Mole fraction of $O_2$ in $O_2$ and $O_3$ mixture is $0.25$. Hence percentage concentration $\left( \frac{w}{W} \% \right)$ of $O_2$ in the mixture is:

An aqueous solution of $6.3 \ g$ oxalic acid dihydrate is made up to $250 \ mL$. The volume of $0.1 \ N \ NaOH$ required to completely neutralize $10 \ mL$ of this solution is $...... \ mL$.

When a jar containing a gaseous mixture of equal volumes of $CO_2$ and $H_2$ is placed in a solution of sodium hydroxide,the solution level will:

What is the percentage of lead in a lead pencil (in $\%$)?

$A$ mixture of sodium oxide $(Na_2O)$ and calcium oxide $(CaO)$ is dissolved in water and saturated with excess carbon dioxide $(CO_2)$ gas. The resulting solution is $......$ It contains $.........$ :

When $400 \ mL$ of $0.2 \ M \ H_2SO_4$ is mixed with $600 \ mL$ of $0.1 \ M \ NaOH$, the heat evolved is $3.43 \ kJ$. If the specific heat of water is $4.18 \ J \ K^{-1} \ g^{-1}$, the rise in temperature of the final solution will be ........... $K$. (Assume the specific heat capacity of the final solution is the same as that of water)