The least value of the natural number $n$ satisfying $C(n, 5) + C(n, 6) > C(n+1, 5)$ is

When a non-volatile solute is added to a solvent,the vapor pressure of the solvent decreases by $10 \ mm \ Hg$. The mole fraction of the solute in the solution is $0.2$. If the vapor pressure is to be decreased by $20 \ mm \ Hg$,what will be the mole fraction of the solvent?

If $f(x) = \frac{1}{\sqrt{x + 2 \sqrt{2x - 4}}} + \frac{1}{\sqrt{x - 2 \sqrt{2x - 4}}}$ for $x > 2$,then $f(11)$ is equal to

Which of the following is an acidic salt?

Identify $A$ and $B$ in the following reaction:
$C_2H_5Cl \xrightarrow{A} C_2H_5OH \xleftarrow{B} C_2H_5Cl$

If the radius of a star is $R$ and it acts as a black body,what would be the temperature of the star,in which the rate of energy production is $Q$? ( $\sigma$ stands for Stefan's constant.)