1. Which of the following chemical reactions is not a redox reaction?
QUESTION:
Which of the following chemical reactions is not a redox reaction?
C(s) + O2(g)  CO2(g)
Cl2(g) + 2 KBr(aq)  2 KCl(aq) + Br2(l)
2 KClO3(s)  2 KCl(s) + 3 O2(g)
NaOH(aq) + HCl(aq)  NaCl(aq) + H2O(l)
Redox is short of reduction-oxidation. It involves a transfer of electrons.
How to tell:
look for change in oxidation states
or look for elemental substance in reactant or product
Which of the following chemical reactions is not a redox reaction?
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The term redox is short for reduction-oxidation. The general procedure for
determining of a reaction is a redox reaction involves determining if there are changes in the oxidation states of
the atoms involved. However, in this particular question, three of the reactions
can be easily identified as redox reactions.
Any reaction that involves an elemental substance as a reactant or product is a redox reaction.
HIGHLIGHT “look for elemental substance in reactant or product”
By elemental substance, we mean an element that is not part of a compound.
Let’s examine the choices given here.
In choice A, we have two elemental substances involved as reactants... carbon
HIGHLIGHT C(s)
and oxygen
HIGHLIGHT O2(g)
So, the combination of carbon and oxygen to form carbon dioxide is a redox reaction.
A combination reaction involving at least one elemental substance is a redox reaction.
In choice B, we have one elemental substance involved as a reactant... chlorine
HIGHLIGHT Cl2(g)
and another elemental elemental substance involved as a product...bromine
HIGHLIGHT Br2(l)
THerefore, the dispalcement of bromine from potassium bromide by chlorine is also a redox reaction.
All single displacement reactions are redox reactions.
In choice C, we have one elemental substance involved as a product... oxygen
Therefore, the decomposition of potassium chlorate to potassium chloride and and oxygen is also a redox reaction.
Any decomposition reaction where at least one of the products is an elemental substance is also a redox reaction.
That leaves choice D as the only possible answer. Choice D is an example of a double replacement reaction.
Double replacement reactions are not redox reactions.
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2. Video ID: © 2008, Project VALUE (Video Assessment Library for Undergraduate Education), Department of Physical Sciences Nicholls State University Author: Glenn V. Lo Narrator: Funded by Louisiana Board of Regents Contract No. LA-DL-SELECT-13-07/08