Passage III

The following experiments were performed to investigate the effects of adding various solutes (substances that are dissolved in a solution), in varying amounts, on the boiling points and freezing points of H2O solutions. Pure H2O freezes at 0°C and boils at 100°C at standard atmospheric pressure.

Experiment 1

A student dissolved 0.01 mole of sodium chloride (NaCl) in 100 g of H2O. Each mole of NaCl produces 2 moles of solute particles (1 mole of sodium ions and 1 mole of chloride ions in solution). After the NaCl dissolved, the freezing point of the solution was determined. This procedure was repeated using different amounts of NaCl and table sugar (sucrose). Each mole of sucrose produces 1 mole of solute particles (sucrose molecules). The results are shown in Table 1.

Experiment 2

A student dissolved 0.01 mole of NaCl in 100 g of H2O. After the NaCl dissolved, the boiling point of the solution was determined. The procedure was repeated using various amounts of NaCl. The results are shown in Table 2.

16. CaCl2 produces 3 moles of solute particles per mole when dissolved. Experiment 1 was repeated using a solution containing 100 g of H2O and 0.1 mole CaCl2. Assuming that CaCl2 has the same effect on the freezing point of H2O as does NaCl per particle produced when dissolved, the freezing point of the solution would most likely be:

Answer and Explanation

Your Answer is

Correct Answer is H

Explanation

Because the question stem assumes that each particle has the same effect on the freezing point, and CaCl2 has three particles, NaCl has two, then 0.1 mole CaCl2 The effect is equivalent to that of 0.15 mole NaCl. So the freezing point should be between -3.4 and -6.9°C