question_answer

A litre of water was evaporated from 8L of salt solution containing 8% salt. The percentage of salt left in the remaining solution is

A)  \[7\frac{1}{7}%\]                                 

B)  \[7\frac{1}{9}%\]          

C)  \[9\frac{1}{7}%\]

D)  \[7\frac{1}{3}%\]

Correct Answer: C

Solution :

(c): % age means \[\frac{\text{weight}}{\text{volume}}%\text{ }age\Rightarrow \] in 100 ml, Salt being non-volatile, will not evaporate In 81, we have \[8000ml\Rightarrow \frac{8}{100}\times 8000\]gm salt = 640 gm salt. After evaporation 7L solution is left with same 640 gm salt \[=\frac{W}{V}%=\frac{640\,gm}{7000\,mL}\times 100%=9\frac{1}{7}%\].