To balance the chemical equation HCl + Mg(OH)₂ -> MgCl₂ + H₂O, follow these steps:
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Count the number of each type of atom on both sides of the equation.
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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)
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Products:
- H: 2 (from H₂O)
- Cl: 2 (from MgCl₂)
- Mg: 1 (from MgCl₂)
- O: 1 (from H₂O)
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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:
\( 2 , \text{HCl} + \text{Mg(OH)}_2 \rightarrow \text{MgCl}_2 + \text{H}_2\text{O} \) -
Count again:
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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)
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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)
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Adjust the number of water molecules:
Adjust the water to balance the hydrogen:
Revised equation:
\( 2 , \text{HCl} + \text{Mg(OH)}_2 \rightarrow \text{MgCl}_2 + 2 , \text{H}_2\text{O} \) -
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)
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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
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This equation is now balanced:
\[ \boxed{2 , \text{HCl} + \text{Mg(OH)}_2 \rightarrow \text{MgCl}_2 + 2 , \text{H}_2\text{O}} \]