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.

14. According to the results of Experiments 1 and 2, which of the following conclusions can be made about the magnitudes of the changes in the boiling point and freezing point of H2O solutions when 0.2 mole of NaCl is added to 100 g of H2O ? The freezing point is:

Answer and Explanation

Your Answer is

Correct Answer is J

Explanation

Observing table 1 & table 2, it can be found that after adding 0.2 mole of NaCl, the freezing point decreased by 6.9°C, while the boiling point increased by 2.0°C. So the freezing point drops more than the boiling point rises