A 1.85 g sample of an arsenic containing pes | vedclass

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(C) The balanced chemical equation for the reaction is: $3 Pb^{2+} + 2 AsO_4^{3-} \longrightarrow Pb_3(AsO_4)_2$. From the stoichiometry,$3 \ mol$ of

Vedclass · Accepted Answer

$5.4$

Vedclass · Answer

(C) The balanced chemical equation for the reaction is: $3 Pb^{2+} + 2 AsO_4^{3-} \longrightarrow Pb_3(AsO_4)_2$. From the stoichiometry,$3 \ mol$ of $Pb^{2+}$ reacts with $2 \ mol$ of $AsO_4^{3-}$. Therefore,$1 \ mol$ of $Pb^{2+}$ reacts with $\frac{2}{3} \ mol$ of $AsO_4^{3-}$. Number of moles of $Pb^{2+}$ used: $n_{Pb^{2+}} = Molarity 	imes Volume (L) = 0.1 	imes 0.020 = 2 	imes 10^{-3} \ mol$. Number of moles of $As$ present: $n_{As} = \frac{2}{3} 	imes 2 	imes 10^{-3} = 0.001333 \ mol$. Mass of $As$ in the sample: $W_{As} = n_{As} 	imes 	ext{atomic mass of } As = 0.001333 	imes 74.9 = 0.0998 \ g$. Mass percentage of $As$: $\% 	ext{ of } As = \frac{0.0998}{1.85} 	imes 100 \approx 5.395 \%$. Rounding to the nearest value,we get $5.4 \%$.

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