Q: A mining company extracts 2.50 kg of iron ore that is 60.0% pure Fe2O3 by mass. How many grams of iron (Fe) are present in the ore? (Molar mass: Fe2O3 = 159.7 g/mol, Fe = 55.85 g/mol)

$$\displaystyle 839\ \text{g}$$

Q: A can of Freon-12 (CCl2F2) contains 250 g of the compound. What is the mass of chlorine in the can? (Molar mass: CCl2F2 = 120.91 g/mol, Cl = 35.45 g/mol)

$$\displaystyle 146.8\ \text{g}$$

Q: A customer buys 3.4 lbs of medium-sized nails. If a dozen of these nails weighs 0.150 lb, how many nails did the customer buy?

$$\displaystyle 272\ \text{nails}$$

Q: How many atoms are present in 3.5 mol of helium?

$$\displaystyle 2.1 \times 10$$^{24}$$\ \text{atoms}$$

Q: A sample contains $$1.1 \times 10$$^{22}$$ silver atoms. How many moles of silver are present?

$$\displaystyle 1.8 \times 10$$^{-2}$$\ \text{mol}$$

Q: How many moles of sulfur are present in 57.8 g of sulfur? (Molar mass of S = 32.07 g/mol)

$$\displaystyle 1.80\ \text{mol}$$

Q: A typical aluminum can has a mass of 16.2 g. How many aluminum atoms does it contain? (Molar mass of Al = 26.98 g/mol)

$$\displaystyle 3.62 \times 10$$^{23}$$\ \text{atoms}$$

Q: What is the molar mass of carbon dioxide ($$\mathrm{CO_2$}$$)? (Atomic masses: C = 12.01 amu, O = 16.00 amu)

$$\displaystyle 44.01\ \text{g/mol}$$

Q: Calculate the mass in grams of 1.75 mol of water ($$\mathrm{H_2O}). ($$Molar mass of $$\mathrm{H_2O} = 18.02 g/$$mol)

$$\displaystyle 31.5\ \text{g}$$

Question 1

A mining company extracts 2.50 kg of iron ore that is 60.0% pure Fe2O3 by mass. How many grams of iron (Fe) are present in the ore? (Molar mass: Fe2O3 = 159.7 g/mol, Fe = 55.85 g/mol)

Accepted Answer

$$\displaystyle 839\ 	ext{g}$$

Question 2

A can of Freon-12 (CCl2F2) contains 250 g of the compound. What is the mass of chlorine in the can? (Molar mass: CCl2F2 = 120.91 g/mol, Cl = 35.45 g/mol)

Accepted Answer

$$\displaystyle 146.8\ 	ext{g}$$

Question 3

A customer buys 3.4 lbs of medium-sized nails. If a dozen of these nails weighs 0.150 lb, how many nails did the customer buy?

Accepted Answer

$$\displaystyle 272\ 	ext{nails}$$

Question 4

How many atoms are present in 3.5 mol of helium?

Accepted Answer

$$\displaystyle 2.1 	imes 10$$^{24}$$\ 	ext{atoms}$$

Question 5

A sample contains $$1.1 	imes 10$$^{22}$$ silver atoms. How many moles of silver are present?

Accepted Answer

$$\displaystyle 1.8 	imes 10$$^{-2}$$\ 	ext{mol}$$

Question 6

Which of the following statements best explains why a mole of large nails weighs more than a mole of small nails, but both contain the same number of nails?

Accepted Answer

The mass of one nail is greater for large nails, but the number of nails in a mole is always the same.

Question 7

How many moles of sulfur are present in 57.8 g of sulfur? (Molar mass of S = 32.07 g/mol)

Accepted Answer

$$\displaystyle 1.80\ 	ext{mol}$$

Question 8

A typical aluminum can has a mass of 16.2 g. How many aluminum atoms does it contain? (Molar mass of Al = 26.98 g/mol)

Accepted Answer

$$\displaystyle 3.62 	imes 10$$^{23}$$\ 	ext{atoms}$$

Question 9

What is the molar mass of carbon dioxide ($$\mathrm{CO_2$}$$)? (Atomic masses: C = 12.01 amu, O = 16.00 amu)

Accepted Answer

$$\displaystyle 44.01\ 	ext{g/mol}$$

Question 10

Calculate the mass in grams of 1.75 mol of water ($$\mathrm{H_2O}). ($$Molar mass of $$\mathrm{H_2O} = 18.02 g/$$mol)

Accepted Answer

$$\displaystyle 31.5\ 	ext{g}$$

Question 11

A 0.358-g sample of chromium reacts with oxygen to form 0.523 g of the metal oxide. What is the mass percent of chromium in the oxide?

Accepted Answer

$$\displaystyle 68.5\%$$

Question 12

A compound is found to contain 60.00% C, 4.48% H, and 35.53% O by mass. What is its empirical formula?

Accepted Answer

$$\displaystyle \mathrm{C_3H_2O}$$

Question 13

A 3.24-g sample of titanium reacts with oxygen to form 5.40 g of the metal oxide. What is the empirical formula of the oxide? (Molar mass: Ti = 47.87 g/mol, O = 16.00 g/mol)

Accepted Answer

$$\displaystyle \mathrm{$$TiO_2$$}$$

Question 14

Fructose has an empirical formula of $$\mathrm{CH_2O}$$ and a molar mass of 180.2 g/mol. What is its molecular formula?

Accepted Answer

$$\displaystyle \mathrm{C_6H_{12}O_6$}$$

Question 15

A variety of Freon contains 69.58% chlorine by mass. How many grams of chlorine are contained in 11.3 g of this substance?

Accepted Answer

$$\displaystyle 7.86\ 	ext{g}$$

Question 16

How many moles of oxygen are in 1 mole of aluminum carbonate ($$\mathrm{Al_2$(CO_3$)_3}$$)?

Accepted Answer

$$\displaystyle 9\ 	ext{mol}$$

Question 17

A compound has an empirical formula of $$\mathrm{C_2H_3O_2}$$ and a molar mass of 118.10 g/mol. What is its molecular formula?

Accepted Answer

$$\displaystyle \mathrm{C_4H_6O_4}$$

Question 18

If a sample of sodium chloride is 39% sodium by mass, how many grams of sodium are in 25.0 g of sodium chloride?

Accepted Answer

$$\displaystyle 9.75\ 	ext{g}$$

Question 19

A 5.85 g sample of an unknown chromium oxide contains 4.00 g of chromium. What is the empirical formula of the oxide? (Molar mass: Cr = 52.00 g/mol, O = 16.00 g/mol)

Accepted Answer

$$\displaystyle \mathrm{Cr_2O_3}$$

Chapter 6: Chemical Composition – Study Notes for Introductory Chemistry

Study Guide - Practice Questions

Study Guide - Flashcards