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.
11. A solution containing 100 g of H2O and an unknown amount of NaCl boils at 104°C. Based on the results of Experiment 2, the number of moles of NaCl dissolved in the solution is closest to:
Your Answer is
Correct Answer is C
Explanation
From the data in table 2, it can be inferred that for every 0.01 mole of NaCl added, the boiling point will increase by 0.1. So when the boiling point is 104°C, 0.4 mole of NaCl should be added