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Bleaching powder and bleach solution are produced on a large scale and used in several household products. The effectiveness of bleach solution is often measured by iodometry.
Question: $25 \mathrm{~mL}$ of household solution was mixed with $30 \mathrm{~mL}$ of $0.50$ M KI and $10 \mathrm{~mL}$ of $4 \mathrm{~N}$ acetic acid. In the titration of the liberated iodine, $48 \mathrm{~mL}$ of $0.25 \mathrm{~N~} \mathrm{Na}_{2} \mathrm{~S}_{2} \mathrm{O}_{3}$ was used to reach the end point. The molarity of the household bleach solution is
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Question: $25 \mathrm{~mL}$ of household solution was mixed with $30 \mathrm{~mL}$ of $0.50$ M KI and $10 \mathrm{~mL}$ of $4 \mathrm{~N}$ acetic acid. In the titration of the liberated iodine, $48 \mathrm{~mL}$ of $0.25 \mathrm{~N~} \mathrm{Na}_{2} \mathrm{~S}_{2} \mathrm{O}_{3}$ was used to reach the end point. The molarity of the household bleach solution is
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$0.24 \mathrm{M}$
Bleach $+2 \mathrm{KI} \longrightarrow \mathrm{I}_{2}+$ Products
$\mathrm{I}_{2}+2 \mathrm{Na}_{2} \mathrm{~S}_{2} \mathrm{O}_{3} \longrightarrow \mathrm{Na}_{2} \mathrm{~S}_{4} \mathrm{O}_{6}+2 \mathrm{NaI}$
Number of millimole of hypo $=0.25 \times 48$
$=2 \times$ millimole of $\mathrm{I}_{2}$
$\therefore$ Number of millimole of $\mathrm{I}_{2}=\frac{0.25 \times 48}{2}=6$
millimole of $\mathrm{I}_{2}=$ millimole of bleach
Molarity of bleaching solution
$=\frac{\text { Millimoles of bleach }}{\text { Vol.(in } \mathrm{mL} \text { ) of bleach }}=\frac{6}{25}=0.24$
$\mathrm{I}_{2}+2 \mathrm{Na}_{2} \mathrm{~S}_{2} \mathrm{O}_{3} \longrightarrow \mathrm{Na}_{2} \mathrm{~S}_{4} \mathrm{O}_{6}+2 \mathrm{NaI}$
Number of millimole of hypo $=0.25 \times 48$
$=2 \times$ millimole of $\mathrm{I}_{2}$
$\therefore$ Number of millimole of $\mathrm{I}_{2}=\frac{0.25 \times 48}{2}=6$
millimole of $\mathrm{I}_{2}=$ millimole of bleach
Molarity of bleaching solution
$=\frac{\text { Millimoles of bleach }}{\text { Vol.(in } \mathrm{mL} \text { ) of bleach }}=\frac{6}{25}=0.24$
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