the temperature is increased to $546$ K at constant pressure, what is the new volume?

Accepted Answer

$44.8$ L

Question 13

Which of the following is NOT a property of gases?

Accepted Answer

Definite shape

Question 14

A reaction has a $60\%$ yield. If the theoretical yield is $50$ g, what is the actual yield?

Accepted Answer

$30$ g

Question 15

Which statement about empirical and molecular formulas is correct?

Accepted Answer

The molecular formula is a whole-number multiple of the empirical formula.

Question 16

A mixture contains $2$ atm of $O_2$ and $3$ atm of $N_2$. What is the total pressure according to Dalton's Law?

Accepted Answer

$5$ atm

Question 17

Which gas law explains why a balloon expands when heated?

Accepted Answer

Charles's Law

Question 18

A $5.0$ g sample of $NaCl$ is dissolved in water. What is the number of moles of $NaCl$? ($M_{NaCl} = 58.44$ g/mol)

Accepted Answer

$0.086$ moles

Question 19

Which of the following best describes the relationship in Boyle's Law?

Accepted Answer

$P_1V_1 = P_2V_2$

Study Guide: The Mole Concept, Chemical Equations, and Gases

Study Guide - Practice Questions