How would you balance this redox reaction by oxidation number method?
C + O2 = CO2
C + O2 = CO2
C changes from zero on the left to 4+ on the right. A loss of 4e.
2 O changes from zero on the left to 4- on the right. A gain of 4e.
Yea! Loss of e = gain of e means it is balanced.
To balance the redox reaction using the oxidation number method, follow these steps:
Step 1: Assign oxidation numbers to all elements.
C + O2 = CO2
Since oxygen (O) is usually assigned an oxidation number of -2, and carbon (C) is more electronegative, we can assume that the oxidation number of carbon is +4 in CO2.
Step 2: Identify which elements are being oxidized and reduced.
In this reaction, carbon (C) is being oxidized from an oxidation state of 0 to +4, and oxygen (O) is being reduced from an oxidation state of 0 to -2.
Step 3: Balance the atoms and charges for each half-reaction separately.
Oxidation half-reaction: C --> CO2
Since carbon is being oxidized, it loses 4 electrons:
C --> CO2 + 4e-
Reduction half-reaction: O2 --> O2-
Since oxygen is being reduced, it gains 2 electrons for each O atom:
O2 + 4e- --> 2O2-
Step 4: Multiply the half-reactions by appropriate coefficients to balance the number of electrons transferred.
Multiply the oxidation reaction by 2 to balance the electrons:
2C --> 2CO2 + 8e-
Multiply the reduction reaction by 4 to balance the electrons:
4O2 + 16e- --> 8O2-
Step 5: Finally, add the two half-reactions and cancel out any common species on both sides of the equation.
Adding the two half-reactions, we get:
2C + 4O2 --> 2CO2 + 8O2-
Cancelling out the common species on both sides, we arrive at the balanced equation:
2C + 2O2 --> 2CO2
To balance the given redox reaction using the oxidation number method, follow these steps:
Step 1: Assign oxidation numbers to each element in the reaction.
C + O2 → CO2
The oxidation number of carbon (C) is not known, so let's assume it is x.
Oxygen (O) always has an oxidation number of -2 in compounds, so the oxidation number is -2 for each O atom.
The compound CO2 is neutral, so the sum of the oxidation numbers must be zero.
C + O2 → CO2
x + 2(-2) = 0
Simplifying the equation:
x - 4 = 0
x = +4
The oxidation number of carbon (C) is +4.
Step 2: Determine the changes in oxidation numbers for each element.
C + O2 → CO2
The oxidation number of carbon changes from unknown (x) to +4.
The oxidation number of oxygen changes from -2 to 0.
Step 3: Balance the oxidation-reduction half-reactions.
Since carbon is oxidized from an oxidation state of x to +4, it is undergoing oxidation.
Since oxygen is reduced from an oxidation state of -2 to 0, it is undergoing reduction.
Oxidation half-reaction: C → +4
Reduction half-reaction: O2 → 2O^0
Step 4: Balance the number of atoms in the half-reactions.
Since the carbon atom is already balanced, we only need to balance the number of oxygen atoms.
In the reduction half-reaction, there are 2 oxygen atoms on the left side, but only 2 oxygen atoms on the right side. To balance it, we need to add a coefficient of 2 in front of O2.
Oxidation half-reaction: C → +4
Reduction half-reaction: 2O2 → 4O^0
Step 5: Balance the charges in the half-reactions.
Since there is no charge on the carbon atom in the oxidation half-reaction and no charge change in the reduction half-reaction, the charges are already balanced.
Oxidation half-reaction: C → +4
Reduction half-reaction: 2O2 → 4O^0
Step 6: Balance the electrons in the half-reactions.
In the oxidation half-reaction, the carbon atom loses 4 electrons.
In the reduction half-reaction, the 4 oxygen atoms gain 4 electrons from the oxygen molecule.
Oxidation half-reaction: C - 4e⁻ → +4
Reduction half-reaction: 2O2 + 4e⁻ → 4O^0
Step 7: Balance the reactant and product species in the combined reaction.
To balance the electrons in the two half-reactions, we must first multiply the oxidation half-reaction by 2 and the reduction half-reaction by 1.
Then, we can combine the two half-reactions, making sure that the number of electrons cancels out.
2(C - 4e⁻ → +4)
2(2O2 + 4e⁻ → 4O^0)
Resulting balanced redox reaction:
2C + O2 → 2CO2
The balanced redox reaction is:
2C + O2 → 2CO2