14. Solving a chemistry problem

7. Write the reaction equations in a short ionic form, express the equilibrium constants of these reactions (in terms of the corresponding Ka, Kb and Pr) and find the numerical values:
a) KCN H2O CO2 → HCN KHCO3;
b) NH3 H2S → (NH4)2S;
c) Mg(OH)2(solid) 2NH4ClO4 → Mg(ClO4)2 2NH3 2H2O;
d) Mg(OH)2(solid) 2HClO4 → Mg(ClO4)2 2H2O;
e) 2Cr(NO3)3 3Na2S 6H2O → 2Cr(OH)3(s) 2H2S 6NaNO3.
Which of these reactions are irreversible?