If $10$ volumes of dihydrogen gas reacts with $5$ volumes of dioxygen gas,how many volumes of water vapour would be produced?

Heat energy is incident on the surface at the rate of $1000 ~J/min$. If the coefficient of absorption is $0.8$ and the coefficient of reflection is $0.1$,then the heat energy transmitted by the surface in $5 ~min$ is: (in $~J$)

If $z = \sec(y - ax) + \tan(y + ax)$,then $\frac{\partial^2 z}{\partial x^2} - a^2 \frac{\partial^2 z}{\partial y^2} = $

Vitamin $K$ is required for:

$A$ coordination complex contains $Co^{3+}$,$Cl^{-}$,and $NH_3$. When dissolved in water,one mole of this complex gives a total of $3$ moles of ions. The complex is

$A$ bag contains $6$ white and $4$ black balls. Two balls are drawn at random. The probability that they are of the same colour is: