$K_2MnO_4$ can be converted into $KMnO_4$ by

The thickness of a uniform rectangular metal plate is $5 ~mm$ and the area of each surface is $5 ~cm^2$. In steady state, the temperature difference between the two surfaces of the plate is $14^{\circ} C$. If the heat flowing through the plate in one second from one surface to the other surface is $42 ~J$, then the thermal conductivity of the metal is:

From the top of a tower of height $40 \ m$,a ball is projected upwards with a speed of $20 \ m/s$ at an angle $30^{\circ}$ to the horizontal. The ball will hit the ground in time ......... $\sec$ (Take $g = 10 \ m/s^2$)

What is the chemical formula of Glauber's salt?

In which of the following reactions,$MgO$ is not formed?

If $\sin^{-1}(\frac{x}{5}) + \csc^{-1}(\frac{5}{4}) = \frac{\pi}{2}$,then $x = $