Q: Which of the following is the correct percent composition by mass of calcium in calcium acetate, $$\mathrm{Ca(CH_3COO)_2}$$, given $$\mathrm{Ca = 40.08\ g/mol}$$, $$\mathrm{C = 12.01\ g/mol}$$, $$\mathrm{H = 1.01\ g/mol}$$, $$\mathrm{O = 16.00\ g/mol}$$?

$$\frac{40.08}{158.18} \times 100\% = 25.35\%$$

Q: A solution contains 0.154 M NaCl and has a volume of 500 mL. How many moles of NaCl are present?

$$0.154 \times 0.500 = 0.077\ \mathrm{mol}$$

Question 1

Which of the following statements best describes the relationship between molar mass and formula mass for a compound?

Accepted Answer

Formula mass is the mass in amu of one representative particle, while molar mass is the mass in grams of one mole of the compound.

Question 2

Calculate the molar mass of aluminum sulfite, $$\mathrm{Al_2$(SO_3$)_3}$$, using the periodic table values to two decimal places. Which is the correct answer?

Accepted Answer

$$\mathrm{2(26.98) + 3(32.06) + 9(16.00) = 246.16\ g/mol}$$

Question 3

A hydrate of magnesium sulfate has a mass of 13.52 g. After heating, the anhydrate has a mass of 6.60 g. What is the correct formula for the hydrate?

Accepted Answer

$$\mathrm{$$MgSO_4$$ \cdot 7H_2O}$$

Question 4

Which of the following is the correct percent composition by mass of calcium in calcium acetate, $$\mathrm{Ca(CH_3COO)_2}$$, given $$\mathrm{Ca = 40.08\ g/mol}$$, $$\mathrm{C = 12.01\ g/mol}$$, $$\mathrm{H = 1.01\ g/mol}$$, $$\mathrm{O = 16.00\ g/mol}$$?

Accepted Answer

$$\frac{40.08}{158.18} 	imes 100\% = 25.35\%$$

Question 5

A sample of copper(II) sulfate hydrate has a mass of 3.97 g. After heating, the CuSO$$_4$$ that remains has a mass of 2.54 g. What mass of water was driven off?

Accepted Answer

$$3.97\ \mathrm{g} - 2.54\ \mathrm{g} = 1.43\ \mathrm{g}$$

Question 6

Which of the following best describes the empirical formula of a compound?

Accepted Answer

The empirical formula shows the smallest whole number ratio of atoms of each element in a compound.

Question 7

Given a compound with 74.8% carbon and 25.2% hydrogen by mass, what is its empirical formula?

Accepted Answer

$$\mathrm{CH_4$}$$

Question 8

A solution contains 0.154 M NaCl and has a volume of 500 mL. How many moles of NaCl are present?

Accepted Answer

$$0.154 	imes 0.500 = 0.077\ \mathrm{mol}$$

Question 9

Which of the following statements about strong, weak, and nonelectrolytes is correct?

Accepted Answer

Strong electrolytes dissociate completely in water, weak electrolytes dissociate partially, and nonelectrolytes do not dissociate.

Question 10

Which of the following is the correct formula for a hydrate that is 45.43% water by mass and 54.57% CoCl$$_2 by $$mass?

Accepted Answer

$$\mathrm{$$CoCl_2$$ \cdot 4H_2O}$$

Question 11

Which of the following is the correct calculation for the molarity (M) of a solution made by dissolving 1.80 g AgNO$$_3 in $$water to make 75.0 mL of solution? (AgNO$$_3 = 169.88 g/$$mol)

Accepted Answer

$$\frac{1.80}{169.88} \div 0.075 = 0.142\ \mathrm{M}$$

Question 12

Which of the following best describes a supersaturated solution?

Accepted Answer

A solution that contains more solute than would be predicted to dissolve in a given amount of solvent and is unstable.

Question 13

Which equation correctly represents Beer’s Law for spectrophotometry?

Accepted Answer

$$A = ebc$$

Question 14

Which of the following is the correct calculation for the percent by mass of water in nickel(II) chloride hexahydrate, $$\mathrm{$$NiCl_2$$ \cdot 6H_2O}$$, given $$\mathrm{Ni = 58.69\ g/mol}$$, $$\mathrm{Cl = 35.45\ g/mol}$$, $$\mathrm{H_2O = 18.02\ g/mol}$$?

Accepted Answer

$$\frac{6 	imes 18.02}{58.69 + 2 	imes 35.45 + 6 	imes 18.02} 	imes 100\% = 40.48\%$$

Question 15

Which of the following is a correct statement about the effect of temperature on the solubility of gases in water?

Accepted Answer

Solubility of gases in water decreases as temperature increases.

Question 16

Which of the following is the correct calculation for the molar concentration of Na$$^+$$ ions in a solution of Na$$_3PO$_4$$ with a molarity of 0.20 M?

Accepted Answer

$$3 	imes 0.20\ \mathrm{M} = 0.60\ \mathrm{M}$$

General Chemistry Study Guide: Molar Mass, Percent Composition, Hydrates, Empirical & Molecular Formulas, Solutions, and Spectrophotometry

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