Mission: Electrochemistry

Metal + Non-Metal Redox

100

Question: 2Mg + O₂ → 2MgO. Which element is oxidized?

Write the oxidation half reaction

Magnesium

Mg → Mg²⁺ + 2e^-

200

Question: 2Na + Cl₂ → 2NaCl. 

Which element is reduced?

Oxidizing agent?

Write the oxidation half reaction

Chlorine

Chlorine

Na  → Na + e^-

300

Question: Ca + S → CaS. 

Identify the oxidized and reduced species.

Which is the oxidizing agent

Write the reduction half reaction

Oxidized = Calcium, 

Reduced = Sulfur

Sulfur

S + 2e^- → S^2-

400

Question: 2Al + 3Br₂ → 2AlBr₃. Write the oxidation half-equation.

What are the reducing agent and the oxidizing agent

Al → Al³⁺ + 3e⁻

Reducing agent - Br

Oxidizing agent - Al

500

Question: 2Al + 3Br₂ → 2AlBr₃. 

Identify the oxidized species, reduced species, 

write BOTH half-equations, 

identify the oxidizing agent, reducing agent

Oxidized = Al, Reduced = Br₂, 

Oxidation: Al → Al³⁺ + 3e⁻, 

Reduction: Br₂ + 2e⁻ → 2Br⁻, 

Oxidizing Agent = Br₂, 

Reducing agent -Al

Halogen Displacement

100

Question: Cl₂ + 2KBr → 2KCl + Br₂. 

Which halogen is more reactive? 

Write oxidation half reaction

Chlorine

2BR^- → Br₂ + 2e-

200

Question: Br₂ + 2KI → 2KBr + I₂. 

Which element is oxidized? 

write the reduction half reaction

Iodine (I⁻)

Br₂ + 2e^- → 2Br^-

300

Question: Cl₂ + 2KBr → 2KCl + Br₂. Which species is reduced? Write the oxidation half reaction

Chlorine (Cl₂)

 2Br^- → 2e^- + Br₂

400

Br₂ + 2KI → 2KBr + I₂. Write the oxidation half-equation. Which is the oxidizing agent

2I⁻ → I₂ + 2e⁻

Br

500

1. Cl₂(aq) + 2KBr(aq) → __________________________
2. Br₂(aq) + 2KI(aq) → __________________________
3. Cl₂(aq) + 2KI(aq) → __________________________
4. I₂(aq) + 2KBr(aq) → __________________________
5. Br₂(aq) + 2KCl(aq) → __________________________ 

• Cl₂(aq) + 2KBr(aq) → 2KCl(aq) + Br₂(aq)
• Br₂(aq) + 2KI(aq) → 2KBr(aq) + I₂(aq)
• Cl₂(aq) + 2KI(aq) → 2KCl(aq) + I₂(aq)
• I₂(aq) + 2KBr(aq) → No Reaction
• Br₂(aq) + 2KCl(aq) → No Reaction

Voltaic Cells Basics

100

Question: In a voltaic cell, where does oxidation & reduction occur?

In a Magnesium//Iron galvanic cell, which electrode is oxidised?

Oxidation - Anode ;Reduction - Cathode

Magnesium

200

Question: In a Zn/Cu voltaic cell, 

How does the electrons and conventional current flow?

Electrons from Zn to Cu

Current from Cu to Zn

300

The standard reduction potentials are shown below:

Mg2+(aq)+2e−→Mg(s)E∘=−2.37 

Fe2+(aq)+2e−→Fe(s)E∘=−0.44 

a) Identify the anode and cathode.
b) Calculate the standard cell potential, Ecell∘. 

