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

$$6.02 \times 10$$^{23}$$ molecules

$$\frac{1 \text{ mole } C_6H_{12}O_6$}{180.16 \text{ g } C_6H_{12}O_6$}$$

$$1.51 \times 10$$^{23}$$ formula units

Question 1

Which of the following best describes a mole in chemistry?

Accepted Answer

A unit that counts 6.02 x $$10^{23}$$ particles (atoms, molecules, or ions).

Question 2

How many atoms are present in 3.0 moles of magnesium (Mg)?

Accepted Answer

$$1.81 	imes 10$$^{24}$$ atoms

Question 3

A sample contains $$1.2 	imes 10$$^{24}$$ atoms of sulfur (S). How many moles of sulfur are present?

Accepted Answer

$$0.50$$ moles

Question 4

What is the molar mass of $$C_2H_6O ($$ethanol)? (Atomic masses: C = 12.01, H = 1.01, O = 16.00)

Accepted Answer

$$46.08 g/$$mol

Question 5

How many moles of hydrogen atoms are in $$0.250$$ moles of $$C_6H_{14}O$$?

Accepted Answer

$$1.75$$ moles

Question 6

Calculate the mass in grams of $$2.5$$ moles of silver (Ag). (Molar mass of Ag = $$107.9 g/$$mol)

Accepted Answer

$$269.75 g$$

Question 7

A chemist needs $$0.75$$ moles of $$NaCl$$ for a reaction. What mass of $$NaCl$$ should be weighed out? (Na = 22.99, Cl = 35.45)

Accepted Answer

$$43.88 g$$

Question 8

How many molecules are present in $$18.0$$ grams of water ($$H_2O$$)? (Molar mass of $$H_2O = 18.02 g/$$mol)

Accepted Answer

$$6.02 	imes 10$$^{23}$$ molecules

Question 9

Which of the following statements about molar mass is correct?

Accepted Answer

Molar mass is the mass of one mole of a substance in grams.

Question 10

A sample of $$CO_2$$ weighs $$44.0$$ grams. How many moles of $$CO_2$$ are present? (C = 12.01, O = 16.00)

Accepted Answer

$$1.00$$ mole

Question 11

How many moles of oxygen atoms are in $$2.0$$ moles of $$H_2SO_4$$?

Accepted Answer

$$8.0$$ moles

Question 12

Which conversion factor would you use to convert from grams of $$C_6H_{12}O_6$ to moles of C_6H$$_{12}$$O_6$$?

Accepted Answer

$$\frac{1 	ext{ mole } C_6H_{12}O_6$}{180.16 	ext{ g } C_6H_{12}O_6$}$$

Question 13

A patient receives an intravenous solution containing $$0.90$$ grams of $$NaCl. $$How many moles of $$NaCl is $$this? (Na = 22.99, Cl = 35.45)

Accepted Answer

$$0.0154$$ moles

Question 14

Which of the following best explains why chemists use the mole as a counting unit?

Accepted Answer

Atoms and molecules are too small to count individually, so the mole allows chemists to work with practical amounts.

Question 15

How many formula units are in $$0.25$$ moles of $$Na_2SO_4$$?

Accepted Answer

$$1.51 	imes 10$$^{23}$$ formula units

Question 16

A chemist has $$59.8$$ grams of water. How many moles of water does she have? (Molar mass of $$H_2O = 18.02 g/$$mol)

Accepted Answer

$$3.32$$ moles

Question 17

Which of the following is the correct molar mass for $$Li_2CO_3$$? (Li = 6.94, C = 12.01, O = 16.00)

Accepted Answer

$$73.89 g/$$mol

Question 18

If you have $$0.50$$ moles of $$C_9H_8O_4 ($$aspirin), how many moles of oxygen atoms are present?

Accepted Answer

$$2.0$$ moles

Question 19

Which of the following is NOT a correct use of Avogadro’s number?

Accepted Answer

To convert between grams and liters of a substance.

The Mole and Calculating Molar Mass: Study Notes for General Chemistry

Study Guide - Practice Questions