Passage III
A mole is 6 x 1023 molecules or formula units of a compound. Thus, the number of sucrose molecules in 1 mole of sucrose equals the number of NaCl units in 1 mole of NaCl. Molality (m) is a unit of concentration defined as:
When a substance is dissolved in a solvent, the freezing and boiling points of the solution will differ from those of the pure solvent. These changes depend on the concentration show how the freezing point and the boiling point, respectively, of H2O at 1 atm of pressure vary with concentration for 3 solutes.
15. Based on Figure 1, the freezing point of a solution composed of 1.20 moles of NaCl dissolved in 1 kg of H2O would be closest to which of the following?
Your Answer is
Correct Answer is B
Explanation
Put value questions. Look at figure 1, when the abscissa is 1.20, the ordinate corresponding to NaCl is about -5.7°C