Question

One mole of acidified $ {{K}_{2}}C{{r}_{2}}{{O}_{7}} $ on reaction with excess $ KI $ will liberate ....... mole(s) of $ {{I}_{2}} $ :

• A. 6
• B. 1
• C. 7
• D. 2
• E. 3

Answer 1

Answer: (E)

$ C{{r}_{2}}O_{7}^{2-}+14{{H}^{+}}+6{{e}^{-}}\xrightarrow[{}]{{}}2C{{r}^{3+}}+7{{H}_{2}}O $ $ \begin{align} & \underline{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,(2{{I}^{-}}\xrightarrow{{}}{{I}_{2}}+2{{e}^{-}})\times 3} \\ & C{{r}_{2}}O_{7}^{2-}+14{{H}^{+}}+6{{I}^{-}}\xrightarrow{{}} \\ \end{align} $ $ 2C{{r}^{3+}}+7{{H}_{2}}O+3{{I}_{2}} $ Hence, number of moles of $ {{I}_{2}} $ produced = 3