If the density of the earth is doubled keeping its radius constant,then acceleration due to gravity will be ........ $m/s^2$. $(g = 9.8\,m/s^2)$

If the function $f$ defined by $f(x) = K(x - x^2)$ for $0 < x < 1$ and $f(x) = 0$ otherwise,is the probability density function (p.d.f.) of a random variable $X$,then the value of $P(X < \frac{1}{2})$ is

$A$ liquid is in equilibrium with its vapour in a sealed container at a fixed temperature. The volume of the container is suddenly increased.
$a$. What is the initial effect of the change on vapour pressure?
$b$. How do rates of evaporation and condensation change initially?
$c$. What happens when equilibrium is restored finally and what will be the final vapour pressure?

What is formed when $HCOOH$ reacts with concentrated $H_2SO_4$?

There are $9$ balls to be placed in $9$ boxes. If $5$ of the balls cannot fit into $3$ specific small boxes,find the number of ways of arranging one ball in each of the boxes.