First find the oxidation states of the various atoms: <span>in Cr2O2 2- Cr @ +1; In NH3 N @ +3; in CrO3 Cr @ +3, N2 N @ 0 </span> <span>Note that N gained electrons, ie, was reduced; Cr was oxidized </span> <span>Now there is a problem, because B has NH4+ which the problem did not, and is not balanced, showing e- in/out </span> <span>B.NH4+ → N2 </span>
<span>Which of the following is an oxidation half-reaction? </span> <span>A.Sn 2+ →Sn 4+ + 2e- </span> <span>Sn lost electrons so it got oxidized</span>
