Question
What will be the molality of chloroform in the water sample which contains $$15\,ppm$$ chloroform by mass ?
A.
$$1.25 \times {10^{ - 4}}m$$
B.
$$2.5 \times {10^{ - 4}}m$$
C.
$$1.5 \times {10^{ - 3}}m$$
D.
$$1.25 \times {10^{ - 5}}m$$
Answer :
$$1.25 \times {10^{ - 4}}m$$
Solution :
$$\eqalign{
& 15\,ppm = \frac{{15}}{{{{10}^6}}} \times {10^2} \cr
& \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 1.5 \times {10^{ - 3}}g \cr
& {\text{Molality of}}\,\,CHC{l_3}\,\,{\text{solution}} \cr
& = \frac{{1.5 \times {{10}^{ - 3}}}}{{100}} \times \frac{{1000}}{{119.5}} \cr
& = 1.25 \times {10^{ - 4}}m \cr} $$