Which property of hydrogen distinguishes it from alkali metals?

$A$ vessel contains $1$ mole of $O_2$ gas (molar mass $32$) at a temperature $T$. The pressure of the gas is $P$. An identical vessel containing $1$ mole of $He$ gas (molar mass $4$) at a temperature $2T$ has a pressure of:

The density of water at $20^oC$ is $0.998 \ g/cm^3$ and at $40^oC$ is $0.992 \ g/cm^3$. The mean coefficient of cubical expansion (in per ${}^oC$) is

Two equally charged metal spheres $A$ and $B$ repel each other with a force of $4 \times 10^{-5} ~N$. Another identical uncharged sphere $C$ is touched to $A$ and then placed at the midpoint of the line joining the spheres $A$ and $B$. The net electric force on the sphere $C$ is

The adsorption isotherm for a gas is given by the relation $x = \frac{ap}{1 + bp}$,where $x$ is moles of gas adsorbed per gram of the adsorbent,$p$ is the pressure of the gas,and $a$ and $b$ are constants. Then $x$:

The basic functional unit of the human kidney is