Q: Which of the following statements about the mole is correct?

One mole of any substance contains $$6.022 \times 10$$^{23}$$ particles.

Question 1

Which of the following best describes the relationship between the mole concept and measuring the quantity of a sample of matter in the chemistry lab?

Accepted Answer

The mole concept allows chemists to relate the mass of a substance to the number of particles it contains.

Question 2

A student measures out 18.0 g of water ($$H_2O) in $$the lab. What is the number of moles of water in the sample? (Molar mass of $$H_2O = 18.0 \ g/mol)$$

Accepted Answer

$$1.0 \ mol$$

Question 3

Which equation correctly relates the mass ($$m$$), molar mass ($$M$$), and number of moles ($$n) of a $$substance?

Accepted Answer

$$n = \frac{m}{M}$$

Question 4

You are given a sample of sodium chloride ($$NaCl) $$with a mass of 58.5 g. What is the number of moles in the sample? (Molar mass of $$NaCl = 58.5 \ g/mol)$$

Accepted Answer

$$1.0 \ mol$$

Question 5

Which of the following is the correct way to calculate the molar mass of $$CO_2$$ from its formula?

Accepted Answer

Add the atomic masses of 1 carbon atom and 2 oxygen atoms: $$12.0 \ g/mol + 2 	imes 16.0 \ g/mol = 44.0 \ g/mol$$

Question 6

A chemist needs 0.25 moles of glucose ($$C_6H_{12}O_6$) for an experiment. What mass of glucose should be weighed out? (Molar mass of C_6H$$_{12}$$O_6 = 180$$ \ g/mol$$)

Accepted Answer

$$45 \ g$$

Question 7

Why is it important to use the mole concept when preparing solutions in the laboratory?

Accepted Answer

It ensures the correct number of particles are present for reactions to occur as expected.

Question 8

Which of the following best explains why the molar mass of a compound is calculated from its chemical formula?

Accepted Answer

The chemical formula shows the number and type of atoms in one molecule, allowing calculation of total mass per mole.

Question 9

A student is given 24.0 g of magnesium ($$Mg). $$How many moles of magnesium does the student have? (Molar mass of $$Mg = 24.3 \ g/mol)$$

Accepted Answer

$$0.99 \ mol$$

Question 10

If you have 2.0 moles of $$Na_2SO_4$$, what is the total mass of the sample? (Molar mass of $$Na_2SO_4 = 142 \ g/mol)$$

Accepted Answer

$$284 \ g$$

Question 11

A laboratory technician needs to prepare 0.50 moles of $$KCl$$ for a medical solution. What mass of $$KCl$$ should be used? (Molar mass of $$KCl = 74.5 \ g/mol)$$

Accepted Answer

$$37.25 \ g$$

Question 12

Which of the following statements about the mole is correct?

Accepted Answer

One mole of any substance contains $$6.022 	imes 10$$^{23}$$ particles.

Question 13

A sample contains 0.75 moles of $$CaCO_3. $$What is the mass of the sample? (Molar mass of $$CaCO_3 = 100$$ \ g/mol$$)

Accepted Answer

$$75 \ g$$

Question 14

Which calculation would you use to determine the number of moles in a 10.0 g sample of $$NH_3$$? (Molar mass of $$NH_3 = 17.0$$ \ g/mol$$)

Accepted Answer

$$n = \frac{10.0}{17.0}$$

Question 15

A chemist needs to prepare 0.10 moles of $$H_2SO_4$$ for a titration. What mass of $$H_2SO_4 is $$required? (Molar mass of $$H_2SO_4 = 98.0 \ g/mol)$$

Accepted Answer

$$9.8 \ g$$

The Mole Concept and Molar Mass in Chemistry

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