Which pair does not show hydrogen isotopes?

Which compound is used in hydrogen generators?

The vapor pressure of $......$ is maximum.

Which of the following acids exhibits oxidizing,reducing,and complex-forming properties?

Fill in the blanks:
$(1)$ In the crystal structure of ice, the oxygen atom is at a distance of $276 \ pm$ from four hydrogen atoms.
$(2)$ The relative proportion of tritium to protium is $1: 10^{18}$.

Which type of ions are present in the anhydrous mixture of $KF$ and $HF$?