Q: Which of the following best describes Avogadro’s number?

The number of particles in 1 mole of a substance, $$6.022 \times 10$$^{23}$$.

Q: How many aluminum atoms are in a $$16.2 g $$aluminum can? (Atomic mass of Al = $$26.98 g/$$mol)

$$3.62 \times 10$$^{23}$$ atoms

Q: Which statement about the mole is correct?

A mole contains $$6.022 \times 10$$^{23}$$ particles, regardless of the substance.

Q: Which conversion factor would you use to convert from grams of a compound to moles of a compound?

$$\frac{1\ \text{mol}}{\text{molar mass in g}}$$

Q: Which of the following is the correct formula for calculating percent composition by mass?

$$\text{Percent} = \frac{\text{part}}{\text{whole}} \times 100\%$$

Question 1

Which of the following best describes Avogadro’s number?

Accepted Answer

The number of particles in 1 mole of a substance, $$6.022 	imes 10$$^{23}$$.

Question 2

A sample contains $$1.1 	imes 10$$^{22}$$ silver atoms. How many moles of silver are present?

Accepted Answer

$$1.8 	imes 10$$^{-2}$$ moles

Question 3

What is the molar mass of water ($$H_2O$$)?

Accepted Answer

$$18.02 g/$$mol

Question 4

If you have $$57.8 g of $$sulfur, how many moles of sulfur do you have? (Atomic mass of S = $$32.06 g/$$mol)

Accepted Answer

$$1.80$$ moles

Question 5

How many aluminum atoms are in a $$16.2 g $$aluminum can? (Atomic mass of Al = $$26.98 g/$$mol)

Accepted Answer

$$3.62 	imes 10$$^{23}$$ atoms

Question 6

Which statement about the mole is correct?

Accepted Answer

A mole contains $$6.022 	imes 10$$^{23}$$ particles, regardless of the substance.

Question 7

A hardware store customer buys $$1.18 kg of $$nails. If a dozen nails has a mass of $$0.07 kg$$, how many nails did the customer buy?

Accepted Answer

202 nails

Question 8

Which of the following is the correct empirical formula for glucose ($$C_6H_{12}O_6$)?

Accepted Answer

$$CH_2O$$

Question 9

What is the mass percent of sodium in sodium chloride ($$NaCl) if$$ $$NaCl is$$ $$39\%$$ sodium by mass?

Accepted Answer

$$39\%$$

Question 10

Which conversion factor would you use to convert from grams of a compound to moles of a compound?

Accepted Answer

$$\frac{1\ 	ext{mol}}{	ext{molar mass in g}}$$

Question 11

A compound has a molar mass of $$150.2 g/$$mol and contains $$10$$ moles of carbon per mole of compound. How many grams of carbon are in $$55.4 g of $$the compound? (Atomic mass of C = $$12.01 g/$$mol)

Accepted Answer

$$44.3 g$$

Question 12

Which of the following is NOT a correct use of the mole concept?

Accepted Answer

Measuring the temperature of a substance.

Question 13

If $$1$$ mole of $$CaCO_3$$ contains $$1$$ mole of Ca, $$1$$ mole of C, and $$3$$ moles of O, how many moles of oxygen atoms are present in $$2$$ moles of $$CaCO_3$$?

Accepted Answer

$$6$$ moles

Question 14

Which of the following best explains why the mole is used in chemistry?

Accepted Answer

It allows chemists to count large numbers of particles using mass.

Question 15

A sample of water contains $$2$$ moles of $$H_2O. $$How many moles of hydrogen atoms are present?

Accepted Answer

$$4$$ moles

Question 16

Which of the following is the correct formula for calculating percent composition by mass?

Accepted Answer

$$	ext{Percent} = \frac{	ext{part}}{	ext{whole}} 	imes 100\%$$

Question 17

At standard temperature and pressure (STP), what is the volume occupied by one mole of any gas?

Accepted Answer

$$22.4 L$$

Question 18

Which of the following is true about empirical and molecular formulas?

Accepted Answer

Empirical formulas show the simplest whole-number ratio of atoms in a compound.

Question 19

A chemist needs to find the amount of sodium in sodium chloride for dietary purposes. Which concept is most relevant?

Accepted Answer

Percent composition by mass

Question 20

Which of the following is the correct relationship between atomic mass and molar mass?

Accepted Answer

The molar mass in grams is numerically equal to the atomic mass in amu.

Moles and Chemical Composition: The Mole Concept, Molar Mass, and Chemical Calculations

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