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# How can I balance this chemical equation? Sodium phosphate and calcium chloride react to form calcium phosphate and sodium chloride

Jul 23, 2014

This is a double replacement reaction. Here's how to balance double replacement equations

#### Explanation:

$\text{Na"_3"PO"_4 + "CaCl"_2 → "Ca"_3("PO"_4)_2 + "NaCl}$

1. Start with the most complicated formula, "Ca"_3("PO"_4)_2.

Put a 1 in front of it. We have now fixed the number of $\text{Ca}$ atoms and ${\text{PO}}_{4}$ groups.

$\text{Na"_3"PO"_4 + "CaCl"_2 →color(red)(1)"Ca"_3("PO"_4)_2 + "NaCl}$

2. Balance $\text{Ca}$. Put a 3 in front of ${\text{CaCl}}_{2}$.

$\text{Na"_3"PO"_4 + color(blue)(3)"CaCl"_2 → color(red)(1)"Ca"_3("PO"_4)_2 + "NaCl}$

.

3. Balance ${\text{PO}}_{4}$. Put a 2 in front of ${\text{Na"_3"PO}}_{4}$.

$\textcolor{\mathmr{and} a n \ge}{2} \text{Na"_3"PO"_4 + color(blue)(3)"CaCl"_2 → color(red)(1) "Ca"_3("PO"_4)_2 + "NaCl}$

4. Balance $\text{Na}$. Put a 6 in front of $\text{NaCl}$.

$\textcolor{\mathmr{and} a n \ge}{2} \text{Na"_3"PO"_4 + color(blue)(3) "CaCl"_2 → color(red)(1)"Ca"_3("PO"_4)_2 + color(teal)(6) "NaCl}$

5. Every formula has a coefficient.

The equation should be balanced. Let's check.

Left hand side: $\text{6 Na; 2 PO"_4"; 3 Ca; 6 Cl}$
Right hand side: $\text{3 Ca; 2 PO"_4"; 6 Na; 6 Cl}$.

Everything checks. the balanced equation is

$\text{2Na"_3"PO"_4 + "3CaCl"_2 → "Ca"_3("PO"_4)_2 + "6NaCl}$