In Haber's process of production of ammonia, $\mathrm{K}_2 \mathrm{O}$ is used as

An ideal gas expands against constant external pressure of 2 bar from 5 lit to 8 lit and absorbs 10 kJ of heat. What is $\Delta \mathrm{U}$ of the system?

Which of the following compounds follows octet rule?

Identify the type of hybridization present in $\left[\mathrm{Ni}(\mathrm{CN})_4\right]^{2-}$.