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Home » 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 the same material and same capacity as shown in Figure. At a given temperature, which of the following statement is correct about the vapour pressure of pure water and that of NaCl solution.
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 the same material and same capacity as shown in Figure. At a given temperature, which of the following statement is correct about the vapour pressure of pure water and that of NaCl solution.
CBSE | Chemistry | Class 12 | Exercise 1 | NCERT Exemplar | Solutions
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 the same material and same capacity as shown in Figure. At a given temperature, which of the following statement is correct about the vapour pressure of pure water and that of NaCl solution.

(i) the vapour pressure in container (A) is more than that in a container (B).

(ii) the vapour pressure in container (A) is less than that in the container (B).

(iii) vapour pressure is equal in both containers.

(iv) the vapour pressure in container (B) is twice the vapour pressure in container (A).

 

Correct Answer: (i) the vapour pressure in container (A) is more than that in a container (B)

Explanation: When salt is added to water to form a solution, the vapor pressure of the solution is reduced. This is because the deterioration of the surface covered by the solvent molecule leads to a decrease in the number of solvent molecules that escape the surface associated with the pure solvent. It should be noted that NaCl is a stable solute and will reduce the pressure of the solution. Therefore, the pressure of pure water vapor in container A is higher than in container B. Therefore, the vapor pressure also decreases.

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