CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2011

  • question_answer
    0.023 g of sodium metal is reacted with\[100\text{ }c{{m}^{3}}\] of water. The pH of the resulting solution is

    A)  10                                         

    B)  8

    C)  9                                            

    D)  12

    Correct Answer: D

    Solution :

    \[2Na+2{{H}_{2}}O\xrightarrow{{}}2NaOH+{{H}_{2}}\] \[\underset{0.023}{\mathop{(2\times 23=46)}}\,\]                          \[\underset{0.04}{\mathop{(2\times 40=80)}}\,\] \[\therefore \]  \[[O{{H}^{-}}]=\frac{0.04}{40}\times 10={{10}^{-2}}\] \[\because \]     \[pOH=-\log \,\,[O{{H}^{-}}]\]                 \[pOH=2\] \[\because \]     \[pH+pOH=14\]                 \[pH=14-pOH\]                 \[pH=14-2\]                 \[pOH=12\]


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