Question

Equilibrium constant for the following equilibrium is given at 0⁰C.

Na2HPO4 . 12H2O (s) $\rightleftharpoons$ Na2HPO4 .

7H2O (s) + 5H2O(g) KP = 31.25 × 10–13

At equilibrium what will be partial pressure of water vapour:

• A. $\frac{1}{5}$ ×10–3 atm
• B. 0.5 × 10–3 atm
• C. 5 × 10–2 atm
• D. 5 × 10–3 atm.

Answer 1

Answer: (D)

5 × 10–3 atm.

Answer 2

Na2HPO4 .12H2O(s) Na2HPO4.7H2O (s) + 5H2O (g) KP = 31.25×10–13

}{\left( P_{H_{2}O} \right)^{5} = 31.25 \times 10^{- 3} }{\left( P_{H_{2}O} \right) = (3125)^{1/5} \times \left( 10^{- 15} \right)^{1/5} }{\left( P_{H_{2}O} \right) = 5 \times 10^{- 3}}$$