Q: Which of the following is the correct formula to calculate the number of moles from a given mass and molar mass?

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

Q: How many moles of $$\mathrm{CO_2$}$$ are produced from $$0.0679\ \mathrm{g} of $$propane ($$\mathrm{C_3H_8}) in $$excess oxygen? (Molar mass $$= 44.09\ \mathrm{g/mol})$$

$$4.62 \times 10$$^{-3}$$ moles

Q: Which of the following is the correct relationship for calculating the mass percent of an element A in a compound?

$$\dfrac{\text{Mass of A}}{\text{Total mass of compound}} \times 100\%$$

Question 1

Which of the following best describes the purpose of stoichiometric coefficients in a balanced chemical equation?

Accepted Answer

They show the ratio of reactants to products required for the reaction to occur.

Question 2

A student is asked to balance the following equation: $$\mathrm{C_3H_8 + O_2$ \rightarrow CO_2$ + H_2O}. $$What is the correct set of coefficients to balance this equation?

Accepted Answer

$$1, 5, 3, 4$$

Question 3

Which of the following statements about balancing chemical equations is correct?

Accepted Answer

You should only change the coefficients in front of chemical formulas to balance the equation.

Question 4

Calculate the number of molecules in $$26\ \mathrm{g} of $$iodine trifluoride ($$\mathrm{IF_3$}). ($$Molar mass of $$\mathrm{IF_3$} = 183.90\ \mathrm{g/mol})$$

Accepted Answer

$$8.5 	imes 10$$^{22}$$

Question 5

A sample contains $$4.56 	imes 10$$^{22}$$ molecules of water ($$\mathrm{H_2O}$$). How many moles of hydrogen atoms are present?

Accepted Answer

$$0.151$$ moles

Question 6

Which of the following is the correct formula to calculate the number of moles from a given mass and molar mass?

Accepted Answer

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

Question 7

A compound is found to contain $$31.3\%$$ calcium, $$18.8\%$$ carbon, and $$50.0\%$$ oxygen by mass. What is its empirical formula?

Accepted Answer

$$\mathrm{CaC_2O_4}$$

Question 8

Which of the following best defines Avogadro's number?

Accepted Answer

The number of particles in $$1\ \mathrm{mol} of a $$substance.

Question 9

If $$0.200\ \mathrm{g} of$$ $$\mathrm{O_2$} is $$available for the combustion of propane ($$\mathrm{C_3H_8}$$), and $$0.0679\ \mathrm{g} of $$propane is present, which reactant is limiting? (Molar mass: $$\mathrm{O_2$} = 32.00\ \mathrm{g/mol}$$, $$\mathrm{C_3H_8} = 44.09\ \mathrm{g/mol})$$

Accepted Answer

$$\mathrm{O_2$}$$

Question 10

What is the percent yield if the theoretical yield of $$\mathrm{SF_4$} is$$ $$1.29\ \mathrm{g}$$ and the actual yield is $$1.05\ \mathrm{g}$$?

Accepted Answer

$$81.4\%$$

Question 11

Which of the following is the correct molar mass of $$\mathrm{H_2O}$$?

Accepted Answer

$$18.015\ \mathrm{g/mol}$$

Question 12

How many moles of $$\mathrm{CO_2$}$$ are produced from $$0.0679\ \mathrm{g} of $$propane ($$\mathrm{C_3H_8}) in $$excess oxygen? (Molar mass $$= 44.09\ \mathrm{g/mol})$$

Accepted Answer

$$4.62 	imes 10$$^{-3}$$ moles

Question 13

Which of the following is the correct relationship for calculating the mass percent of an element A in a compound?

Accepted Answer

$$\dfrac{	ext{Mass of A}}{	ext{Total mass of compound}} 	imes 100\%$$

Question 14

A reaction has the following balanced equation: $$4\mathrm{NH_3$} + 3\mathrm{O_2$} \rightarrow 2\mathrm{N_2$} + 6\mathrm{H_2O}. $$How many moles of $$\mathrm{O_2$}$$ are required to react completely with $$3.61$$ moles of $$\mathrm{NH_3$}$$?

Accepted Answer

$$2.71$$ moles

Question 15

Which of the following best explains why the atomic mass of an element is not a whole number?

Accepted Answer

It is the weighted average of all naturally occurring isotopes.

Question 16

If $$0.0651$$ moles of $$\mathrm{Fe_2$(SO_4$)_3}$$ are present, how many oxygen atoms are there in the sample?

Accepted Answer

$$4.70 	imes 10$$^{23}$$

Question 17

Which of the following is the correct definition of molar mass?

Accepted Answer

The mass (in grams) of one mole of a substance.

Question 18

A reaction has the following balanced equation: $$3\mathrm{Cu(NO_3$)_2} + 2\mathrm{Na_3PO_4} \rightarrow \mathrm{Cu_3$(PO_4$)_2} + 6\mathrm{$$NaNO_3$$}. $$How many moles of $$\mathrm{$$NaNO_3$$}$$ are produced from $$0.5$$ moles of $$\mathrm{Cu(NO_3$)_2}$$?

Accepted Answer

$$1.0$$ moles

Quantitative Chemistry: Chemical Reactions and Stoichiometry (General Chemistry Study Notes)

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