$NaOH$ is prepared by which of the following methods?

The coefficient of apparent expansion of mercury in a glass vessel is $153 \times 10^{-6}/^{\circ}C$ and in a steel vessel is $144 \times 10^{-6}/^{\circ}C$. If $\alpha$ for steel is $12 \times 10^{-6}/^{\circ}C$,then $\alpha$ for glass is:

Two point charges $-q$ and $+q$ are located at points $(0, 0, -a)$ and $(0, 0, a)$ respectively. The electric potential at a point $(0, 0, z)$,where $z > a$ is

In which of the following reactions is benzaldehyde formed from benzoyl chloride and hydrogen in the presence of $Pd/BaSO_4$?

This is the $1^{st}$ and $2^{nd}$ exam question.

If the slope of one of the lines given by $ax^2+2hxy+by^2=0$ is two times the other,then: