What is the correct order of stability for the superoxides?

An ideal gas is expanding such that $PT^2 =$ constant. The coefficient of volume expansion of the gas is

If $P = \begin{bmatrix} 1 & \alpha & 3 \\ 1 & 3 & 3 \\ 2 & 4 & 4 \end{bmatrix}$ is the adjoint of a $3 \times 3$ matrix $A$ and $|A| = 4$,then $\alpha$ is equal to

The amount of copper metal deposited at the cathode on passing an electric current of $500 \, mA$ for $20 \, minutes$ in a cupric chloride solution is ............ $g$.

If $\overrightarrow{a}+\overrightarrow{b}+\overrightarrow{c}=\overrightarrow{0}$ and $|\overrightarrow{a}|=3, |\overrightarrow{b}|=4$ and $|\overrightarrow{c}|=\sqrt{37}$,then the angle between $\overrightarrow{a}$ and $\overrightarrow{b}$ is:

Which structure acts as the pacemaker of the heart?