CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2008

  • question_answer
    The pH of a solution obtained by mixing 50 mL of\[1\text{ }N\text{ }HCl\]and 30 mL of\[1\text{ }N\text{ }NaOH\]is [log 2.5 = 0.3979]

    A) 3.979                    

    B)        0.6021

    C) 12.042                  

    D)        1.2042

    E)  0.3979

    Correct Answer: B

    Solution :

    Concentration of mixture \[cone\text{ }of\text{ }acid\times its\text{ }volume\] \[=\frac{-\,cone\text{ }of\text{ }base\times its\text{ }volume}{Total\text{ }volume}\] \[N=\frac{{{N}_{1}}{{V}_{1}}-{{N}_{2}}{{V}_{2}}}{{{V}_{1}}+{{V}_{2}}}\]                 \[=\frac{50\times 1-30\times 1}{50+30}\]                 \[=\frac{20}{80}\]                 \[=\frac{1}{4}\] \[=0.25\] Since\[HCl\]is in excess, so mixture is acidic and mixture contains \[[{{H}^{+}}]\]ion. Thus,                 \[[{{H}^{+}}]=0.25\]                 \[pH=-\log [{{H}^{+}}]\] \[=-log\text{ }0.25\] \[=0.6021\]


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