2 mole of ideal gas at 27^oC temperature is expanded reversibly from 2 lit. to 20 lit. Find entropy change. (R = 2 cal/mol K)

Solubility of MX₂ type electrolytes is 0.5 $$ \times $$ 10^$$-$$4 mole/lit., then find out K_sp of electrolytes.

Which has highest pH?

Solution of 0.1 N NH₄OH and 0.1 N NH₄Cl has pH 9.25. Then find out pK_b of NH₄OH