Which of the following pairs of substances cannot exist together in a solution?

If the harmonic mean between the roots of $(5+\sqrt{2}) x^2-b x+(8+2 \sqrt{5})=0$ is $4$,then the value of $b$ is

$A$ large open tank has two holes in the wall. One is a square hole of side $L$ at a depth $y$ from the top and the other is a circular hole of radius $R$ at a depth $4y$ from the top. When the tank is completely filled with water,the quantities of water flowing out per second from the two holes are the same. Then the value of $R$ is

What will be the $pH$ of an aqueous solution of $1.0 \ M$ ammonium formate? (Given: $pK_{a}=3.8$ and $pK_{b}=4.8$)

Name the blood cells,whose reduction in number can cause clotting disorder,leading to excessive loss of blood from the body.

In which of the following reactions,the concentration of product is higher than the concentration of reactant at equilibrium? $(K = \text{equilibrium constant})$