50 mL of 0.1 M CH_{3}COOH is being titrated against 0.1 M NaOH. When 25 mL of NaOH has been added, the pH of the solution will be _____________ $$\times$$ 10^{$$-$$2}. (Nearest integer)

(Given : pK_{a} (CH_{3}COOH) = 4.76)

log 2 = 0.30

log 3 = 0.48

log 5 = 0.69

log 7 = 0.84

log 11 = 1.04

PCl_{5} dissociates as

PCl_{5}(g) $$\rightleftharpoons$$ PCl_{3}(g) + Cl_{2}(g)

5 moles of PCl_{5} are placed in a 200 litre vessel which contains 2 moles of N_{2} and is maintained at 600 K. The equilibrium pressure is 2.46 atm. The equilibrium constant K_{p} for the dissociation of PCl_{5} is __________ $$\times$$ 10^{$$-$$3}. (nearest integer)

(Given : R = 0.082 L atm K^{$$-$$1} mol^{$$-$$1}; Assume ideal gas behaviour)

2O_{3}(g) $$\rightleftharpoons$$ 3O_{2}(g)

At 300 K, ozone is fifty percent dissociated. The standard free energy change at this temperature and 1 atm pressure is ($$-$$) ____________ J mol^{$$-$$1}. (Nearest integer)

[Given : ln 1.35 = 0.3 and R = 8.3 J K^{$$-$$1} mol^{$$-$$1}]

_{2}in 0.1 M NaOH solution is x $$\times$$ 10

^{$$-$$18}M. The value of x is _________ (Nearest integer)

(Given : The solubility product of Zn(OH)

_{2}is 2 $$\times$$ 10

^{$$-$$20})