Ferric sulphate on heating gives:

All wires have the same resistance $r$. The equivalent resistance between $A$ and $B$ is $R$ when the keys $K_1$ and $K_2$ are open. Now,if the keys are closed,what will be the new equivalent resistance?

What is the product formed when phenol reacts with concentrated $HNO_3$?

The distribution of a random variable $X$ is given below:

$X = x$	$-2$	$-1$	$0$	$1$	$2$	$3$
$P(X = x)$	$\frac{1}{10}$	$k$	$\frac{1}{5}$	$2k$	$\frac{3}{10}$	$k$

The value of $k$ is:

Which among the following complexes has square pyramidal geometry?

Which of the following has the lowest melting point?