Based on the reaction $CH_4 + 2O_2 \to CO_2 + 2H_2O$,calculate the number of moles of oxygen required to react with $4.8 \, g$ of methane.

The volumes of two $HCl$ solutions $A$ (Normality $= 0.5 \ N$) and $B$ (Normality $= 0.1 \ N$) to be mixed for preparing $2 \ L$ of $0.2 \ N \ HCl$ are:

If the concentration of compound $AB_5$ is $10^{-3} \text{ mol/L}$,then the concentration of $B^{-}$ will be .......

If a sample of $8.3 \ mL$ of $H_2SO_4$ $(36 \ N)$ is diluted with $991.7 \ mL$ of water,what is the approximate concentration of the resulting solution (in $N$)?

What mass in $g$ of hydrated oxalic acid $(H_2C_2O_4 \cdot 2H_2O)$ should be added for complete neutralization of $100 \ mL$ of $0.2 \ N \ NaOH$ solution?

If salicylic acid $(138 \text{ u})$ reacts with acetic anhydride $(102 \text{ u})$ to form aspirin $(180 \text{ u})$ and acetic acid $(60 \text{ u})$,calculate the percentage atom economy. (in $\%$)