$A$ solution of sodium sulphate contains $92 \ g$ of $Na^{+}$ ions per kilogram of water. The molality of $Na^{+}$ ions in that solution in $mol \ kg^{-1}$ is:

When an object is placed at a distance of $25 \, cm$ from a concave mirror,the magnification is $m_1$. The object is moved $15 \, cm$ farther away with respect to the earlier position,and the magnification becomes $m_2$. If $m_1/m_2 = 4$,the focal length of the mirror is $..... \, cm$ (Assume image is real,$m_1$ and $m_2$ are numerical values).

For the reaction $C_{(s)} + CO_{2_{(g)}} \rightleftharpoons 2CO_{(g)}$,the partial pressures of $CO_2$ and $CO$ are $2.0 \ atm$ and $4.0 \ atm$ respectively at equilibrium. The $K_p$ for the reaction is

How is red phosphorus obtained from white phosphorus?

If $\alpha$ and $\beta$ are the roots of $x^2-2x+4=0$,then the value of $\alpha^6+\beta^6$ is

If $\frac{d^2y}{dx^2} = 0$,then