LT#2: Writing Balanced Eqns for Redox

Question 1

What are the steps for balancing a half reaction in neutral conditions?

Answer 1

1. Write the correct formulas for the reactants and products.
2. Balance the atoms using coefficients
3. Add electrons to balance the total charge left side vs right.

Question 2

What are the steps for balancing a half reaction in acidic conditions?

Answer 2

1. Write the correct formulas for the reactants and products.
2. Balance any atoms other than oxygen and hydrogen first.
3. Balance any oxygen atoms by adding water molecules.
4. Balance any hydrogen atoms by adding hydrogen ions.
5. Balance the charges by adding electrons.

Question 3

What are the steps for balancing a half reaction in basic conditions?

Answer 3

1. Write the correct formulas for the reactants and products.
2. Balance any atoms other than oxygen and hydrogen first.
3. Balance any oxygen and hydrogen atoms as if the conditions are acidic
4. Add enough OH1- to both sides of the equation to react with any H1+ present to make water.
5. Simplify the reaction by removing any water present on both sides of the equation.
6. Balance the charges by adding electrons.

Question 4

What concept does the Half Reaction Method use to balance redox equations?

Answer 4

That the number of electrons lost in the oxidation must be the same number of electrons gained in the reduction

Question 5

What are the steps involved in the half reaction method of balancing redox reactions?

Answer 5

1. Write the unbalanced net ionic equation if not given to you.
2. Split this equation into 2 half reactions.
3. Balance each half reaction separately using appropriate conditions.
4. Determine the Lowest Common Multiple (LCM) for the electrons, and multiple both half reactions by a coefficient to make the number of electrons the LCM.
5. Algebraically add the 2 half reactions together.
6. Add spectator ions if required.

Question 6

What concept does the Oxidation Number Method use to balance redox equations?

Answer 6

That the total increase in the oxidation number of the oxidized element equals the total decrease in the oxidation number of the reduced element.

Question 7

What are the steps involved in the oxidation number method of balancing redox reactions?

Answer 7

1. Write the unbalanced net ionic equation if not given to you.
2. Assign oxidation numbers to all the elements.
3. Find the numerical values of the increase and the decrease in the oxidation numbers.
4. Determine the smallest whole number ratio for the oxidized and reduced elements so that the oxidation number increase and decrease are equal. Use this ratio to balance the number of atoms of the oxidized/reduced elements.
5. Balance the other elements by inspection if possible.
6. For reactions in acidic or basic conditions, include water, hydrogen ions or hydroxide ions as needed.