Q: A cold medicine tablet contains 30.0 mg of pseudoephedrine hydrochloride (molar mass = $$201.70 g/$$mol). How many molecules of pseudoephedrine hydrochloride are in the tablet?

$$8.95 \times 10$$^{19}$$ molecules

Q: Which of the following is the correct formula for calculating percent yield?

$$\frac{\text{Actual Yield}}{\text{Theoretical Yield}} \times 100$$

Question 1

Which of the following statements best describes Avogadro’s number?

Accepted Answer

It is the number of molecules in 1 mole of a substance, approximately $$6.02 	imes 10$$^{23}$$.

Question 2

A cold medicine tablet contains 30.0 mg of pseudoephedrine hydrochloride (molar mass = $$201.70 g/$$mol). How many molecules of pseudoephedrine hydrochloride are in the tablet?

Accepted Answer

$$8.95 	imes 10$$^{19}$$ molecules

Question 3

Which of the following is the correct sequence of steps for solving a mass-to-mass stoichiometry problem?

Accepted Answer

Write the balanced equation, convert mass to moles, use mole ratio, convert moles to mass.

Question 4

Ibuprofen has a molecular weight of $$206.3 g/$$mol. If a bottle contains $$0.082$$ mol of ibuprofen, what is the mass of ibuprofen in the bottle?

Accepted Answer

$$16.9 g$$

Question 5

A sample contains $$1.00 	imes 10$$^{18}$$ atoms of carbon. What is the mass of this sample? (Atomic weight of carbon = 12.01$ g/mol)

Accepted Answer

$$1.99 	imes 10$$^{-6}$$ g

Question 6

In the reaction $$4Fe + 3O_2 \rightarrow 2Fe_2O_3$$, what is the mole ratio of $$Fe to$$ $$Fe_2O_3$$?

Accepted Answer

$$4:2$$

Question 7

If $$6.2$$ mol of iron reacts completely with oxygen to form iron(III) oxide ($$Fe_2O_3$$), how many moles of $$Fe_2O_3$$ are produced? (Reaction: $$4Fe + 3O_2 \rightarrow 2Fe_2O_3)$$

Accepted Answer

$$3.1$$ mol

Question 8

A reaction produces $$0.022 g of $$calcium oxalate ($$CaC_2O_4$$, molar mass $$128.1 g/$$mol). What mass of calcium chloride ($$CaCl_2$$, molar mass $$111.0 g/$$mol) was used, assuming a 1:1 mole ratio?

Accepted Answer

$$0.019 g$$

Question 9

Which of the following best defines the limiting reagent in a chemical reaction?

Accepted Answer

The reactant that is completely consumed first, thus limiting the amount of product formed.

Question 10

A reaction has a theoretical yield of $$88.0 g of$$ $$CO_2$$, but only $$72.4 g is $$actually produced. What is the percent yield?

Accepted Answer

$$82.3\%$$

Question 11

A chemist reacts $$2350 g of $$boric oxide ($$B_2O_3$$, molar mass $$69.6 g/$$mol) with $$3580 g of $$magnesium (molar mass $$24.3 g/$$mol) to produce boron. If the balanced equation is $$B_2O_3 + 3Mg \rightarrow 2B + 3MgO$$, what is the theoretical yield of boron in grams?

Accepted Answer

$$729 g$$

Question 12

Ethylene ($$C_2H_4) $$reacts with water to form ethyl alcohol ($$C_2H_5OH) $$with a $$78.5\%$$ actual yield. If $$25.0 g of $$ethylene is used (molar mass $$28.0 g/$$mol), how many grams of ethyl alcohol (molar mass $$46.0 g/$$mol) are actually produced?

Accepted Answer

$$32.4 g$$

Question 13

Which of the following is NOT true about the coefficients in a balanced chemical equation?

Accepted Answer

They represent the mass ratios of reactants and products.

Question 14

A solution contains $$3.8 g of $$sodium hydrogen phosphate ($$Na_2HPO_4$$, molar mass $$142.0 g/$$mol). How many moles of $$Na^+$$ ions are present in this dose?

Accepted Answer

$$0.054$$ mol

Question 15

In the reaction $$2NO_2 + H_2O \rightarrow 2HNO_3 + NO$$, how many grams of $$HNO_3 ($$molar mass $$63.0 g/$$mol) are produced from $$1.0$$ mol of $$NO_2$$?

Accepted Answer

$$31.5 g$$

Question 16

Which of the following best describes the relationship between molar mass and molecular weight?

Accepted Answer

Molar mass is the mass in grams of 1 mole of a substance and is numerically equal to its molecular weight in amu.

Question 17

A student is given $$10.0 g of$$ $$NaCl ($$molar mass $$58.44 g/$$mol). How many moles of $$NaCl$$ does this sample contain?

Accepted Answer

$$0.171$$ mol

Question 18

Which of the following is the correct formula for calculating percent yield?

Accepted Answer

$$\frac{	ext{Actual Yield}}{	ext{Theoretical Yield}} 	imes 100$$

Chemical Reactions: Mole and Mass Relationships (Chapter 6 Study Notes)

Study Guide - Practice Questions

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