Heating phthalic anhydride and concentrated sulfuric acid with which of the following yields phenolphthalein?

Which of the following reactions will $NOT$ occur with heated copper at $300\,^\circ C$?

$A$ wire in the form of a square of side $a$ carries a current $i$. Then,the magnetic induction at the centre of the square is (Magnetic permeability of free space $= \mu_0$)

$A$ fully charged capacitor $C$ with initial charge $q_0$ is connected to a coil of self-inductance $L$ at $t = 0$. The time at which the energy is stored equally between the electric and the magnetic fields is

At temperature $T \ K$,the $rms$ speed of $CO_2$ gas is $x \ cm/s$. At what temperature (in $Kelvin$) will the $rms$ speed of nitrous oxide $(N_2O)$ be $4x \ cm/s$ (in $T$)?

Phototropic curvature is the result of uneven distribution of