Two beakers of capacity 500 mL were taken. One of these beakers, labeled as “A”, was filled with 400 mL water whereas the beaker labelled “B” was filled with 400 mL of 2 M solution of NaCl. At the same temperature both the beakers were placed in closed containers of same material and same capacity as shown in Fig. 2.2. At a given temperature, which of the following statement is correct about the vapour pressure of pure water and that of NaCl solution.
NaCl is a non-volatile substance when it is added to the water it increases the boiling point of the water simultaneously decreasing the vapor pressure of the water.
According to Raoult’s law, the partial vapor pressure of each component in the solution is directly proportional to its mole fraction.
Thus, for water as a solvent in a solution
Where Pw is the partial pressure of water and xW is a mole fraction of water in the solution.
Thus, on adding NaCl the mole fraction of water reduces.
Thus, vapor pressure also reduces.
Thus, Option (i) is the correct answer.