Q: A 1.50 mol sample of sodium carbonate ($\mathrm{Na_2CO_3}$) contains how many oxygen atoms?

$1.81 \times 10^{24}$ oxygen atoms

Q: Which of the following reactions is a decomposition reaction?

$2 \mathrm{NaN}_3 (s) \rightarrow 2 \mathrm{Na} (s) + 3 \mathrm{N}_2 (g)$

Q: In a combustion analysis, a 0.255 g sample of an organic compound produces 0.561 g of $\mathrm{CO}_2$ and 0.306 g of $\mathrm{H}_2\mathrm{O}$. What is the first step in determining the empirical formula?

Calculate the moles of carbon from the mass of $\mathrm{CO}_2$ produced.

Q: A strip of zinc metal weighing 2.00 g is placed in an aqueous solution containing 2.50 g of silver nitrate. Which reactant is the limiting reagent in the reaction $\mathrm{Zn} (s) + 2 \mathrm{AgNO}_3 (aq) \rightarrow 2 \mathrm{Ag} (s) + \mathrm{Zn(NO}_3)_2 (aq)$?

Silver nitrate ($\mathrm{AgNO}_3$)

Q: Which of the following best describes a limiting reactant in a chemical reaction?

It is completely consumed and determines the maximum amount of product formed.

Q: Which of the following is the correct sequence of steps to determine an empirical formula from percent composition?

Assume 100 g sample, convert to grams, use molar mass, calculate moles, find mole ratio, write empirical formula.

Q: Which of the following is NOT a correct guideline for balancing chemical equations?

Change the subscripts in chemical formulas to balance atoms.

Question 1

Which of the following statements best describes the law of conservation of mass as illustrated by the reaction $2 \mathrm{H}_2 + \mathrm{O}_2 \rightarrow 2 \mathrm{H}_2\mathrm{O}$?

Accepted Answer

The total number of hydrogen and oxygen atoms is the same before and after the reaction.

Question 2

What is the correct balanced equation for the combustion of ethane ($\mathrm{C}_2\mathrm{H}_6$) in oxygen?

Accepted Answer

$2 \mathrm{C}_2\mathrm{H}_6 + 7 \mathrm{O}_2 \rightarrow 4 \mathrm{CO}_2 + 6 \mathrm{H}_2\mathrm{O}$

Question 3

A sample contains 12 g of $^{12}\mathrm{C}$, 1 mol of $\mathrm{C}_2\mathrm{H}_6$, and $9 	imes 10^{23}$ molecules of $\mathrm{CO}_2$. Arrange these samples in order of increasing number of carbon atoms.

Accepted Answer

12 g of $^{12}\mathrm{C}$ < $9 	imes 10^{23}$ molecules of $\mathrm{CO}_2$ < 1 mol $\mathrm{C}_2\mathrm{H}_6$

Question 4

Which of the following is the correct molar mass of calcium nitrate, $\mathrm{Ca(NO_3)_2}$?

Accepted Answer

$164 \ \mathrm{g/mol}$

Question 5

A 1.50 mol sample of sodium carbonate ($\mathrm{Na_2CO_3}$) contains how many oxygen atoms?

Accepted Answer

$1.81 	imes 10^{24}$ oxygen atoms

Question 6

Which of the following reactions is a decomposition reaction?

Accepted Answer

$2 \mathrm{NaN}_3 (s) \rightarrow 2 \mathrm{Na} (s) + 3 \mathrm{N}_2 (g)$

Question 7

A compound is found to contain 40.00% carbon, 6.71% hydrogen, and 53.29% oxygen by mass. What is the empirical formula?

Accepted Answer

$\mathrm{CH}_2\mathrm{O}$

Question 8

In a combustion analysis, a 0.255 g sample of an organic compound produces 0.561 g of $\mathrm{CO}_2$ and 0.306 g of $\mathrm{H}_2\mathrm{O}$. What is the first step in determining the empirical formula?

Accepted Answer

Calculate the moles of carbon from the mass of $\mathrm{CO}_2$ produced.

Question 9

How many grams of $\mathrm{O}_2$ can be produced from 4.5 g of $\mathrm{KClO}_3$ according to the reaction $2 \mathrm{KClO}_3 \rightarrow 2 \mathrm{KCl} + 3 \mathrm{O}_2$?

Accepted Answer

1.76 g

Question 10

If 1.6 moles of benzene ($\mathrm{C}_6\mathrm{H}_6$) are combusted, how many moles of water are produced according to the equation $2 \mathrm{C}_6\mathrm{H}_6 + 15 \mathrm{O}_2 \rightarrow 12 \mathrm{CO}_2 + 6 \mathrm{H}_2\mathrm{O}$?

Accepted Answer

4.8 moles

Question 11

A strip of zinc metal weighing 2.00 g is placed in an aqueous solution containing 2.50 g of silver nitrate. Which reactant is the limiting reagent in the reaction $\mathrm{Zn} (s) + 2 \mathrm{AgNO}_3 (aq) \rightarrow 2 \mathrm{Ag} (s) + \mathrm{Zn(NO}_3)_2 (aq)$?

Accepted Answer

Silver nitrate ($\mathrm{AgNO}_3$)

Question 12

What is the percent yield if the theoretical yield of a product is 8.52 g but only 6.27 g is obtained in the laboratory?

Accepted Answer

$73.6\%$

Question 13

Which of the following best describes a limiting reactant in a chemical reaction?

Accepted Answer

It is completely consumed and determines the maximum amount of product formed.

Question 14

Which of the following is the correct sequence of steps to determine an empirical formula from percent composition?

Accepted Answer

Assume 100 g sample, convert to grams, use molar mass, calculate moles, find mole ratio, write empirical formula.

Question 15

A reaction between 10 g of Fe and 20 g of $\mathrm{Cl}_2$ produces $\mathrm{FeCl}_3$ according to $2 \mathrm{Fe} + 3 \mathrm{Cl}_2 \rightarrow 2 \mathrm{FeCl}_3$. What is the theoretical yield of $\mathrm{FeCl}_3$ (in grams)? (Fe: 56 g/mol, $\mathrm{Cl}_2$: 71 g/mol, $\mathrm{FeCl}_3$: 162.2 g/mol)

Accepted Answer

22.9 g

Question 16

Which of the following is NOT a correct guideline for balancing chemical equations?

Accepted Answer

Change the subscripts in chemical formulas to balance atoms.

Question 17

Which of the following best describes the information provided by stoichiometric coefficients in a balanced chemical equation?

Accepted Answer

They indicate the relative number of molecules or moles of each reactant and product.

Stoichiometry, Chemical Equations, and Quantitative Analysis in General Chemistry

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