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Chemistry 20

Chemistry 20 · Worksheets

Mixed review · Gases, solutions, acids and bases

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

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Mixed review · Gases, solutions, acids and bases

Chemistry 20 · maddyhelps.com

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  1. A 25.0 mL sample of HCl is exactly neutralized by 20.0 mL of 0.100 mol/L NaOH. The concentration of the acid is

    1. a) 0.0500 mol/L
    2. b) 0.0800 mol/L
    3. c) 0.125 mol/L
    4. d) 0.100 mol/L

  2. 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) 8.00 mol/L
    3. c) 1.00 mol/L
    4. d) 0.500 mol/L

  3. A 2.0 g sample of a gas occupies 1.24 L at SATP. Its molar mass is

    1. a) 40 g/mol
    2. b) 62 g/mol
    3. c) 2.0 g/mol
    4. d) 24.8 g/mol

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

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

  5. The molar volume of an ideal gas at SATP is

    1. a) 24.8 mL/mol
    2. b) 101.3 L/mol
    3. c) 24.8 L/mol
    4. d) 22.4 L/mol

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

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

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

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

  8. Acids turn

    1. a) red litmus blue
    2. b) litmus green
    3. c) blue litmus red
    4. d) litmus colourless

  9. A saturated solution is one that

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

  10. According to the kinetic molecular theory, the particles of an ideal gas

    1. a) are in constant random motion and have negligible volume of their own
    2. b) all move at exactly the same speed
    3. c) attract each other strongly
    4. d) are closely packed and vibrate in place

Answer key · Mixed review · Gases, solutions, acids and bases

Chemistry 20 · maddyhelps.com

  1. b) 0.0800 mol/L — The base supplies n = (0.100)(0.0200) = 2.00 × 10⁻³ mol. HCl and NaOH react 1:1, so the acid sample contained the same amount, and c = 2.00 × 10⁻³/0.0250 = 0.0800 mol/L. The mole ratio has to be checked — it is not 1:1 for every acid.
  2. d) 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.
  3. a) 40 g/mol — First the amount: n = 1.24/24.8 = 0.050 mol. Then M = m/n = 2.0/0.050 = 40 g/mol. Molar volume is the bridge from a measured volume to an amount whenever the gas is at SATP.
  4. 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.
  5. c) 24.8 L/mol — SATP is 25 °C and 100 kPa, giving 24.8 L/mol. The familiar 22.4 L/mol is the value at STP, 0 °C and 101.325 kPa. Alberta questions usually specify which, and the two are not interchangeable.
  6. 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.
  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. c) blue litmus red — The rhyme worth keeping is that acids turn litmus red. Bases do the reverse. Litmus only tells you which side of neutral you are on, not how far.
  9. a) 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.
  10. a) are in constant random motion and have negligible volume of their own — The model treats particles as points that fly about at random and only interact by colliding. Real gases depart from it at high pressure and low temperature, where volume and attractions stop being negligible.