Question

The reaction of zinc (II) hydroxide with phosphoric acid produces zinc (II) phosphate and water.

___ Zn(OH)2+____ H2PO4 Arrow right ___ Zn3(PO4)2 + H2O

Balance the reaction by completing the chemical equation with the molar coefficients.

Answer 1

To balance the reaction of zinc (II) hydroxide (Zn(OH)₂) with phosphoric acid (H₃PO₄) to produce zinc (II) phosphate (Zn₃(PO₄)₂) and water (H₂O), we begin by writing the unbalanced equation:

\[
\text{Zn(OH)}_2 + \text{H}_3\text{PO}_4 \rightarrow \text{Zn}_3(\text{PO}_4)_2 + \text{H}_2\text{O}
\]

To balance this reaction, we can follow these steps:

1. **Count the number of each atom in the reactants and products.**
2. **Adjust coefficients to balance the atoms one type at a time.**

### Step 1: Write the unbalanced equation
\[
\text{___ Zn(OH)}_2 + \text{____ H}_3\text{PO}_4 \rightarrow \text{___ Zn}_3(\text{PO}_4)_2 + \text{_____ H}_2\text{O}
\]

### Step 2: Balance Zinc (Zn)
From the product Zn₃(PO₄)₂, we see that we need 3 zinc atoms:

- Therefore, we need 3 Zn(OH)₂:

\[
\text{3 Zn(OH)}_2
\]

### Step 3: Balance Phosphate (PO₄)
From the product Zn₃(PO₄)₂, we see we need 2 phosphate groups (PO₄). Since each H₃PO₄ contains one phosphate, we need 2 H₃PO₄:

- Therefore, we have:

\[
\text{2 H}_3\text{PO}_4
\]

### Step 4: Balance Water (H₂O)
To find the water produced, we can use the total number of hydrogens:

From the reactants:
- Each Zn(OH)₂ has 2 hydrogens and we have 3, contributing 6 H.
- Each H₃PO₄ has 3 hydrogens and we need 2, contributing 6 H.
So total H in reactants = 6 + 6 = 12 H

From the products:
- Each H₂O has 2 hydrogens. To balance 12 H, we need:

\[
\text{6 H}_2\text{O}
\]

### Step 5: Combine everything into the balanced equation

Putting it all together, we have the balanced equation:

\[
\text{3 Zn(OH)}_2 + \text{2 H}_3\text{PO}_4 \rightarrow \text{1 Zn}_3(\text{PO}_4)_2 + \text{6 H}_2\text{O}
\]

### Final Balanced Equation:

\[
3 \text{ Zn(OH)}_2 + 2 \text{ H}_3\text{PO}_4 \rightarrow 1 \text{ Zn}_3(\text{PO}_4)_2 + 6 \text{ H}_2\text{O}
\]

So the coefficients are:
- **3, 2, 1, 6** for Zn(OH)₂, H₃PO₄, Zn₃(PO₄)₂, and H₂O, respectively.