Question

Ferrous sulphate heptahydrate is used to fortify foods with iron.The amount (in grams) of the salt required to achieve 10 ppm of iron in 100 kg of wheat (Rounded-off to the nearest integer) is
[Atomic weight : Fe=55.85 S=32.00 O=16.00]

Answer 1

$10ppm=\frac{\text{Mass of Fe(in g)}}{100\times 1000}\times {10}^6$
$\text{Mass of}Fe=1g$
$\text{Molar mass of}FeS{O}_4.7H_{2}O=278gmo{l}^{-1}$
Mass of $Fe$ is 56 g in 1 mol
i.e.
$1g\text{in}\frac{1}{56}mol$.
The amount (in grams) of the salt required to achieve 10 ppm of iron in 100 kg of wheat
$\Rightarrow \frac{1}{56}\times 278=4.96g\approx 5g$