Chemistry - Redox Reactions Question with Solution | TestHub

$\mathrm{P}{\mathrm{b}}^{2+}$ + ${\mathrm{H}}_2\mathrm{S}$ $\to$ $\mathrm{PbS}$: 0.1 mol $\mathrm{P}{\mathrm{b}}^{2+}$ needs 0.1 mol ${\mathrm{H}}_2\mathrm{S}$. $2F{\mathrm{e}}^{3+}$ + $3{\mathrm{H}}_2\mathrm{S}$ $\to$ $\mathrm{F}{\mathrm{e}}_2{\mathrm{S}}_3$: 0.1 mol $\mathrm{F}{\mathrm{e}}^{3+}$ needs 0.15 mol ${\mathrm{H}}_2\mathrm{S}$. Ratio = 0.1 : 0.15 = 2:3, option (b).