Which of the following has the highest mass?

Which of the following compounds does not have similarity in their structural aspect?

The normality of $H_{2}SO_{4}$ in the solution obtained on mixing $100 \ mL$ of $0.1 \ M \ H_{2}SO_{4}$ with $50 \ mL$ of $0.1 \ M \ NaOH$ is $\times 10^{-1} \ N$. (Nearest Integer)

Which of the following has the maximum mass?

$16 \ g$ each of $H_2$,$He$,and $O_2$ are present in a container exerting $10 \ atm$ pressure at $T \ (K)$. The pressure in $atm$ exerted by $16 \ g$ each of $He$ and $O_2$ in the second container of same volume and temperature is

Write formulas for the following compounds:
$(1)$ Mercury $(II)$ chloride
$(2)$ Nickel $(II)$ sulphate
$(3)$ Tin $(IV)$ oxide
$(4)$ Thallium $(I)$ sulphate