Chloroethane reacts with $X$ to form diethyl ether. What is $X$?

$0.16 \ g$ of an organic compound containing sulphur produces $0.233 \ g$ of $BaSO_4$. The percentage of sulphur in the compound is:

$A$ square is inscribed in the circle $x^{2} + y^{2} - 2x + 4y - 93 = 0$ such that its sides are parallel to the coordinate axes. The coordinates of its vertices are:

The ionization energy of $He^+$ is $19.6 \times 10^{-18} \ J \ atom^{-1}$. What is the energy of the first stationary state $(n = 1)$ of $Li^{2+}$?

Which one of the following reactions does not occur?

$A$ man of $50\, kg$ mass is standing in a gravity-free space at a height of $10\, m$ above the floor. He throws a stone of $0.5\, kg$ mass downwards with a speed of $2\, m/s$. When the stone reaches the floor,the distance of the man above the floor will be ........ $m.$