Q: How many molecules are present in 10.0 g of aspirin ($$\mathrm{C_9H_8O_4}$$, molar mass = $$180.16\ \mathrm{g/mol}$$)?

$$3.34 \times 10$$^{22}$$ molecules

Q: A tablet contains 30.0 mg of pseudoephedrine hydrochloride ($$\mathrm{C$$_{10}$$H_{16}$$ClNO}$$, molar mass = 201.7$$\ \mathrm{g/mol}$). How many molecules of pseudoephedrine hydrochloride are in the tablet?

$$8.96 \times 10$$^{19}$$ molecules

Q: Which of the following equations correctly expresses percent yield?

$$\text{Percent yield} = \dfrac{\text{Actual yield}}{\text{Theoretical yield}} \times 100$$

Question 1

Which of the following best describes the mole concept in chemistry?

Accepted Answer

A mole is the amount of a substance that contains 6.022 × $$10^{23}$$ particles.

Question 2

Calculate the molar mass of aluminum sulfate, $$\mathrm{Al_2$(SO_4$)_3}.$$

Accepted Answer

$$342.17\ \mathrm{g/mol}$$

Question 3

How many molecules are present in 10.0 g of aspirin ($$\mathrm{C_9H_8O_4}$$, molar mass = $$180.16\ \mathrm{g/mol}$$)?

Accepted Answer

$$3.34 	imes 10$$^{22}$$ molecules

Question 4

Which of the following is the correct mole ratio for the reaction $$3\ \mathrm{H_2$} + \mathrm{N_2$} \rightarrow 2\ \mathrm{NH_3$}$$?

Accepted Answer

$$\dfrac{3\ \mathrm{mol}\ \mathrm{H_2$}}{1\ \mathrm{mol}\ \mathrm{N_2$}}$$

Question 5

A tablet contains 30.0 mg of pseudoephedrine hydrochloride ($$\mathrm{C$$_{10}$$H_{16}$$ClNO}$$, molar mass = 201.7$$\ \mathrm{g/mol}$). How many molecules of pseudoephedrine hydrochloride are in the tablet?

Accepted Answer

$$8.96 	imes 10$$^{19}$$ molecules

Question 6

If 0.082 mol of ibuprofen ($$\mathrm{C$$_{13}$$H_{18}O_2$}$$, molar mass = $$206.3\ \mathrm{g/mol}) is $$present in a bottle, what is the mass of ibuprofen in the bottle?

Accepted Answer

$$16.9\ \mathrm{g}$$

Question 7

How many moles of $$\mathrm{Na_2HPO_4} ($$molar mass = $$142.0\ \mathrm{g/mol}) $$are in a 3.8 g dose?

Accepted Answer

$$0.0268$$ mol

Question 8

In the reaction $$3\ \mathrm{NO_2$} (g) + \mathrm{H_2O} (l) \rightarrow 2\ \mathrm{$$HNO_3$$} (aq) + \mathrm{NO} (g)$$, how many grams of $$\mathrm{$$HNO_3$$} ($$molar mass = $$63.00\ \mathrm{g/mol}) $$are produced from 5.0 g of $$\mathrm{NO_2$} ($$molar mass = $$46.01\ \mathrm{g/mol}$$)?

Accepted Answer

$$4.57\ \mathrm{g}$$

Question 9

Which reactant is the limiting reagent when 25.0 g of nitrogen reacts with 5.00 g of hydrogen to produce ammonia ($$\mathrm{NH_3$}$$)?

Accepted Answer

Hydrogen

Question 10

The combustion of acetylene gas ($$\mathrm{C_2H_2}) $$produces $$88.0\ \mathrm{g} of$$ $$\mathrm{CO_2$} as $$the theoretical yield. If the actual yield is $$72.4\ \mathrm{g}$$, what is the percent yield?

Accepted Answer

$$82.3\%$$

Question 11

Which of the following equations correctly expresses percent yield?

Accepted Answer

$$	ext{Percent yield} = \dfrac{	ext{Actual yield}}{	ext{Theoretical yield}} 	imes 100$$

Question 12

A reaction produces 9.55 g of methanol ($$\mathrm{CH_3OH}) $$from 10.0 g of CO. If the theoretical yield is 11.4 g, what is the percent yield?

Accepted Answer

$$83.8\%$$

Question 13

Which of the following statements about limiting reagents is correct?

Accepted Answer

The limiting reagent is the reactant that is completely consumed first in a chemical reaction.

Question 14

How many moles of hydrogen atoms are present in 3.45 g of pseudoephedrine hydrochloride ($$\mathrm{C$$_{10}$$H_{16}$$ClNO}$$, molar mass = 201.7$$\ \mathrm{g/mol}$)?

Accepted Answer

$$0.274$$ mol

Question 15

Which conversion must be performed first when converting from grams of a compound to the number of molecules?

Accepted Answer

Convert grams to moles using molar mass.

Question 16

In the reaction $$4\ \mathrm{HF} (g) + \mathrm{$$SiO_2$$} (s) \rightarrow \mathrm{$$SiF_4$$} (g) + 2\ \mathrm{H_2O} (l)$$, how many moles of HF are required to react completely with 9.90 mol of $$\mathrm{$$SiO_2$$}$$?

Accepted Answer

$$39.6$$ mol

Question 17

A pizza recipe requires 1 crust, 5 oz tomato sauce, and 2 cups of cheese to make 1 pizza. If you have 4 crusts, 10 cups of cheese, and 15 oz of tomato sauce, how many pizzas can you make and which ingredient is limiting?

Accepted Answer

3 pizzas; tomato sauce is limiting

Chemical Reactions: Mole and Mass Relationships (Stoichiometry)

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