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Chemistry 20

Chemistry 20 · Worksheets

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Ten questions of mixed difficulty, covering Solutions. Print it, or work through it on screen — the answer key starts on its own page.

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Chemistry 20 · maddyhelps.com

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  1. Diluting 50.0 mL of 2.00 mol/L solution to 200.0 mL gives a concentration of

    1. a) 0.125 mol/L
    2. b) 0.500 mol/L
    3. c) 1.00 mol/L
    4. d) 8.00 mol/L

  2. Of these, the compound that is insoluble in water is

    1. a) KNO₃
    2. b) NaCl
    3. c) NH₄Cl
    4. d) AgCl

  3. A saturated solution is one that

    1. a) holds more solute than it should be able to
    2. b) has a concentration of exactly 1 mol/L
    3. c) holds the maximum solute that will dissolve at that temperature
    4. d) contains no undissolved solid

  4. The mass of NaCl needed to make 500.0 mL of 0.200 mol/L solution is about

    1. a) 2.9 g
    2. b) 0.10 g
    3. c) 5.8 g
    4. d) 11.7 g

  5. In a 0.10 mol/L solution of Na₂SO₄, the concentration of sodium ions is

    1. a) 0.40 mol/L
    2. b) 0.20 mol/L
    3. c) 0.10 mol/L
    4. d) 0.05 mol/L

  6. When solutions of AgNO₃ and NaCl are mixed, the net ionic equation is

    1. a) Na⁺(aq) + NO₃⁻(aq) → NaNO₃(s)
    2. b) Ag⁺(aq) + Cl⁻(aq) → AgCl(s)
    3. c) Ag⁺(aq) + NO₃⁻(aq) → AgNO₃(s)
    4. d) AgNO₃(aq) + NaCl(aq) → AgCl(s) + NaNO₃(aq)

  7. Dissolving 0.50 mol of solute in enough water to make 2.0 L of solution gives a concentration of

    1. a) 4.0 mol/L
    2. b) 0.25 mol/L
    3. c) 2.5 mol/L
    4. d) 1.0 mol/L

  8. In a solution, the solute is

    1. a) the substance doing the dissolving
    2. b) always water
    3. c) always a solid
    4. d) the substance that is dissolved

  9. Of these, the substance least likely to dissolve in water is

    1. a) KNO₃
    2. b) vegetable oil
    3. c) NaCl
    4. d) sugar

  10. Molar concentration is measured in

    1. a) mol
    2. b) L/mol
    3. c) mol/L
    4. d) g/L

Answer key · Solutions

Chemistry 20 · maddyhelps.com

  1. b) 0.500 mol/L — Dilution does not change the amount of solute, so c₁V₁ = c₂V₂ and c₂ = (2.00)(50.0)/200.0 = 0.500 mol/L. Quadrupling the volume divides the concentration by four.
  2. d) AgCl — Most chlorides are soluble, but the silver, lead and mercury(I) ones are the standard exceptions — which is why mixing silver nitrate with any chloride gives a white precipitate. All nitrates, all sodium compounds and all ammonium compounds are soluble.
  3. c) holds the maximum solute that will dissolve at that temperature — At saturation, dissolving and crystallizing happen at the same rate, so adding more solute just leaves it sitting on the bottom. The maximum depends on temperature, which is why it must be stated.
  4. c) 5.8 g — First n = cV = (0.200)(0.5000) = 0.100 mol. Then m = nM = (0.100)(58.44) = 5.8 g. Volume has to be in litres before it is multiplied by a concentration in mol/L.
  5. b) 0.20 mol/L — Each formula unit releases two Na⁺ and one SO₄²⁻, so the sodium concentration is twice the concentration of the compound. Ion concentrations follow the subscripts in the formula.
  6. b) Ag⁺(aq) + Cl⁻(aq) → AgCl(s) — A net ionic equation shows only what changes. Silver and chloride ions come together as a solid; everything else stays dissolved and unchanged, so it is left out.
  7. b) 0.25 mol/L — c = n/V = 0.50/2.0 = 0.25 mol/L. Note that the volume is the volume of the final solution, not the volume of water added — those are slightly different things.
  8. d) the substance that is dissolved — The solute dissolves and the solvent does the dissolving, usually the component present in greater amount. A solute can be a solid, a liquid or a gas — carbonated water has a dissolved gas.
  9. b) vegetable oil — Oil is non-polar, so water molecules have nothing to grip onto and prefer to stick to each other. The other three are either ionic or polar enough to be surrounded by water molecules.
  10. c) mol/L — Molar concentration is amount of solute per litre of solution, so mol/L. Grams per litre is a concentration too, but it is not molar concentration and cannot be used directly in stoichiometry.