RAJASTHAN PMT Rajasthan - PMT Solved Paper-2008

  • question_answer
    A steady current of 1.5 A flows through a copper voltameter for 10 min. If the electrochemical equivalent of copper is \[30\times {{10}^{-5}}\,g\,{{C}^{-1}},\] the mass of copper deposited on the electrode will be

    A)  0.40 g                                  

    B)  0.50 g

    C)  0.67 g                  

    D)         0.27 g

    Correct Answer: D

    Solution :

    Key Idea Apply first law of electrolysis during deposition of charge on an electrode through electrolysis. If \[m\] is the mass of a substance deposited or liberated at an electrode during electrolysis when a charge q passes through electrolyte, then according to Faradays first law of electrolysis,                 \[m\propto q\] or            \[m=zq\] where \[z\] is a constant of proportionality and is called electrochemical equivalent (ECE) of the substance. If an electric current \[I\] flows through the electrolyte, then                 \[q=It\]                 \[m=zit\]             Here,\[i=1.5\,\,A,\,\,t=10\min =10\times 60s\],                 \[z=30\times {{10}^{-5}}g\,\,{{C}^{-1}}\] Hence, mass of copper deposited on the electrode                 \[m=30\times {{10}^{-5}}\times 1.5\times 10\times 60\]                     \[=27\times {{10}^{-2}}=0.27\,\,g\]


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