$10 \, mL$ of concentrated $H_2SO_4$ $(18 \, M)$ is diluted to $1 \, L$. The approximate strength of the dilute acid is.....$N$

Which one of the following is the lightest?

$H_2O_2$ solution used for hair bleaching is sold as a solution of approximately $5.0 \, g$ $H_2O_2$ per $100 \, mL$ of the solution. The molecular mass of $H_2O_2$ is $34$. The molarity of this solution is approximately $........$ $M$.

$20 \ mL$ of $2 \ M$ $NaOH$ solution is added to $400 \ mL$ of $0.5 \ M$ $NaOH$ solution. The final concentration of the solution is $.......... \times 10^{-2} \ M$. $(Nearest \ integer)$.

The ratio of the number of water molecules in Mohr's salt and potash alum is $.... \times 10^{-1}$.

$100 \ g$ of a mixture of $NaOH$ and $Na_2SO_4$ is neutralized by $100 \ mL$ of $0.5 \ M \ H_2SO_4$. What is the amount of $Na_2SO_4$ present in the mixture (in $g$)?