Redox Reactions Ques 19
19. Oxidation numbers of $P$ in $PO_4^{3-}$, of $S$ in $SO_4^{2-}$ and that of $Cr$ in $Cr_2 O_7^{2-}$ are respectively
[2009]
(a) $+3,+6$ and +5
(b) $+5,+3$ and +6
(c) $-3,+6$ and +6
(d) $+5,+6$ and +6
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Solution:
- (d) $PO_4^{3-}=x+4(-2)=-3 ; x-8=-3 ; x=+5$
$SO_4^{2-}=x+4(-2)=-2 ; x-8=-2 ; x=+6$
$Cr_2 O_7^{2-}=2 x+7(-2)=-2 ; 2 x-14=-2$;
$ 2 x=12 ; x=+6 $
BETA
