Consider the reactions given below. On the basis of these reactions find out which of the algebric relations given in options (i) to (iv) is correct?

(a) C (g) + 4H (g) → CH₄ (g); ∆r H = x kJ/ mol

(b) C (graphite,s) + 2H₂ (g) → CH₄ (g); ∆rH = y kJ /mol

(i) x = y

(ii) x = 2y

(iii) x > y

(iv) x < y

HCP crystal is made of A ions and B ions are arranged in 2/3rd of octahedral voids. The simplest formula of compound is :-

Which of the following is a carbonate ore ?

Which of the following complex is paramagnetic, inner orbital complex and coloured :-

The orbital angular momentum of 3d electron is

For the reaction, CaCO₃(s) → CaO(s) + CO₂(g) △H = 82.8 kJ at 25°C, △U at 25°C is