Equal weights of ethane and hydrogen are mixed in an empty container at $25^{\circ} C$. The fraction of total pressure exerted by hydrogen is

The number of chlorine atoms in $20 \, mL$ of chlorine gas at $STP$ is ..... $\times 10^{21}$. (Round off to the Nearest Integer).
[Assume chlorine is an ideal gas at $STP$,$R = 0.083 \, L \, bar \, mol^{-1} \, K^{-1}$,$N_{A} = 6.023 \times 10^{23}$]

Based on the equation $C_6H_{6(l)} + \frac{15}{2} O_{2(g)} \rightarrow 6CO_{2(g)} + 3H_2O_{(l)}$,the enthalpy change is $\Delta H = -3264.4 \, kJ \, mol^{-1}$. How much energy in $kJ$ is released when $7.8 \, g$ of benzene is burned in air?

Concentrated nitric acid is labelled as $75 \%$ by mass. The volume in $mL$ of the solution which contains $30 \ g$ of nitric acid is $.............$ Given : Density of nitric acid solution is $1.25 \ g / mL$

How many millilitres of $6.0 \ M$ hydrochloric acid should be used to prepare $150 \ mL$ of a solution which is $0.30 \ M$ in hydrogen ion?

$4.0 \ g$ of a mixture containing $Na_2CO_3$ and $NaHCO_3$ is heated to $673 \ K$. The loss in mass of the mixture is found to be $0.62 \ g$. The percentage of sodium carbonate in the mixture is: