Redox Reactions — MHT-CET Chemistry

Formulas (3)

• Finding One Atom's Oxidation Number · Sum rule
  $$\sum (\text{oxidation numbers}) = \text{charge on the species}$$
• When the Formula Is Not Enough: Peroxides, Chains and Averages · Peroxide acid
  $$\mathrm{H_2SO_5}:\ 2(+1) + x + 2(-1) + 3(-2) = 0 \Rightarrow x = +6$$
• The Change in Oxidation Number Across a Reaction · Change in oxidation number
  $$\Delta = \text{ON}_{\text{product}} - \text{ON}_{\text{reactant}}\quad(\Delta > 0:\ \text{oxidation})$$

Watch out for (4)

• Treating an ion as neutral
  → Finding One Atom's Oxidation Number
• Giving oxygen −2 next to fluorine
  → Finding One Atom's Oxidation Number
• Reading +8 for sulphur
  → When the Formula Is Not Enough: Peroxides, Chains and Averages
• Calling chromate ⇌ dichromate a redox reaction
  → The Change in Oxidation Number Across a Reaction

Formulas (1)

• Electrons Transferred and the Balancing Coefficients · Electron balance
  $$n_{\text{lost}} \times (\text{coefficient}) = n_{\text{gained}} \times (\text{coefficient})$$

Watch out for (3)

• Picking hydrogen or oxygen because they appear on both sides
  → Which Element Is Oxidised, Which Is Reduced — and Is It Redox at All?
• Counting electrons per ion instead of per atom
  → Electrons Transferred and the Balancing Coefficients
• Forgetting that N₂ has two atoms
  → Electrons Transferred and the Balancing Coefficients

Formulas (1)

• Oxidising and Reducing Agents and Their Strength · Can A reduce B?
  $$\text{A reduces B if } E^\circ_{\text{B}} > E^\circ_{\text{A}^{n+}/\text{A}}$$

Reference tables (1)

Watch out for (1)

• Confusing the strongest oxidising agent with the weakest reducing agent
  → Oxidising and Reducing Agents and Their Strength