JEE MAIN - Chemistry (2023 - 30th January Morning Shift - No. 14)
Some amount of dichloromethane $$\left(\mathrm{CH}_{2} \mathrm{Cl}_{2}\right)$$ is added to $$671.141 \mathrm{~mL}$$ of chloroform $$\left(\mathrm{CHCl}_{3}\right)$$ to prepare $$2.6 \times 10^{-3} \mathrm{M}$$ solution of $$\mathrm{CH}_{2} \mathrm{Cl}_{2}(\mathrm{DCM})$$. The concentration of $$\mathrm{DCM}$$ is ___________ ppm (by mass).
Given :
atomic mass : C = 12
H = 1
Cl = 35.5
density of $$\mathrm{CHCl}_{3}=1.49 \mathrm{~g} \mathrm{~cm}^{-3}$$
Explanation
Mass of $$\mathrm{CHCl_3=671.141\times1.49=1000}$$ gm
$$2.6 \times {10^{ - 3}} = {{moles\,of\,C{H_2}C{l_2}} \over {0.671141}}$$
$$\Rightarrow$$ moles of $$C{H_2}C{l_2} = 1.74496 \times {10^{ - 3}}$$
mass of $$C{H_2}C{l_2} = 148.32 \times {10^{ - 3}}$$ gm
Composition of $$C{H_2}C{l_2} = {{148.32 \times {{10}^{ - 3}}} \over {1000}} \times {10^6}$$
= 148.32 ppm
$$\approx$$ 148
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