If the normal to the curve $y=f(x)$ at the point $(3,4)$ makes an angle of $\frac{3 \pi}{4}$ with the positive $X$-axis,then the value of $f^{\prime}(3)$ is

The active mass of $64 \ g$ of $HI$ in a $2 \ L$ flask is:

In which of the following pairs,the central atoms have the same number of lone pairs of electrons?

$AB$ crystallizes in a body-centred cubic lattice with edge length '$a$' equal to $387 \ pm$. The distance between two oppositely charged ions in the lattice is ............. $pm$.

Given in the figure are two blocks $A$ and $B$ of weight $20 \, N$ and $100 \, N$,respectively. These are being pressed against a wall by a force $F$ such that the system does not slide as shown. If the coefficient of friction between the blocks is $0.1$ and between block $B$ and the wall is $0.15$,the frictional force applied by the wall on block $B$ is ........ $N$.

If $(2,-1,3)$ is the foot of the perpendicular drawn from the origin to the plane,then the equation of the plane is