Calculate the emf of the following cell: Pt(H21atm)|CH3CH2COH(0.15M)||0.01MNH4OH|H2(1atm)Pt Ka for CH3CH2COOH=1.4×10−5 Kb for NH4OH1.8×10−5.
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Solution
[H+] in CH3CH2COOH=√C×Ka=√0.15×1.4×10−5 =1.449×10−3 [OH−] in NH4OH=√C×Kb=√0.01×1.8×10−5=0.4242×10−3 [H+] in NH4OH=10−140.4242×10−3=2.3573×10−11 Ecell=0.0591log[H+]RHS[H+]LHS −0.4603volt.