28. Reaction spontaneous at all temperatures when:

(a) Δ_rH^? is negative, Δ_rS^? positive, Δ_rG^? is negative.

(b) Δ_rH^? is positive, Δ_rS^? positive, Δ_rG^? is negative.

(c) Δ_rH^? is negative, Δ_rS^? positive, Δ_rG^? is positive.

(d) Δ_rH^? is positive, Δ_rS^? positive, Δ_rG^? is positive.

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