question_answer

Calculate the potential of the following half-cells Given:

A) \[-0.907V\]            

B)        \[0.907V\]    

C) \[-0.313\]               

D)       \[0.313\]

Correct Answer: B

Solution :

     [b] \[(pH=9.0,\,pOH=14-9=5,\,\overset{\bigcirc -}{\mathop{O}}\,H={{10}^{-5}}M\] Activity of \[{{H}_{2}}O=1\])             \[-\frac{0.06}{6}\log \frac{5.0\times {{10}^{-3}}\times {{({{10}^{-5}}M)}^{6}}}{2.5\times {{10}^{-3}}M}\] \[=0.61V-0.01\,(\log 2\times {{10}^{-30}})\] \[=0.61V-0.01(0.3-30)\]  \[(\log 2\,\,\approx \,\,0.3)\] \[=0.61\,V-0.01\times (-29.7)\] \[=0.61V+0.297\approx 0.907V\]