Which of the following species has the highest electron affinity?

$A$ uniform metal rod of $2\,mm^2$ cross-section fixed between two walls is heated from $0\,^{\circ}C$ to $20\,^{\circ}C$. The coefficient of linear expansion of the rod is $12 \times 10^{-6}\,/^{\circ}C$. Its Young's modulus of elasticity is $10^{11}\,N/m^2$. The energy stored per unit volume of the rod will be ....... $J/m^3$.

Which of the following is a favourable factor for cation formation?

(in $\%$)

Energy is being emitted from the surface of a black body at $127^{\circ}C$ temperature at the rate of $1.0 \times 10^6 \ J/\text{s} \cdot \text{m}^2$. The temperature of the black body at which the rate of energy emission is $16.0 \times 10^6 \ J/\text{s} \cdot \text{m}^2$ will be ......... $^{\circ}C$.

In $\triangle ABC$,if $\frac{1}{b+c} + \frac{1}{c+a} = \frac{3}{a+b+c}$,then $C$ is equal to (in $^{\circ}$)