Question

Assertion : The correct order of oxidising power is : $V{O}_2^{+}$ $<C{r}_2{O}_7^{2-}<Mn{O}_4^{-}$
Reason : The oxidation state of $Mn$ is $+7$.

• A. If both assertion and reason are true and reason is the correct explanation of assertion
• B. If both assertion and reason are true but reason is not the correct explanation of assertion
• C. If assertion is true but reason is false
• D. If both assertion and reason are false

Answer 1

Answer: (B)

The oxidation states of the given compounds are
VO${}_2^{+}$ : x + 2(-2) = +1
$\Rightarrow$ x = +5
Cr₂O${}_7^{2-}$ : 2x + 7(-2) = -2
$\Rightarrow$ 2x = +12
$\Rightarrow$ x = +6
MnO${}_4^{-}$ : x + 4(-2) = -1
x = -1 + 8 = + 7
The correct order of oxidising power is
VO${}_2^{+}$ < Cr₂O${}_7^{2-}$ < MnO${}_4^{-}$
due to the increasing stability of the lower species to which they are reduced.