Redox Reactions And Electrochemistry Ques 670
Question: How many electrons are involved in the following redox reaction-
$ Cr_2O_7^{2-}+F{{e}^{2+}}+C_2O_4^{2-}\to C{{r}^{3+}}+F{{e}^{3+}}+CO_2 $ (Unbalanced)
Options:
A) 3
B) 4
C) 6
D) 5
Show Answer
Answer:
Correct Answer: A
Solution:
[a] The reaction given is $ Cr_2O_7^{2-}+F{{e}^{2+}}+C_2O_2^{2-}\xrightarrow{{}}C{{r}^{3+}}+F{{e}^{3+}}+CO_2 $ $ Cr_2O_7^{2-}\xrightarrow{{}}2C{{r}^{3+}} $ On balancing $ 14{{H}^{+}}+Cr_2O_7^{2-}\xrightarrow{{}}2C{{r}^{3+}}+7H_2O $ …..(i) $ F{{e}^{2-}}\xrightarrow{{}}F{{e}^{3+}}+{{e}^{-}} $ ….(ii) $ C_2O_4^{2-}\xrightarrow{{}}2CO_2+2{{e}^{-}} $ …(iii) On adding all the three equations. $ Cr_2O_7^{2-}+F{{e}^{2+}}+C_2O_4^{2-}+14{{H}^{+}}+3{{e}^{-}} $ $ \xrightarrow{{}}2C{{r}^{3+}}+F{{e}^{3+}}+2CO_2+7H_2O $ Hence the total no. of electrons involved in the reaction = 3
