Which of the following pairs is mismatched?

The alum used for purifying water is

Which one of the following is not an iso-electronic pair?

What is a capsomere?

Two cylinders $A$ and $B$ fitted with pistons contain equal amounts of an ideal diatomic gas at temperature $T \ K$. The piston of cylinder $A$ is free to move,while that of cylinder $B$ is held fixed. The same amount of heat $dQ$ is given to the gas in each cylinder. If the rise in temperature of the gas in $A$ is $dT_{A}$,then the rise in temperature of the gas in $B$ is (where $\gamma = \frac{C_{p}}{C_{v}}$):

The first line in the Lyman series has wavelength $\lambda$. The wavelength of the first line in the Balmer series is: