JEE MAIN - Chemistry (2020 - 7th January Evening Slot - No. 17)
The flocculation value of HCl for arsenic sulphide sol.
is 30 m mol L-1 If H2SO4 is used for the flocculatiopn of arsenic sulphide, the amount in grams, of H2SO4 in 250 ml required for the above purposed is ______.
(molecular mass of H2SO4 = 98 g/mol)
is 30 m mol L-1 If H2SO4 is used for the flocculatiopn of arsenic sulphide, the amount in grams, of H2SO4 in 250 ml required for the above purposed is ______.
(molecular mass of H2SO4 = 98 g/mol)
Answer
0.36to0.38
Explanation
Arsenic sulphide sol is negatively charged, so for flocculation
positive ion required. Here positive ion H+ present.
for 1 L, 30 mm moles of H+ is required
for 250 ml, $${{30} \over 4}$$ mm moles H+ is required
$$ \therefore $$ for 250 ml, $${{30} \over {4 \times 2}}$$ mm moles H2SO4 is required.
$$ \therefore $$ Weight of H2SO4 required = $${{30} \over {4 \times 2}} \times {10^{ - 3}} \times 98$$
= 0.3675 g
for 1 L, 30 mm moles of H+ is required
for 250 ml, $${{30} \over 4}$$ mm moles H+ is required
$$ \therefore $$ for 250 ml, $${{30} \over {4 \times 2}}$$ mm moles H2SO4 is required.
$$ \therefore $$ Weight of H2SO4 required = $${{30} \over {4 \times 2}} \times {10^{ - 3}} \times 98$$
= 0.3675 g
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