Show all working.

a)
• Anode: Mg 

• Cathode: Fe

b)

Ecell∘=Ecathode∘−Eanode∘

Ecell∘=(−0.44)−(−2.37)

Ecell∘=+1.93 

400

The standard reduction potentials are shown below:

Al3+(aq)+3e−→Al(s)E∘=−1.66 V

Ag+(aq)+e−→Ag(s)E∘=+0.80 V

a) Identify the electrode that loses electrons

b) Calculate the standard cell potential, Show all working.

c) Write the oxidation half-reaction and the reduction half-reaction.

a- Aluminum

b- +2.46V

C- 

Oxidation

Al(s)→Al³⁺(aq)+3e⁻

Reduction:

3Ag⁺(aq)+3e⁻→3Ag(s)

500

Question: A voltaic cell consists of a magnesium electrode and a copper electrode. 

Identify the anode, cathode, 

direction of electron flow, 

where oxidation occurs, and where reduction occurs.

Anode = Mg, 

Cathode = Cu, 

Electrons flow Mg → Cu, 

Oxidation at anode, 

Reduction at cathode

Cell Potential Calculations

100

Question: A Ni/Ag cell is constructed. Which electrode is the cathode? Which is the oxidizing agent?

Ni²⁺ + 2e⁻ → Ni E° = −0.25 V

Ag⁺ + e⁻ → Ag E° = +0.80 V

Silver

Silver

200

Question: An Al/Fe cell is constructed. 

Which electrode is the anode? 

Which electrode increases in mass after sometime?

Al³⁺ + 3e⁻ → Al E° = −1.66 V

Fe²⁺ + 2e⁻ → Fe E° = −0.44 V

Aluminum

Iron

300

Question: A Na/Cu cell is constructed. Calculate E°cell.

• Na⁺ + e⁻ → Na  E° = −2.71 V
• Cu²⁺ + 2e⁻ → Cu E° = +0.34 V

Is the reaction spontaneous?

What happens to the sodium electrode after sometime? 

3.05 V

400

Question: A Pb/Fe cell is constructed. 

Which electrode is the cathode? 

Calculate the Emf of the cell. Is the cell spontaneous?

What happens to the mass of the lead electrode over time?

• Pb²⁺ + 2e⁻ → Pb E° = −0.13 V
• Fe²⁺ + 2e⁻ → Fe E° = −0.44 V

Lead

-0.31

Not spontaneous

500

Question: A voltaic cell is constructed using Mg/Mg²⁺ and Cu/Cu²⁺ half-cells. 

Given 

E°(Mg²⁺/Mg) = -2.37 V 

E°(Cu²⁺/Cu) = +0.34 V. 

Identify the anode, cathode, 

calculate E°cell. 

What happens to the mass of the magnesium electrode over time?

Anode = Mg, Cathode = Cu, 

E°cell = 0.34 − (−2.37) = 2.71 V

Mass decreases, metal changes to ions

Mixed Challenge

100

Question: What does OIL RIG stand for?

Write down a metal - non metal redox reaction with the respective half reactions

Oxidation Is Loss, Reduction Is Gain

Varies

200

Question: Zn + Cu²⁺ → Zn²⁺ + Cu. 

Which species is oxidized?

Which is the reducing agent

Write the oxidation half reaction

Zinc

Zinc

Zn → Zn²⁺ + 2e^-

300

Question: A Mg/Cu voltaic cell is built. 

Which electrode is the anode?

How does current flow?

Magnesium

From Copper to Magnesium

400

Question: Cl₂ + 2Br⁻ → 2Cl⁻ + Br₂. 

Which species loses electrons?

Which species is oxidized

Which is the reducing Agent

Br⁻

Br

Br

500

Question: Br₂ + 2I⁻ → 2Br⁻ + I₂. 

Identify the oxidized species, reduced species, oxidizing agent, reducing agent, 

write BOTH half-equations, and determine the total number of electrons transferred.

Oxidized = I⁻, Reduced = Br₂, Oxidizing Agent = Br₂, Reducing Agent = I⁻, 

Oxidation: 2I⁻ → I₂ + 2e⁻, 

Reduction: Br₂ + 2e⁻ → 2Br⁻, 

Total electrons transferred = 2