Free Practice Quiz Question List

02 The Mole and Chemical Composition Online Quiz Questions

Use this free practice quiz with 20 questions to review 02 The Mole and Chemical Composition, test your knowledge, and prepare for your next test or exam.

20 questions

Choose one

1 point

A sample contains 0.250 mol of CaCl₂ formula units. How many moles of chloride ions does it contain?

A
0.250 mol of chloride ions
B
0.500 mol of chloride ions
C
0.750 mol of chloride ions
D
1.00 mol of chloride ions

Choose one

1 point

A sample contains 0.400 mol of H₂O molecules. What is the total amount, in moles, of all atoms in the sample?

A
0.400 mol of atoms
B
0.800 mol of atoms
C
1.20 mol of atoms
D
2.40 mol of atoms

Choose one

1 point

A 2.50 mol sample of NaCl has a molar mass of 58.44 g/mol. What is its mass to three significant figures?

A
23.4 g
B
58.4 g
C
146 g
D
234 g

Choose one

1 point

Calculate the molar mass of Al₂(SO₄)₃ using Al = 26.98 g/mol, S = 32.06 g/mol, and O = 16.00 g/mol. Give your answer to four significant figures.

A
150.2 g/mol
B
246.1 g/mol
C
342.1 g/mol
D
438.2 g/mol

Choose one

1 point

Using Mg = 24.31 g/mol and O = 16.00 g/mol, what percentage of the mass of MgO is oxygen? Round to three significant figures.

A
28.4%
B
39.7%
C
60.3%
D
65.8%

Choose one

1 point

Percentages calculated from a compound's formula are reported as 24.12% of one element and 75.86% of another. Which conclusion is best supported?

A
The compound must contain an unreported element making up exactly 0.02% of its mass.
B
The percentages are impossible because they must add to exactly 100.00%.
C
The slight shortfall can result from rounding; the unrounded percentages may total 100%.
D
One percentage must be increased by 0.02 percentage points, but the information does not identify which one.

Choose one

1 point

A sample contains 0.200 mol Al and 0.300 mol O. What is the empirical formula?

A
AlO
B
Al₂O₃
C
Al₃O₂
D
AlO₃

Choose one

1 point

Analysis of a compound gives the mole ratio C:H:O = 1.00:1.50:1.00. Which empirical formula represents the simplest whole-number ratio?

A
C₂H₂O₂
B
CH₃O
C
C₂H₃O₂
D
CH₂O₂

Choose one

1 point

A compound is 52.14% C, 13.13% H, and 34.73% O by mass. Using C = 12.01 g/mol, H = 1.008 g/mol, and O = 16.00 g/mol, what is its empirical formula?

A
CH₃O
B
C₂H₆O
C
C₂H₄O₂
D
C₄H₁₂O₂

Choose one

1 point

A compound has empirical formula CH₂O and molar mass 180.16 g/mol. Using C = 12.01 g/mol, H = 1.008 g/mol, and O = 16.00 g/mol, what is its molecular formula?

A
CH₂O
B
C₃H₆O₃
C
C₅H₁₀O₅
D
C₆H₁₂O₆

Choose one

1 point

A compound is reported to have empirical formula CH₂O and molar mass 75.08 g/mol. Using C = 12.01 g/mol, H = 1.008 g/mol, and O = 16.00 g/mol, what can be concluded?

A
The data are inconsistent because the multiplier is not a whole number.
B
The molecular formula is C₂.₅H₅O₂.₅.
C
The molecular formula is C₂H₄O₂ because the ratio should be rounded down.
D
The molecular formula is C₃H₆O₃ because the ratio should be rounded up.

Choose one

1 point

How many moles of atoms in total are present in 1 mol of Al₂(SO₄)₃ formula units?

A
3 mol of atoms
B
12 mol of atoms
C
17 mol of atoms
D
18 mol of atoms

Choose one

1 point

Why does knowing that a compound's empirical formula is CH₂O not, by itself, determine its molecular formula?

A
The empirical formula always is the molecular formula, so no other information is needed.
B
A molecular molar mass or other molecular-size information is needed to determine the integer multiplier.
C
The compound's percent composition alone always gives the molecular formula.
D
The multiplier is determined by the number of elements in the empirical formula.

Choose one

1 point

A sample contains $0.400\ \mathrm{mol}$ of water molecules. Which pair gives the amounts of hydrogen atoms and oxygen atoms in the sample, respectively?

A
$0.800\ \mathrm{mol}$ H atoms and $0.400\ \mathrm{mol}$ O atoms
B
$0.400\ \mathrm{mol}$ H atoms and $0.400\ \mathrm{mol}$ O atoms
C
$0.800\ \mathrm{mol}$ H atoms and $0.800\ \mathrm{mol}$ O atoms
D
$0.400\ \mathrm{mol}$ H atoms and $0.800\ \mathrm{mol}$ O atoms

Choose one

1 point

A compound contains $43.6\%$ phosphorus and $56.4\%$ oxygen by mass. Given molar masses of $30.97\ \mathrm{g/mol}$ for P and $16.00\ \mathrm{g/mol}$ for O, what is its empirical formula?

A
$\mathrm{PO_2}$
B
$\mathrm{P_2O_3}$
C
$\mathrm{P_2O_5}$
D
$\mathrm{P_5O_2}$

Choose one

1 point

Calculate the molar mass of $\mathrm{Ca(OH)_2}$ using $40.08\ \mathrm{g/mol}$ for Ca, $16.00\ \mathrm{g/mol}$ for O, and $1.008\ \mathrm{g/mol}$ for H. Which value is correct to four significant figures?

A
$57.08\ \mathrm{g/mol}$
B
$74.10\ \mathrm{g/mol}$
C
$91.12\ \mathrm{g/mol}$
D
$74.08\ \mathrm{g/mol}$

Choose one

1 point

What mass, to three significant figures, corresponds to $1.75\ \mathrm{mol}$ of NaCl if its molar mass is $58.44\ \mathrm{g/mol}$ ?

A
$102\ \mathrm{g}$
B
$0.0299\ \mathrm{g}$
C
$33.4\ \mathrm{g}$
D
$146\ \mathrm{g}$

Choose one

1 point

Using $12.01\ \mathrm{g/mol}$ for C and $1.008\ \mathrm{g/mol}$ for H, what percentage of the mass of $\mathrm{CH_4}$ is contributed by hydrogen?

A
$6.29\%$
B
$74.87\%$
C
$33.42\%$
D
$25.13\%$

Choose one

1 point

A sample contains $3.00\ \mathrm{g}$ C, $1.00\ \mathrm{g}$ H, and $4.00\ \mathrm{g}$ O. Given molar masses of $12.01\ \mathrm{g/mol}$ for C, $1.008\ \mathrm{g/mol}$ for H, and $16.00\ \mathrm{g/mol}$ for O, what empirical formula best represents the measured composition?

A
$\mathrm{C_3HO_4}$
B
$\mathrm{CH_2O}$
C
$\mathrm{CH_4O}$
D
$\mathrm{C_2H_8O_2}$

Choose one

1 point

An analysis gives the mole ratio $\mathrm{C:H:O}=1:1.50:1$ . Which formula expresses the simplest whole-number ratio of atoms?

A
$\mathrm{CHO}$
B
$\mathrm{C_2H_3O_2}$
C
$\mathrm{C_2H_2O_2}$
D
$\mathrm{C_4H_6O_4}$