Ok one more!
Write the balanced equations and assign oxidation numbers to all atoms in these two reactions involving iron. If the effective oxidation number of any particular atom changes during the reaction then a redox reaction has occurred. If a redox reaction takes place then write the half reactions involved.
A. Solid iron (II) oxide is exposed to carbon monoxide and high heat. The process produces molten iron in the liquid state and carbon dioxide.
B. Solid FeCO3 is heated strongly to form FeO and carbon dioxide.
Do you know how to assign oxidation numbers? If not, here is a good site. Both reactions you have are redox reactions.
http://www.chemteam.info/Redox/Redox-Rules.html
To answer these questions, we need to determine the oxidation numbers of the atoms in each chemical species involved in the reactions.
A. The reaction is:
FeO(s) + CO(g) → Fe(l) + CO2(g)
1. Iron (II) oxide (FeO):
To determine the oxidation numbers in FeO, we assign x to the oxidation number of Fe and -2 to O. Since O typically has an oxidation number of -2 in compounds, the total oxidation number of FeO is 0. Hence, (x) + 2(-2) = 0, and solving for x gives +2 as the oxidation number of Fe.
2. Carbon monoxide (CO):
The oxidation number of O is typically -2, so we assign x to C and -2 to O. Hence, (x) + (-2) = 0, and solving for x gives +2 as the oxidation number of C.
3. Molten iron (Fe):
Since FeO was reduced to Fe, the oxidation number of Fe in Fe(l) is 0.
4. Carbon dioxide (CO2):
The oxidation number of O is typically -2. Thus, assigning x to C, we have (x) + 2(-2) = 0. Solving for x gives +4 as the oxidation number of C.
From this analysis, we can see that the oxidation state of Fe changes from +2 in FeO to 0 in Fe(l), while the oxidation state of C changes from +2 in CO to +4 in CO2. Hence, the reaction is a redox reaction.
To write the half-reactions, we can consider the species undergoing oxidation and reduction separately:
Oxidation half-reaction:
FeO(s) → Fe(l) + 2e^-
Reduction half-reaction:
CO(g) + 2e^- → CO2(g)
B. The reaction is:
FeCO3(s) → FeO(s) + CO2(g)
1. Iron (II) carbonate (FeCO3):
To determine the oxidation numbers in FeCO3, we assign x to Fe, -2 to O, and y to C. Hence, (x) + y + 3(-2) = 0. Since CO3 has a charge of -2, the total charge of FeCO3 is 0, so (x) + y - 6 = 0. Hence, if we solve for x and y, we find that the oxidation number of Fe is +2, and the oxidation number of C is +4.
2. Iron (II) oxide (FeO):
Since FeCO3 was oxidized to FeO, the oxidation number of Fe in FeO is +2.
3. Carbon dioxide (CO2):
To determine the oxidation numbers in CO2, we assign x to C and 2(-2) to O. Hence, (x) + 2(-2) = 0, giving us x = +4 as the oxidation number of C.
From this analysis, we can see that the oxidation state of Fe changes from +2 in FeCO3 to +2 in FeO, while the oxidation state of C changes from +4 in FeCO3 to +4 in CO2. Therefore, no redox reaction occurs in this case.
Hence, the half-reactions are not needed for this specific reaction.
Remember, when determining the oxidation numbers, it is crucial to recognize the common patterns and charges associated with elements and polyatomic ions.