NEET UG 2008 — Chemistry Organic Chemistry

Key Idea : The reagent which is present in smaller quantity is called the limiting reagent and the moles of product depends on it and number of moles $=\frac{\text { weight }}{\text { molecular weight }}$= molecular weight  weight ​ $$\begin{array}{ccc} \mathrm{PbO} & 2 \mathrm{HCl} \longrightarrow & \mathrm{PbCl}_2+\mathrm{H}_2 \mathrm{O} \\ 207.2+16 & 2(35.5+1) & 207.2+71 \\ =223.2 & =73 & =278.2 \end{array}$$PbO207.2+16=223.2​2HCl⟶2(35.5+1)=73​PbCl2​+H2​O207.2+71=278.2​ Here, 1 mole of $\mathrm{PbO}$PbO reacts with 2 moles of $\mathrm{HCl}$HCl, thus $\mathrm{PbO}$PbO is the limiting reagent $\because 223.2 \mathrm{~g}$∵223.2 g PbO gives $\mathrm{PbCl}_2=278.2 \mathrm{~g}$PbCl2​=278.2 g $\therefore 6.5 \mathrm{~g} \mathrm{PbO}$∴6.5 gPbO will give $\mathrm{PbCl}_2$PbCl2​ $$\begin{aligned} & =\frac{278.2}{223.2} \times 6.5 \mathrm{~g} \\ & =\frac{278.2 \times 6.5}{223.2 \times 278.2} \mathrm{~mol} \\ & =0.029 \mathrm{~mol} \end{aligned}$$​=223.2278.2​×6.5 g=223.2×278.2278.2×6.5​ mol=0.029 mol​