Answers to Practice Questions

1. Is bronze a solution? Explain.

   Yes, it is a solution of different metals, all in the solid state.

2. If solute B changes the boiling point three times as much as solute A for the same amount of each, what can you say about the number of particles formed from A compared to the number of particles formed from B? Explain and give some sample calculations.

   Since the change in boiling point is directly proportional to the number of particles placed in the solution, B must form three times as many particles as A.

   For a water solution that is 1 m in sugar, which dissolves into molecules and only provides one particle:

   ΔT_b = K_b m = (0.52 °C/m)(1.0 m) = 0.52 °C

   For a water solution that is 1 m in MgCl₂, which dissolves into ions and provides three particles:

   ΔT_b = K_b m = (0.52 °C/m)(3.0 m) = 1.56 °C

3. Why is CaCl₂ put on roads and sidewalks to melt the ice instead of NaCl?

   CaCl₂ provides three particles while NaCl only provides two.

4. Why don't you use straight antifreeze in your radiator?

   Antifreeze mixed with water will have a lower freezing point than either pure water or pure antifreeze due to the particles of the one that are dissolved in the other.

5. Why do cooks put salt in the water before putting in the spagetti?

   It might make it taste better and maybe keep it from sticking as much, but it would also raise the boiling point, allowing the water to get hotter, and cooking the spagetti faster.

6. Why don't some popsicles get as hard as regular ice cubes?

   The popsicles have particles dissolved in them which lowers the freezing point.