Which from following reagents is used in the conversion of phenol to picric acid?

Which element from following has largest atomic size as compared to other three?

Calculate the enthalpy change when 12 g carbon react with sufficient hydrogen to form methane. If enthalpy of formation of methane is $-75 \mathrm{~kJ} \mathrm{~mol}^{-1}$.

What type of ligand is the oxalate ion?