E⊖ values of some redox couples are given below. On the basis of these values choose the coorect option.
E⊖ values :
Br2Br−=+1.90Ag+Ag(s)=+0.80Cu2+Cu(s)=+0.34I2(S)I−=+0.54;
(a) Cu will reduce Br−
(b) Cu will reduce Ag
(c) Cu will reduce I−
(d) Cu will reduce Br2
Given that E⊖ values of
Br2Br−=+1.90VAg+Ag(S)=+0.80VCu2+Cu(s)=+0.34VI2(S)I−=+0.54VBr−Br2=+1.90V
The E⊖ values show that copper will reduce Br2, if the E⊖ of the following redox reaction is positive.
Now
2Cu+Br2→CuBr2Cu→Cu2++2e−;E⊖=−0.34VBr2+2e−→2Br−;E=+1.09VCu+Br2→CuBr2;E⊖=+0.75V
Since E⊖ of this reaction is positive. therefore, Cu can reduce Br2 while other reaction will give negative value.
Answer: (d). Cu will reduce Br2