Question

An iodised salt contain $0.5$% of $NaI$. A person consumes $3\text{g}$ of salt everyday. The number of iodide ions going into his body everyday is:
[Atomic wt. of Iodine = $127u$]

• A. ${10}^{-4}$
• B. $6.02\times {10}^{-4}$
• C. $7.11\times {10}^{19}$
• D. $6.02\times {10}^{23}$

Answer 1

The correct option is C $7.11\times {10}^{19}$

$3\text{g}$ of salt corresponds to $3\times \frac{0.5}{100}=0.015\text{g}$ of $NaI$
or
$\frac{0.015}{127+23}=1.0\times {10}^{-4}\text{moles of}NaI$.

$\Rightarrow \text{Moles of Iodide ions}=\frac{0.015}{127}=1.18\times {10}^{-4}$

The number of iodide ions going into his body everyday is $1.18\times {10}^{-4}\times 6.023\times {10}^{23}=7.11\times {10}^{19}$.