• question_answer
                    A 5% solution of cane sugar (mol. wt. = 342) is isotonic with 1% solution of a substance X. The molecular weight of X is:                                                                                                                                  

    A)                 34.2         

    B)                            171.2

    C)                                            68.4       

    D)                                            136.8

    Correct Answer: C

    Solution :

                    Isotonic solutions are the solutions having same osmotic pressure.                 Applying Van't Hoff equation                 \[\pi V=nST\]                 \[\pi =cST\]                                         Osmotic pressure of 5% cane sugar solution                 \[({{\pi }_{1}})\,C\times S\times T=\frac{50\,g/L}{342}\times 0.0821\times T\]                 Osmotic pressure of 1% solution of substance \[x\,({{\pi }_{2}})\]                 \[=\frac{10g/L}{M}\times 0.0821\times T\]                 Both are isotonic                 So,          \[{{\pi }_{1}}={{\pi }_{2}}\]                 or            \[\frac{50}{342}\times 0.0821\times T=\frac{10}{M}\times 0.0821\times T\]                 \[\therefore M\,(mol.\,wt.\,of\,X)=\frac{342}{5}=68.4\]

You need to login to perform this action.
You will be redirected in 3 sec spinner