A and B are two substances undergoing radioactive decay in a container. The half life of A is 15 min and that of B is 5 min. If the initial concentration of B is 4 times that of A and they both start decaying at the same time, how much time will it take for the concentration of both of them to be same? _____________ min.

At $$25^{\circ} \mathrm{C}$$, the enthalpy of the following processes are given :

What would be the value of X for the following reaction ? _____________ (Nearest integer)

$$\mathrm{H_2O(g)\to H(g)+OH(g)~\Delta H^\circ=X~kJ~mol^{-1}}$$

Sum of oxidation states of bromine in bromic acid and perbromic acid is ___________.

Number of isomeric compounds with molecular formula $$\mathrm{C}_{9} \mathrm{H}_{10} \mathrm{O}$$ which (i) do not dissolve in $$\mathrm{NaOH}$$ (ii) do not dissolve in $$\mathrm{HCl}$$. (iii) do not give orange precipitate with 2,4-DNP (iv) on hydrogenation give identical compound with molecular formula $$\mathrm{C}_{9} \mathrm{H}_{12} \mathrm{O}$$ is ____________.