Question

Balance the following equation:



HCl + Mg(OH)2 -> MgCl2 + H2O

Answer 1

To balance the chemical equation HCl + Mg(OH)₂ -> MgCl₂ + H₂O, follow these steps:

1. **Count the number of each type of atom on both sides of the equation.**

- Reactants:
- H: 1 (from HCl) + 2 (from Mg(OH)₂) = 3 H
- Cl: 1 (from HCl)
- Mg: 1 (from Mg(OH)₂)
- O: 2 (from Mg(OH)₂)

- Products:
- H: 2 (from H₂O)
- Cl: 2 (from MgCl₂)
- Mg: 1 (from MgCl₂)
- O: 1 (from H₂O)

2. **Balance the Cl and H atoms first.**

- Since we have 2 Cl in the products, we need to have 2 HCl in the reactants to provide the 2 Cl.

Revised equation:
\( 2 \, \text{HCl} + \text{Mg(OH)}_2 \rightarrow \text{MgCl}_2 + \text{H}_2\text{O} \)

3. **Count again:**

- Reactants:
- H: 2 (from 2 HCl) + 2 (from Mg(OH)₂) = 4 H
- Cl: 2 (from 2 HCl)
- Mg: 1 (from Mg(OH)₂)
- O: 2 (from Mg(OH)₂)

- Products:
- H: 2 (from H₂O) → We need another water molecule to balance the H.
- Cl: 2 (from MgCl₂)
- Mg: 1 (from MgCl₂)
- O: 1 (from H₂O)

4. **Adjust the number of water molecules:**

Adjust the water to balance the hydrogen:

Revised equation:
\( 2 \, \text{HCl} + \text{Mg(OH)}_2 \rightarrow \text{MgCl}_2 + 2 \, \text{H}_2\text{O} \)

5. **Final count:**

- Reactants:
- H: 2 (from 2 HCl) + 2 (from Mg(OH)₂) = 4 H
- Cl: 2 (from 2 HCl)
- Mg: 1 (from Mg(OH)₂)
- O: 2 (from Mg(OH)₂)

- Products:
- H: 2 (from H₂O) + 2 (from the second H₂O) = 4 H
- Cl: 2 (from MgCl₂)
- Mg: 1 (from MgCl₂)
- O: 1 (from 1st H₂O) + 1 (from 2nd H₂O) = 2 O

This equation is now balanced:

\[
\boxed{2 \, \text{HCl} + \text{Mg(OH)}_2 \rightarrow \text{MgCl}_2 + 2 \, \text{H}_2\text{O}}
\]