Question

Balance each of the following redox reactions occurring in acidic aqueous solution. 1) Ni(s)+Cd2+(aq) → Ni2+(aq)+Cd(s) 2) Zn(s)+Na+(aq) → Zn2+(aq)+Na(s) 3) MnO−4(aq)+Al(s) → Mn2+(aq)+Al3+(aq) Express your answer as a chemical equation. Identify all of the phases in your answer.

Answer 1

To balance the given redox reactions, we need to consider the change in oxidation numbers. The oxidation number of each element involved in the reaction is used to balance the equation.

Step-by-step explanation:

Let's balance each of the given redox reactions:

1) Ni(s) + Cd2+(aq) → Ni2+(aq) + Cd(s)

We can see that the oxidation number of Ni goes from 0 to +2, while the oxidation number of Cd goes from +2 to 0.

The balanced equation is:

Ni(s) + Cd2+(aq) → Ni2+(aq) + Cd(s)

2) Zn(s) + Na+(aq) → Zn2+(aq) + Na(s)

Here, the oxidation number of Zn goes from 0 to +2, while the oxidation number of Na goes from +1 to 0.

The balanced equation is:

Zn(s) + 2Na+(aq) → Zn2+(aq) + 2Na(s)

3) MnO−4(aq) + Al(s) → Mn2+(aq) + Al3+(aq)

The oxidation number of Mn goes from +7 to +2, while the oxidation number of Al goes from 0 to +3.

The balanced equation is:

MnO−4(aq) + 8H+(aq) + 5e− + Al(s) → Mn2+(aq) + 4H2O + Al3+(aq)

Answer 2

Ni(s) + Cd₂+(aq) → Ni₂+(aq) + Cd(s)

Balanced Equation: Ni(s) + Cd₂+(aq) → Ni₂+(aq) + Cd(s)

Zn(s) + Na+(aq) → Zn₂+(aq) + Na(s)

Balanced Equation: Zn(s) + 2Na+(aq) → Zn₂+(aq) + 2Na(s)

MnO₄−(aq) + Al(s) → Mn₂+(aq) + Al₃+(aq)

Balanced Equation: 3MnO₄−(aq) + 24H+(aq) + 5Al(s) → 3Mn₂+(aq) + 12H₂O(l) + 5Al₃+(aq)

Step-by-step explanation:

For the first equation, the oxidation states change from 0 to +2 for Ni and +2 to 0 for Cd. To balance it in an acidic solution, you start by assigning oxidation numbers, write half-reactions, balance atoms except for hydrogen and oxygen, balance oxygen with water, balance hydrogen with H+, balance charge with electrons, and finally, balance the number of electrons in both half-reactions to get the balanced equation: Ni(s) + Cd₂+(aq) → Ni₂+(aq) + Cd(s).

The second equation involves Zn and Na+ ions. The oxidation states change from 0 to +2 for Zn and +1 to 0 for Na. To balance it, follow the steps for balancing redox reactions in acidic solutions. Write half-reactions, balance atoms except for hydrogen and oxygen, add water to balance oxygen, add H+ ions to balance hydrogen, balance charges with electrons, and ensure the number of electrons lost equals the number gained to get the balanced equation: Zn(s) + 2Na+(aq) → Zn₂+(aq) + 2Na(s).

Lastly, for the third equation, Mn changes from +7 to +2, while Al changes from 0 to +3. This requires a multi-step process to balance in an acidic solution. Balance each half-reaction for oxidation and reduction, account for oxygen with water molecules and hydrogen with H+ ions. Ensure charges are balanced with electrons and that the total charge and mass are equal on both sides to obtain the balanced equation: 3MnO₄−(aq) + 24H+(aq) + 5Al(s) → 3Mn₂+(aq) + 12H₂O(l) + 5Al₃+(aq).