A polymer which becomes soft on heating and hard on cooling, belongs to class of

The effective atomic number of $\operatorname{Iron}(z=26)$ in $\left[\mathrm{Fe}(\mathrm{CN})_6\right]^{-3}$ is

Which bond in a molecule of ethyl magnesium bromide is ionic in nature?

Based on first law of thermodynamics which of the following is correct