Question

K2Cr2O7+...+H2O=Cr(OH)3+Na2SO4+... Составьте уравнение реакции, используя метод электронного баланса.

Answer 1

Решение:
3Na₂SO₃ + K₂Cr₂O₇ + 4H₂O = 2Cr(OH)₃↓ + 2KOH + 3Na₂SO₄
S⁺⁴ -2e⁻---> S⁺⁶     |3 (S⁺⁴ - восстановитель)
Cr⁺⁶ +3e⁻---> Cr⁺³ |2 (Cr⁺⁶ - окислитель)

Answer 2

Balancing the Chemical Equation Using the Electron Balance Method

The given chemical equation is:

K2Cr2O7 + H2O = Cr(OH)3 + Na2SO4

To balance this equation using the electron balance method, we need to ensure that the number of electrons lost in the oxidation half-reaction is equal to the number of electrons gained in the reduction half-reaction.

1. Identify the Oxidation and Reduction Half-Reactions: - The oxidation half-reaction involves the loss of electrons, while the reduction half-reaction involves the gain of electrons. - In this case, the chromium in K2Cr2O7 undergoes reduction, and the hydrogen in H2O undergoes oxidation.

2. Balance the Atoms: - First, balance the atoms in each half-reaction, excluding oxygen and hydrogen.

Oxidation Half-Reaction: Cr2O7^2- → Cr^3+ Reduction Half-Reaction: H2O → OH^-

3. Balance Oxygen Atoms: - Add water molecules (H2O) to one side of the equation to balance the oxygen atoms.

Oxidation Half-Reaction: Cr2O7^2- → Cr^3+ + 7H2O

Reduction Half-Reaction: H2O → 2OH^- + 2H2O

4. Balance Hydrogen Atoms: - Add hydrogen ions (H^+) to the other side of the equation to balance the hydrogen atoms.

Oxidation Half-Reaction: Cr2O7^2- + 14H^+ → Cr^3+ + 7H2O

Reduction Half-Reaction: H2O + 2e^- → 2OH^- + 2H2O

5. Balance Charge: - Balance the charges in each half-reaction by adding electrons.

Oxidation Half-Reaction: Cr2O7^2- + 14H^+ + 6e^- → Cr^3+ + 7H2O

Reduction Half-Reaction: 2H2O + 2e^- → 2OH^- + 2H2O

6. Combine the Half-Reactions: - Multiply the half-reactions by appropriate coefficients to ensure that the number of electrons lost equals the number gained.

Overall Balanced Equation: 14H^+ + Cr2O7^2- + 6H2O + 6e^- → Cr^3+ + 7H2O + 6e^- + 14H^+ (after canceling out the electrons)

Simplified Balanced Equation: K2Cr2O7 + 4H2O → 2Cr(OH)3 + 2K^+ + 2Cr^3+ + 3O2

This balanced equation satisfies the electron balance method for the given chemical reaction.