Q: Calculate the molar mass of dipyrithione ($$C_{10}H_8N_2O_2S_2$). Use the following atomic masses: C = 12.01 g/mol, H = 1.008 g/mol, N = 14.01 g/mol, O = 16.00 g/mol, S = 32.07 g/mol.

$$10 \times 12.01 + 8 \times 1.008 + 2 \times 14.01 + 2 \times 16.00 + 2 \times 32.07 = 280.24 g/$$mol

Q: How many moles of carbon atoms are present in 25.0 g of dipyrithione ($$C_{10}H_8N_2O_2S_2$)? (Molar mass = 280.24 g/mol)

$$0.0892 \text{ mol dipyrithione} \times 10 = 0.892$$ mol C

Q: How many moles of dipyrithione contain $$8.2 \times 10$$^{24}$$ atoms of nitrogen? (Each molecule contains 2 N atoms)

$$\frac{8.2 \times 10$$^{24}$$}{2 \times 6.022 \times 10$$^{23}$$} = 6.8$$ mol

Q: If a shampoo contains $$1.50 \times 10$$^{22}$$ molecules of dipyrithione, how many moles of dipyrithione does this represent?

$$\frac{1.50 \times 10$$^{22}$$}{6.022 \times 10$$^{23}$$} = 0.0249$$ mol

Q: A sample contains 0.0500 mol of dipyrithione. How many molecules are present?

$$0.0500 \times 6.022 \times 10$$^{23}$$ = 3.01 \times 10$$^{22}$$ molecules

Q: If you have 0.0357 mol of dipyrithione, how many atoms of sulfur are present? (Each molecule contains 2 S atoms)

$$0.0357 \text{ mol} \times 2 \times 6.022 \times 10$$^{23}$$ = 4.30 \times 10$$^{22}$$ atoms S

Q: Which calculation would you use to determine the number of moles of oxygen atoms in 25.0 g of dipyrithione ($$C_{10}H_8N_2O_2S_2$)?

$$\frac{25.0}{280.24} \times 2$$

Question 1

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

Accepted Answer

C10H8N2O2S2

Question 2

Calculate the molar mass of dipyrithione ($$C_{10}H_8N_2O_2S_2$). Use the following atomic masses: C = 12.01 g/mol, H = 1.008 g/mol, N = 14.01 g/mol, O = 16.00 g/mol, S = 32.07 g/mol.

Accepted Answer

$$10 	imes 12.01 + 8 	imes 1.008 + 2 	imes 14.01 + 2 	imes 16.00 + 2 	imes 32.07 = 280.24 g/$$mol

Question 3

How many moles of dipyrithione are present in 25.0 g of the compound? (Molar mass = 280.24 g/mol)

Accepted Answer

$$\frac{25.0}{280.24} = 0.0892$$ mol

Question 4

How many moles of carbon atoms are present in 25.0 g of dipyrithione ($$C_{10}H_8N_2O_2S_2$)? (Molar mass = 280.24 g/mol)

Accepted Answer

$$0.0892 	ext{ mol dipyrithione} 	imes 10 = 0.892$$ mol C

Question 5

How many moles of dipyrithione contain $$8.2 	imes 10$$^{24}$$ atoms of nitrogen? (Each molecule contains 2 N atoms)

Accepted Answer

$$\frac{8.2 	imes 10$$^{24}$$}{2 	imes 6.022 	imes 10$$^{23}$$} = 6.8$$ mol

Question 6

A shampoo contains 10.0 g of dipyrithione. How many moles of dipyrithione are present? (Molar mass = 280.24 g/mol)

Accepted Answer

$$\frac{10.0}{280.24} = 0.0357$$ mol

Question 7

If a shampoo contains $$1.50 	imes 10$$^{22}$$ molecules of dipyrithione, how many moles of dipyrithione does this represent?

Accepted Answer

$$\frac{1.50 	imes 10$$^{22}$$}{6.022 	imes 10$$^{23}$$} = 0.0249$$ mol

Question 8

Which of the following best describes the role of dipyrithione in dandruff shampoo?

Accepted Answer

It acts as an antibacterial and antifungal agent.

Question 9

A sample contains 0.0500 mol of dipyrithione. How many molecules are present?

Accepted Answer

$$0.0500 	imes 6.022 	imes 10$$^{23}$$ = 3.01 	imes 10$$^{22}$$ molecules

Question 10

If you have 0.0357 mol of dipyrithione, how many atoms of sulfur are present? (Each molecule contains 2 S atoms)

Accepted Answer

$$0.0357 	ext{ mol} 	imes 2 	imes 6.022 	imes 10$$^{23}$$ = 4.30 	imes 10$$^{22}$$ atoms S

Question 11

Which calculation would you use to determine the number of moles of oxygen atoms in 25.0 g of dipyrithione ($$C_{10}H_8N_2O_2S_2$)?

Accepted Answer

$$\frac{25.0}{280.24} 	imes 2$$

Question 12

A shampoo contains 0.0892 mol of dipyrithione. How many atoms of nitrogen are present?

Accepted Answer

$$0.0892 	ext{ mol} 	imes 2 	imes 6.022 	imes 10$$^{23}$$ = 1.07 	imes 10$$^{23}$$ atoms N

Question 13

Which of the following is the correct formula to calculate the number of moles from mass and molar mass?

Accepted Answer

$$	ext{moles} = \frac{	ext{mass (g)}}{	ext{molar mass (g/mol)}}$$

Question 14

If a shampoo contains 0.0500 mol of dipyrithione, how many moles of hydrogen atoms are present?

Accepted Answer

$$0.0500 	imes 8 = 0.400$$ mol H

Question 15

A shampoo contains 25.0 g of dipyrithione. How many molecules of dipyrithione are present? (Molar mass = 280.24 g/mol)

Accepted Answer

$$\frac{25.0}{280.24} 	imes 6.022 	imes 10$$^{23}$$ = 5.37 	imes 10$$^{22}$$ molecules

Question 16

Which of the following statements about molar mass is correct?

Accepted Answer

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

Molecular Formulas, Molar Mass, and Mole Calculations in GOB Chemistry

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