Q: Which of the following best describes the relationship between the number of moles and the number of atoms in a sample?

The number of atoms $= \text{number of moles} \times 6.022 \times 10^{23}$

Q: Which calculation would you use to determine the number of moles of hydrogen atoms in $15.0\ \mathrm{g}$ of dipyrithione?

$\left( \frac{15.0}{284.38} \right) \times 8$

Question 1

What is the molecular formula of dipyrithione, the active ingredient in some dandruff shampoos?

Accepted Answer

$\mathrm{C_{10}H_8N_2O_2S_2}$

Question 2

Calculate the molar mass of dipyrithione ($\mathrm{C_{10}H_8N_2O_2S_2}$). Use the following atomic masses: C = 12.01 g/mol, H = 1.01 g/mol, N = 14.01 g/mol, O = 16.00 g/mol, S = 32.07 g/mol.

Accepted Answer

$284.38\ \mathrm{g/mol}$

Question 3

How many moles of dipyrithione are present in $25.0\ \mathrm{g}$ of the compound? (Molar mass = $284.38\ \mathrm{g/mol}$)

Accepted Answer

$0.0879\ \mathrm{mol}$

Question 4

How many moles of carbon atoms are present in $25.0\ \mathrm{g}$ of dipyrithione ($\mathrm{C_{10}H_8N_2O_2S_2}$)?

Accepted Answer

$0.879\ \mathrm{mol}$

Question 5

How many moles of dipyrithione contain $8.2 	imes 10^{24}$ atoms of nitrogen? (Avogadro's number $= 6.022 	imes 10^{23}$)

Accepted Answer

$6.8\ \mathrm{mol}$

Question 6

A patient accidentally ingests $10.0\ \mathrm{g}$ of dipyrithione. How many moles of the compound did they ingest? (Molar mass = $284.38\ \mathrm{g/mol}$)

Accepted Answer

$0.0352\ \mathrm{mol}$

Question 7

If a shampoo contains $0.50\ \mathrm{g}$ of dipyrithione per $100\ \mathrm{mL}$, how many moles of dipyrithione are in a $250\ \mathrm{mL}$ bottle?

Accepted Answer

$0.0044\ \mathrm{mol}$

Question 8

Which of the following best describes the relationship between the number of moles and the number of atoms in a sample?

Accepted Answer

The number of atoms $= 	ext{number of moles} 	imes 6.022 	imes 10^{23}$

Question 9

A chemist needs $0.0500\ \mathrm{mol}$ of dipyrithione for an experiment. What mass of dipyrithione should they weigh out? (Molar mass = $284.38\ \mathrm{g/mol}$)

Accepted Answer

$14.2\ \mathrm{g}$

Question 10

If a sample contains $0.100\ \mathrm{mol}$ of dipyrithione, how many molecules of dipyrithione are present?

Accepted Answer

$6.02 	imes 10^{22}$

Question 11

A laboratory technician needs $1.50 	imes 10^{24}$ molecules of dipyrithione for a test. What mass of dipyrithione should be used? (Molar mass = $284.38\ \mathrm{g/mol}$, Avogadro's number $= 6.022 	imes 10^{23}$)

Accepted Answer

$7.09\ \mathrm{g}$

Question 12

Which of the following statements about the composition of dipyrithione is correct?

Accepted Answer

Each molecule contains 2 nitrogen atoms and 2 sulfur atoms.

Question 13

If a shampoo contains $0.25\ \mathrm{g}$ of dipyrithione per $50\ \mathrm{mL}$, how many molecules of dipyrithione are in a $200\ \mathrm{mL}$ bottle? (Molar mass = $284.38\ \mathrm{g/mol}$, Avogadro's number $= 6.022 	imes 10^{23}$)

Accepted Answer

$1.06 	imes 10^{22}$

Question 14

A sample of dipyrithione contains $0.200\ \mathrm{mol}$ of the compound. How many moles of sulfur atoms are present?

Accepted Answer

$0.400\ \mathrm{mol}$

Question 15

Which calculation would you use to determine the number of moles of hydrogen atoms in $15.0\ \mathrm{g}$ of dipyrithione?

Accepted Answer

$\left( \frac{15.0}{284.38} ight) 	imes 8$

Molar Mass, Mole Calculations, and Chemical Composition: Applications in GOB Chemistry

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