Which of the following is paramagnetic and contains a three-electron bond in its structure?

The species with spin only magnetic moment of $\sqrt{24} \ BM$ is

If the values of $\Lambda_{\infty}$ of $NH_4Cl, NaOH$ and $NaCl$ are $130, 217$ and $109 \ \Omega^{-1} \ cm^2 \ equiv^{-1}$ respectively,the $\Lambda_{\infty}$ of $NH_4OH$ in $\Omega^{-1} \ cm^2 \ equiv^{-1}$ is

The reading of the ammeter in the circuit shown will be: (in $A$)

$A$ monoatomic gas is suddenly compressed to $(1/8)^{\text{th}}$ of its initial volume adiabatically. The ratio of the final pressure to initial pressure of the gas is (given $\gamma = 5/3$).

If $a, b, c$ are non-coplanar unit vectors such that $a \times (b \times c) = \frac{b + c}{\sqrt{2}}$,then what is the angle between $a$ and $b$?