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KVPY Sample Paper KVPY Stream-SX Model Paper-31

  • question_answer
    What is the pH of a saturated solution of \[Cu{{(OH)}_{2}}?\] \[(Ksp=2.6\times {{10}^{-19}})\]

    A) 6.1

    B) 7.30

    C) 8.42     

    D) 7.90

    Correct Answer: C

    Solution :

    \[Cu\,\,{{(OH)}_{2}}(s)\,\,\rightleftharpoons \,\,C{{\underset{S}{\mathop{u}}\,}^{2+}}(aq.)+\underset{2S}{\mathop{2O}}\,\,{{H}^{-}}(aq.)\]
    \[{{K}_{sp}}=4\,\,{{S}^{3}}\]
    \[\therefore \,\,S=4\times {{10}^{-7}}\]
    \[[O{{H}^{-}}]=2\,\,S=8\times {{10}^{-7}}\]
    \[pOH=6.1\]      \[\therefore pH=7.90\]


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