1. Which of the following chemical reactions is a redox reaction?
QUESTION:
Which of the following chemical reactions is a redox reaction?
NH3(g) + HCl (g)  NH4Cl(s)
CaCO3(s)  CaO(s) + CO2(g)
2 CaO(s)  2 Ca(s) + O2(g)
D. Ag+(aq) + Cl-(aq)  AgCl(s)
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 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, one of the reactions can be easily identified as a redox reaction.
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. Only choice C involves elemental substances... calcium
HIGHLIGHT Ca(s)
... and oxygen
HIGHLIGHT O2(g)
Therefore, the reaction in choice C is a redox reaction.
By assigning oxidation numbers, we can verify that the reactions in choices A, B, and D are not redox reactions.
But we dont’ have to in this case, since there is only one correct answer.
In case you’re wondering about choice D. Silver ion
HIGHLIGHT Ag+
and chloride ion
HIGHLIGHT Cl-
do not represent elemental substances. The fact that these are ions means that they are part of a compound.
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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