NCERT Class XII Chemistry
Chapter - Electrochemistry
Questions with Solutions
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Question : 4
Total: 32
Calculate the standard cell potentials of galvanic cell in which the following reactions take place:
(i)2 C r ( s ) + 3 C d 2 + ( a q ) → 2 C r 3 + ( a q ) + 3 C d ( s )
(ii)F e 2 + ( a q ) + A g + ( a q ) → F e 3 + ( a q ) + A g ( s )
Calculate theΔ r G °
Given :E ° C r 3 + ∕ C r = − 0.74 V , E ° C d 2 + ∕ C d = − 0.40 V
E ° A g + ∕ A g = 0.80 V , E ° F e 3 + ∕ F e 2 + = 0.77 V
(i)
(ii)
Calculate the
Given :
Solution:
(i) E ° cell = E ° cathode − E ° anode = − 0.40 V − ( − 0.74 V ) = + 0.34 V
Δ G ° = − n F E ° cell = − 6 × 96500 × 0.34 = − 196860 J mol − 1 = − 196.86 k J mol − 1
− Δ G ° = 2.303 R T log K
196860 = 2.303 × 8.314 × 298 × l o g K l o g K = 34.5014
K = Antilog 34.5014 = 3.172 × 10 34
(ii) E°c e l l
ΔG° = –nFE°c e l l mol – 1 mol – 1
ΔG°= –2.303 RT log K
–2895 = –2.303 × 8.314 × 298 × log K
or log K = 0.5074
K = Antilog (0.5074) = 3.22
(ii) E°
ΔG° = –nFE°
ΔG°= –2.303 RT log K
–2895 = –2.303 × 8.314 × 298 × log K
or log K = 0.5074
K = Antilog (0.5074) = 3.22
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