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NEET Sample Paper NEET Sample Test Paper-70

  • question_answer
    Specific rotation of sugar solution is 0.01 SI units. \[200\text{ }kg\text{ }{{m}^{-}}^{3}\]of impure sugar solution is taken in a polarimeter tube of length 0.25 m and an optical rotation of 0.4 rad is observed. The percentage of purity of sugar in the sample is-

    A) \[11%\]           

    B) \[20%\]

    C) \[80%\]           

    D) \[89%\]

    Correct Answer: C

    Solution :

    Specific rotation of sugar solution is \[\alpha =\frac{angle\,\,of\,\,rotation}{length\,\,of\,\,tube\times concentration}\] \[=\,\,\,\frac{\theta }{l\times C}\] \[\therefore \,\,\,\,\,\,\,\,\,C=\frac{\theta }{l\alpha }\] \[=\,\,\,\frac{0.4}{0.25\times 0.01}\,\,=\,\,160\,\,kg/{{m}^{3}}\] Thus, purity of sugar solution \[=\,\,\,\frac{160}{200}\,\,=\,\,100\,\,=\,\,80%\]


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