Which of the following species is not electrophilic in nature?

The radiation emitted by a star $A$ is $10,000$ times that of the sun. If the surface temperatures of the sun and the star $A$ are $6000 \ K$ and $2000 \ K$ respectively,the ratio of the radii of the star $A$ and the sun is (in $:1$)

Which of the following substances has the highest melting point?

Which of the following reagents will convert propanoic acid to propan-$1$-ol?

$A$ mixture of $2\, \text{moles}$ of helium gas (atomic mass $= 4\, \text{amu}$) and $1\, \text{mole}$ of argon gas (atomic mass $= 40\, \text{amu}$) is kept at $300\, \text{K}$ in a container. The ratio of the $r.m.s.$ speeds $\left( \frac{v_{\text{rms}}(\text{helium})}{v_{\text{rms}}(\text{argon})} \right)$ is

If $f(x) = \frac{1}{x^2} \int_3^x (2t - 3f'(t)) dt$,then $f'(3)$ is equal to