$x$ grams of calcium carbonate was completely burnt in air. The weight of the solid residue formed is $28 \,g$. What is the value of $x$ (in grams)?

In the reaction,$2Al_{(s)} + 6HCl_{(aq)} \rightarrow 2Al^{3+}_{(aq)} + 6Cl^{-}_{(aq)} + 3H_{2(g)}$

For the gaseous reaction $H_2 + Cl_2 \rightarrow 2HCl$,if $40 \ mL$ of hydrogen reacts with chlorine,the volume of chlorine required and the volume of $HCl$ formed are respectively:

$9.3 \ g$ of aniline is subjected to reaction with excess of acetic anhydride to prepare acetanilide. The mass of acetanilide produced if the reaction is $100 \%$ completed is $x \times 10^{-1} \ g$. Find the value of $x$. (Given molar mass in $g \ mol^{-1}: N: 14, O: 16, C: 12, H: 1$)

How many grams of $NaOH$ are equivalent to $100 \, mL$ of $0.1 \, N$ oxalic acid?

$4.0 \,g$ of $NaOH$ are contained in one decilitre of solution. Its molarity would be ......... $M$.