5. The enthalpy of combustion of methane, graphite and dihydrogen at 298 K are -890.3 KJ mol^-1, – 393.5 KJ mol^-1 and – 285.8 KJ mol^-1 respectively. Enthalpy of formation of CH₄(g) will be

(i) – 74.8 KJ mol^-1                                         

(ii) – 52.27 KJ mol^-1

(iii) + 74.8 KJ mol^-1                                 

(iv) + 52.26 KJ mol^-1    

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