NEET Chemistry NEET PYQ-Solutions

  • 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:            [AIPMT 1998]

    A) 34.2

    B) 171.2

    C) 68.4

    D) 136.8

    Correct Answer: C

    Solution :

    [c] 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