Q: Which of the following best describes Avogadro's number?

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

Q: Which formula is used to convert mass to moles?

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

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

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