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 $\%$)

How much $MgO$ is produced from $1.2 \ g$ of $Mg$ (atomic mass $= 24$)?

For the reaction $2Al_{(s)} + 6HCl_{(aq)} \rightarrow 2Al^{3+}_{(aq)} + 6Cl^{-}_{(aq)} + 3H_{2_{(g)}}$,which of the following statements is correct?

Calcium carbonate reacts with aqueous $HCl$ to give $CaCl_{2}$ and $CO_{2}$ according to the reaction,
$CaCO_{3(s)} + 2HCl_{(aq)} \rightarrow CaCl_{2(aq)} + CO_{2(g)} + H_{2}O_{(l)}$
What mass of $CaCO_{3}$ is required to react completely with $25 \ mL$ of $0.75 \ M$ $HCl$ (in $g$)?

$A$ pre-weighed vessel is filled with $O_2$ and weighed at $STP$. It is then evacuated and filled with $SO_2$ gas at the same temperature and pressure,and weighed again. The weight of $O_2$ will be:

If Avogadro's number is $A_0$,the number of sulphur atoms present in $200 \, mL$ of $1 \, N \, H_2SO_4$ is