Which balanced equation represents a redox
reaction?
(1) pcl5 ==> pcl3 + cl2
(2) koh + hcl ==> kcl + h=o
(3) libr==> li+ + br=
(4) ca2+ + so42- ==> caso4

(1) PCl5 ==> PCl3 + Cl2

Explanation: PCl5 == PCl3 + Cl2 is a redox reaction. In a redox reaction, there will be a change in oxidation number for two elements. The oxidation number of the P is +5 in Pcl5 and it is +3 in PCl3, so the P is reduced. The Cl has an oxidation number of -1 in PCl5, but as a free elements in Cl2 it has an oxidation number of zero, so it is oxidized. Always look for free elements to help identify redox reactions.

catya that's not even a b or c

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