∆_fU $°$ of formation of CH₄ (g) at certain temperature is –393 kJ/mol. The value of ∆_fH $°$ is

(i) zero

(ii) < ∆_f U $°$

(iii) > ∆_f U $°$

(iv) Equal to ∆_fU $°$

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