Hydrated $AlCl_3$ is used as:

$\left(\frac{1+i}{1-i}\right)^4+\left(\frac{1-i}{1+i}\right)^4$ is equal to

Four point positive charges of same magnitude $Q$ are placed at four corners of a rigid square frame of side length $L$ as shown in the figure. The plane of the frame is perpendicular to the $Z$-axis. If a negative point charge $-q$ is placed at a distance $z$ away from the centre along the axis $(z << L)$, then:

$C_2H_6 \stackrel{450^{\circ}C}{\longrightarrow} C_2H_4 + H_2$. The above reaction is called:

Which one of the following equations represents the variation of viscosity coefficient $(\eta)$ with temperature $(T)$?

In the ground state,an element has $13$ electrons in the $M$ shell. The element is