Moles of conc. $HNO_3$ required to oxidise one mole of sulphur is :
$S + 6HNO_3 \rightarrow H_2SO_4 + 6NO_2 + 2H_2O$

In the balanced equation of the following reaction,the ratio of $a / b$ is: $aCaCO_3 + bH_3PO_4 \rightarrow pCa_3(PO_4)_2 + qCO_2 + rH_2O$

For the given reaction:
$CaCO_{3} + 2HCl \to CaCl_{2} + H_{2}O + CO_{2}$
If $90 \ g$ of $CaCO_{3}$ is added to $300 \ mL$ of $HCl$ solution which contains $38.55\%$ $HCl$ by mass and has a density of $1.13 \ g \ mL^{-1}$,then which of the following options is correct?
[Given molar masses of $H$,$Cl$,$Ca$,and $O$ are $1$,$35.5$,$40$,and $16 \ g \ mol^{-1}$ respectively]

How many moles of lead chloride will be produced by the reaction of $6.5 \ g$ of $PbO$ and $3.2 \ g$ of $HCl$?

Calculate the weight of $CaO$ formed in quintals when $10 \ g$ of $CaCO_3$ is heated with $4.4 \ g$ of $CO_2$.

Calculate the mass of $AgCl$ precipitated when $25 \ mL$ of $35 \%$ solution of $AgNO_3$ and $25 \ mL$ of $11.6 \%$ solution of $NaCl$ are mixed. (in $g$)