Oxidation-reduction reactions (often called \"redox\" for short) are reactions t

Question

Oxidation-reduction reactions (often called "redox" for short) are reactions that involve the transfer of electrons from one species to another. Oxidation states, or oxidation numbers, allow chemists to keep track of these electron transfers. In general, one element will lose electrons (oxidation), with the result that it will increase in oxidation number, and another element will gain electrons (reduction), thereby decreasing in oxidation number. An oxidizing agent is an element or compound in a redox reaction that oxidizes another species and itself gets reduced and is therefore the electron acceptor in the reaction. A reducing agent is an element or compound in a redox reaction that reduces another species and itself gets oxidized and is therefore the electron donor in the reaction. As a summary keep in mind the following: Oxidation means an increase in oxidation state and a loss of electrons and involves a reducing agent. Reduction means a decrease in oxidation state and a gain of electrons and involves an oxidizing agent. What element is oxidized in this reaction? Fe_2 O_3 + 3CO rightarrow 2Fe + 3CO_2 Enter the chemical symbol of the element, Which element is reduced in this reaction? Cr_2 O_7^2- + 3 HNO_2 + 5H^+ rightarrow 2Cr^3+ + 3NO_3^- + 4H_2 O Enter the chemical symbol of the element.

Explanation / Answer

A) the given reaction is

Fe203 + 3CO ---> 2Fe + 3C02

write the oxidation numbers

reactants :

Fe ---> +2

O ---> -2

C ----> +2

products :

Fe ----> 0

C ----> +4

O ---> -2

we know that

oxidation is the increase in oxidation number

so

carbon is oxidized

C)

consider the given reaction

Cr2072- + 3HN02 + 5H+ ---> 2Cr+3 + 3N03- + 4H20

write the oxidation numbers

reactants :

Cr ---> +6

H ---> +1

N ---> + 3

O ---> -2

products :

Cr ---> +3

H ---> +1

O ---> -2

N ----> +5

we know that

reduction is decrease in oxidation number

so

Chromium (Cr) is reduced

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