Solubility and Colligative Properties: Quiz

Solubility and Colligative Properties: Quiz

7 questions

1. Question 1EasyWhy do fizzy drinks go flat faster when warm?

   Agases are more soluble when warmBgases are less soluble when warmCsugar reacts with CO₂Dwater evaporates
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   Answer: gases are less soluble when warm

   Gas solubility falls as temperature rises, so CO₂ escapes faster from a warm drink.

2. Question 2EasyWhat is the molality of 0.500 mol of glucose in 250. g of water?

   A0.125 mol/kgB0.500 mol/kgC2.00 mol/kgD2.00 × 10⁻³ mol/kg
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   Answer: 2.00 mol/kg

   m = 0.500 mol ÷ 0.250 kg = 2.00 mol/kg. Remember to convert grams to kilograms.

3. Question 3MediumWhich 0.10 mol/kg solution has the lowest freezing point?

   AglucoseBNaClCCaCl₂Dsucrose
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   Answer: CaCl₂

   CaCl₂ gives 3 ions (i = 3), the most particles, so the largest freezing-point depression.

4. Question 4MediumA 1.00 mol/kg aqueous glucose solution freezes at (Kf = 1.86 °C kg/mol):

   A+1.86 °CB−1.86 °CC−0.512 °CD−3.72 °C
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   Answer: −1.86 °C

   ΔTf = 1 × 1.86 °C kg/mol × 1.00 mol/kg = 1.86 °C; 0.00 °C − 1.86 °C = −1.86 °C.

5. Question 5MediumWhat is the van 't Hoff factor of Na₂SO₄ (ideal)?

   A1B2C3D7
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   Answer: 3

   Na₂SO₄ → 2Na⁺ + SO₄²⁻: three ions. The sulfate ion stays together.

6. Question 6EasyWhich unit of temperature must be used in Π = iMRT?

   A°CB°FCKDany unit
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   Answer: K

   R = 0.08206 L atm mol⁻¹ K⁻¹ contains kelvin, so T must be in kelvin for the units to cancel.

7. Question 7HardWhy is molality, not molarity, used for boiling- and freezing-point calculations?

   Ait is easier to measure volumeBmolality does not change with temperatureCmolarity has no unitsDmolality includes the solute mass
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   Answer: molality does not change with temperature

   Molality uses mass of solvent, which does not change on heating; volumes expand, so molarity changes.