Problem Page Decide whether each chemical reaction in the table below is an oxid

Question

Problem Page

Decide whether each chemical reaction in the table below is an oxidation-reduction ("redox") reaction. If the reaction is a redox reaction, write down the formula of the reducing agent and the formula of the oxidizing agent.

+FeOsCOg+FesCO2g

redox reaction?

yes

no

reducing agent:

oxidizing agent:

+COgH2Og+CO2gH2g

redox reaction?

yes

no

reducing agent:

oxidizing agent:

+CO2g2H2Ol+H3O+aqHCO3aq

redox reaction?

yes

no

reducing agent:

oxidizing agent:

+FeOsCOg+FesCO2g

redox reaction?

yes

no

reducing agent:

oxidizing agent:

+COgH2Og+CO2gH2g

redox reaction?

yes

no

reducing agent:

oxidizing agent:

+CO2g2H2Ol+H3O+aqHCO3aq

redox reaction?

yes

no

reducing agent:

oxidizing agent:

Explanation / Answer

Reaction-1:

FeO + CO = Fe + CO2

Oxidation state of Fe in LHS = +2 and O in lHS = -2

Oxidation state of C in CO = +2 and O = -2

Oxidation state of Fe in RHS = 0

Oxidation state of C in CO2 in RHS = +4 while O = -2

We see that Fe goes from +2 to 0 i.e, it undergoes reduction and C goes from +2 to +4 which means it undergoes oxidation. Hence, this is a redox reaction.

Oxidising agent is one which accepts electrons, or one which gets reduced. So oxidising agent will be FeO. Reducing agent is one which loses electrons or one which undergoes oxidation, hence CO is the reducing agent.

Reaction-2:

CO + H2O = CO2 + H2

oxidation state of C in CO = +2 and O is -2

oxidation state of H in H2O is +1 and O is -2

oxidation state of C in CO2 = +4 and O is -2

oxidation state of H in H2 = 0

We see that C goes from +2 to +4 means it got oxidised. O is same in all compounds with -2. Hydrogen goes from +1 to 0 and hence it got reduced. Hence, this reaction is a redox reaction.

Oxidising agent, as explained in previous example will be the one that gets reduced, so H2O will be oxidising agent. The reducing agent will be one that gets oxidised, and hence CO is the reducing agent.

Reaction-3:

CO2 + H2O = H3O+ + HCO3-

oxidation state of C in CO2 is +4 and O is -2

oxidation state of H in H2O = +1 and O is -2

oxidation state of H3O+ is +1 and that is O is -2 to give overall positive cation.

oxidation state of H in HCO3- is +1, that of C is +4 and that of O is -2 to give overall charge of -1.

We see that C goes from +4 to +4, hence no change here.

O also remains same with -2.

H goes from +1 to +1 only, hence no change here as well. Hence there is no change in oxidation states of individual elements in both reactant and product side. So, this isnt a redox reaction.

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