Question

Закінчіть рівняння хімічних реакцій, методом електронного балансу розставте коефіцієнти, укажіть процеси окиснення та відновлення, окисники та відновники: Cu + HNO3(конц.) → Cu + HNO3(розб.) → Cu + H2SO4(конц.) →

Answer 1

Ответ:

1) Cu + HNO3(конц.) → Cu(NO3)2 + NO + H2O

Процес окиснення: Cu → Cu^2+

Процес відновлення: HNO3 → NO

Окисник: HNO3

Відновник: Cu

2) Cu + 2HNO3(розб.) → Cu(NO3)2 + NO + H2O

Процес окиснення: Cu → Cu^2+

Процес відновлення: HNO3 → NO

Окисник: HNO3

Відновник: Cu

3) Cu + 2H2SO4 (конц.) → CuSO4 + SO2↑ + 2H2O

Процес окиснення: Cu → Cu^2+

Процес відновлення: ні

Окисник: H2SO4

Відновник: Cu

Answer 2

Balancing the Chemical Equation using the Electron Balance Method

To balance the chemical equation using the electron balance method, we need to ensure that the number of electrons gained in the reduction half-reaction is equal to the number of electrons lost in the oxidation half-reaction. Let's balance the given equation step by step:

Step 1: Identify the oxidation and reduction half-reactions

In the given equation, we have Cu reacting with HNO3 and H2SO4. Let's identify the oxidation and reduction half-reactions:

Oxidation Half-Reaction: Cu → Cu^3+ Reduction Half-Reaction: HNO3 → NO + H2O

Step 2: Balance the atoms other than hydrogen and oxygen

In the oxidation half-reaction, we have one Cu atom on both sides, so it is already balanced.

In the reduction half-reaction, we have one N atom on the left side and one N atom on the right side. Therefore, the number of N atoms is already balanced.

Step 3: Balance the oxygen atoms

In the oxidation half-reaction, we have no oxygen atoms on either side.

In the reduction half-reaction, we have three oxygen atoms on the left side and one oxygen atom on the right side. To balance the oxygen atoms, we need to add two water molecules (H2O) to the right side of the equation:

HNO3 → NO + 2H2O

Step 4: Balance the hydrogen atoms

In the oxidation half-reaction, we have no hydrogen atoms on either side.

In the reduction half-reaction, we have three hydrogen atoms on the left side and four hydrogen atoms on the right side. To balance the hydrogen atoms, we need to add one hydrogen ion (H+) to the left side of the equation:

HNO3 + H+ → NO + 2H2O

Step 5: Balance the charges

In the oxidation half-reaction, we have a charge of 0 on both sides.

In the reduction half-reaction, we have a charge of +1 on the left side and a charge of 0 on the right side. To balance the charges, we need to add one electron (e-) to the left side of the equation:

HNO3 + H+ + e- → NO + 2H2O

Step 6: Balance the electrons

Now, we need to balance the number of electrons gained in the reduction half-reaction with the number of electrons lost in the oxidation half-reaction. In this case, the number of electrons gained is 1, and the number of electrons lost is also 1. Therefore, the electrons are already balanced.

Step 7: Combine the half-reactions

Finally, we can combine the oxidation and reduction half-reactions to obtain the balanced chemical equation:

Cu + 4HNO3 + H+ + e- → Cu^3+ + NO + 2H2O

Oxidation and Reduction Processes, Oxidizing and Reducing Agents

In the balanced chemical equation, the oxidation process occurs at the Cu atom, which loses electrons and is oxidized from Cu to Cu^3+. The reduction process occurs at the HNO3 molecule, which gains electrons and is reduced from HNO3 to NO.

Therefore, Cu is the reducing agent because it causes the reduction of HNO3 to NO by losing electrons, and HNO3 is the oxidizing agent because it causes the oxidation of Cu to Cu^3+ by accepting electrons.

Summary

The balanced chemical equation using the electron balance method is:

Cu + 4HNO3 + H+ + e- → Cu^3+ + NO + 2H2O

In this equation, Cu is oxidized to Cu^3+ (oxidation process), and HNO3 is reduced to NO (reduction process). Cu is the reducing agent, and HNO3 is the oxidizing agent.