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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