The amount of $50\% \ (w/w)$ solution of hydrochloric acid required to react with $200 \ g$ of $CaCO_3$ would be (in $g$)

$19 \ g$ of a mixture containing $NaHCO_3$ and $Na_2CO_3$ on complete heating liberated $1.12 \ L$ of $CO_2$ at $STP$. The weight of the remaining solid was $15.9 \ g$. What is the weight (in $g$) of $Na_2CO_3$ in the mixture before heating?

$C_2H_4$ can react with $H_2$ in the presence of a catalyst to form $C_2H_6$ as per the following reaction: $C_2H_{4(g)} + H_{2(g)} \xrightarrow{\text{Catalyst}} C_2H_{6(g)}$. The amount of $C_2H_4$ in grams required to produce $50 \ g$ of $C_2H_6$ is: (in $g$)

What is the number of moles of water removed from one mole of cane sugar when charred completely using conc. $H_2SO_4$?

How many moles of $H_2O_2$ are required to decolorize $1$ mole of $KMnO_4$ (in $.5$)?

How many moles of ferric alum $(NH_4)_2SO_4 \cdot Fe_2(SO_4)_3 \cdot 24H_2O$ can be made from a sample of $Fe$ containing $0.0056 \ g$ of it?