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NEET Chemistry Solutions / विलयन Question Bank Self Evaluation Test - Solutions

  • question_answer
    If sodium sulphate is considered to be completely dissociated into cations and anions in aqueous solution, the change in freezing point of water \[\left( \Delta {{T}_{f}} \right),\] when 0.01 mol of sodium sulphate is dissolved in 1 kg of water, is \[\left( {{K}_{f}}=1.86K\text{ }kg\text{ }mo{{l}^{-1}} \right)\]

    A) 0.372 K            

    B) 0.0558 K

    C) 0.0744 K           

    D) 0.0186 K

    Correct Answer: B

    Solution :

    [b] Sodium sulphate dissociates as \[N{{a}_{2}}S{{O}_{4}}\left( s \right)\xrightarrow{{}}2N{{a}^{+}}+SO{{_{4}^{-}}^{-}}\] hence van't hoff factor i = 3 Now \[\Delta {{T}_{f}}=i{{k}_{f}}.m\] \[=3\times 1.86\times 0.01=0.0558\text{ }K\]


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