The oxidation states of iron atoms in compounds (A), (B) and (C), respectively, are x, y and z. The sum of x, y and z is ________.

Na₄[Fe(CN)₅(NOS)]
       (A)

Na₄[FeO₄]
       (B)

[Fe₂(CO)₉]
       (C)

The internal energy change (in J) When 90 g of water undergoes complete evaporation at 100^oC is ____________.

(Given : $$\Delta $$H_vap for water at 373 K = 41 kJ/mol,
R = 8.314 JK^–1 mol^–1)

The number of chiral carbons present in the molecule given below is _____ .

The increasing order of the following compounds towards HCN addition is :