JEE MAIN - Chemistry (2013 (Offline) - No. 2)
How many litres of water must be added to 1 litre of an aqueous solution of HCl with a pH of 1 to create an
aqueous solution with pH of 2?
0.1 L
0.9 L
2.0 L
9.0 L
Explanation
As $$\,\,\,pH = 1;\,\,{H^ + } = {10^{ - 1}} = 0.1\,M$$
$$\,\,\,pH = 2;\,\,{H^ + } = {10^{ - 2}} = 0.01\,M$$
$$\therefore$$ $$\,\,\,{M_1} = 0.1\,\,{V_1} = 1;\,\,$$
$${M_2} = 0.01\,\,{V_2} = ?$$
From
$${M_1}{V_1} = {M_2}{V_2};0.1 \times 1 = 0.01 \times {V_2}$$
$${V_2} = 10\,$$ litre
$$\therefore$$ volume of water added $$ = 10 - 1 = 9\,$$ litre.
$$\,\,\,pH = 2;\,\,{H^ + } = {10^{ - 2}} = 0.01\,M$$
$$\therefore$$ $$\,\,\,{M_1} = 0.1\,\,{V_1} = 1;\,\,$$
$${M_2} = 0.01\,\,{V_2} = ?$$
From
$${M_1}{V_1} = {M_2}{V_2};0.1 \times 1 = 0.01 \times {V_2}$$
$${V_2} = 10\,$$ litre
$$\therefore$$ volume of water added $$ = 10 - 1 = 9\,$$ litre.
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