Q: A water sample contains 1 ppm arsenic (As) by mass. What is the molar concentration of arsenic in the water? (Assume density of water is $$1.00\ \mathrm{g/mL}$$, molar mass of As = 74.92 g/mol, and 1 ppm = 1 mg/L)

$$1.34 \times 10$$^{-5}$$\ \mathrm{mol/L}$$

Question 1

A 87.12 mg sample of a compound containing only carbon, hydrogen, and oxygen is combusted, producing 198.05 mg of $$\mathrm{CO_2$}$$ and 81.09 mg of $$\mathrm{H_2O}. $$What is the empirical formula of the compound?

Accepted Answer

$$\mathrm{C_3H_6O_2}$$

Question 2

How many grams of $$\mathrm{CO_2$}$$ are produced when 15.0 g of hexane ($$\mathrm{C_6H_{14}}) is $$completely combusted in excess oxygen? (Molar mass of $$\mathrm{C_6H_{14}} = 86.18 g/$$mol)

Accepted Answer

46.2 g

Question 3

A 15.00 g sample of a hydrocarbon is combusted, producing 45.43 g of $$\mathrm{CO_2$}$$ and 23.25 g of $$\mathrm{H_2O}. $$What is the empirical formula of the hydrocarbon?

Accepted Answer

$$\mathrm{C_3H_8}$$

Question 4

What is the molarity of a sugar solution prepared by dissolving 0.15 moles of sugar in 0.175 L of solution?

Accepted Answer

$$0.857\ \mathrm{M}$$

Question 5

How many liters of a 0.235 M sugar solution can be prepared with 0.470 moles of sugar?

Accepted Answer

2.00 L

Question 6

A salt solution is prepared by dissolving 18.65 g of $$\mathrm{NaCl} in $$water to make 250.0 mL of solution. What is the molarity of the solution? (Molar mass of $$\mathrm{NaCl} = 58.44 g/$$mol)

Accepted Answer

$$1.28\ \mathrm{M}$$

Question 7

The solution in the previous question is diluted to a final volume of 1.000 L. What is the new molarity?

Accepted Answer

$$0.320\ \mathrm{M}$$

Question 8

What volume of 3.15 M $$\mathrm{NaOH}$$ solution is needed to prepare 250. mL of 0.150 M $$\mathrm{NaOH}$$ solution?

Accepted Answer

11.9 mL

Question 9

A water sample contains 1 ppm arsenic (As) by mass. What is the molar concentration of arsenic in the water? (Assume density of water is $$1.00\ \mathrm{g/mL}$$, molar mass of As = 74.92 g/mol, and 1 ppm = 1 mg/L)

Accepted Answer

$$1.34 	imes 10$$^{-5}$$\ \mathrm{mol/L}$$

Question 10

Which of the following best describes a dissociation reaction?

Accepted Answer

A reaction in which a compound breaks apart into its ions in solution

Question 11

Which of the following is the characteristic identifying feature of a precipitation reaction?

Accepted Answer

A solid forms from the mixing of two solutions

Question 12

Which cations generally form soluble ionic compounds according to solubility rules?

Accepted Answer

$$\mathrm{Na^+}$$, $$\mathrm{K^+}$$, $$\mathrm{NH_4$^+}$$

Question 13

Which anions generally form soluble ionic compounds according to solubility rules?

Accepted Answer

$$\mathrm{NO_3$^-}$$, $$\mathrm{$$ClO_4$$^-}$$, $$\mathrm{CH_3COO^-}$$

Question 14

Which anions generally form insoluble ionic compounds according to solubility rules?

Accepted Answer

$$\mathrm{CO_3$^{2-}}$$, $$\mathrm{PO_4$^{3-}}$$, $$\mathrm{S$$^{2-}$$}$$

Question 15

Which of the following is an exception to the general solubility rule for chlorides ($$\mathrm{Cl^-}$$)?

Accepted Answer

Chlorides of $$\mathrm{Ag^+}$$

Question 16

When aqueous solutions of lead(II) acetate and sodium carbonate are mixed, what is the balanced net ionic equation for the reaction?

Accepted Answer

$$\mathrm{Pb$$^{2+}$$ (aq) + CO_3$^{2-} (aq) \rightarrow $$PbCO_3$$ (s)}$$

Question 17

Which of the following best describes what happens when calcium chloride and sodium phosphate solutions are mixed?

Accepted Answer

A precipitate of $$\mathrm{Ca_3$(PO_4$)_2}$$ forms

Question 18

Which of the following is the balanced molecular equation for the reaction between ammonium chloride and copper(II) sulfate in water?

Accepted Answer

$$\mathrm{2NH_4Cl (aq) + $$CuSO_4$$ (aq) \rightarrow (NH_4$)_2SO_4 (aq) + $$CuCl_2$$ (aq)}$$

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