Redox Reactions And Electrochemistry Ques 612
Question: A battery is constructed of Cr and $ Na_2Cr_2O_7 $ . The unbalanced chemical equation when such a battery discharges is following $ Na_2Cr_2O_7+Cr+{H^{+}}\to C{r^{3+}}+H_2O+N{a^{+}} $ If one Faraday of electricity is passed through the battery during the charging, the number of moles of $ C{r^{\text{3+}}} $ removed from the solution is
Options:
A) $ \frac{4}{3} $
B) $ \frac{1}{3} $
C) $ \frac{3}{3} $
D) $ \frac{2}{3} $
Show Answer
Answer:
Correct Answer: C
Solution:
[c] Reduction half reaction: $ Cr_2O_7^{2-}+6{e^{-}}~+14{H^{+}}\xrightarrow{{}}2C{r^{3+}}+7H_2O $ Oxidation half reaction: $ Cr\xrightarrow{{}}C{r^{3+}}+3{e^{-}} $ Overall reaction: $ Cr_2O_7^{2-}+Cr~+14{H^{+}}+3{e^{-}}\xrightarrow{{}}3C{r^{3+}}+7H_2O $ 3F of electricity = 3 moles of $ C{r^{3+}} $ 1F of electricity $ =\frac{3}{3} $ moles of $ C{r^{3+}} $
