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Balancing Eąuations

Balance the following equation:

Mg₃(P0₄)₂(.r) + NaCl(fl^)

Na₃P0₄Ca«) + MgCl₂(^) -

SoSution

In the equation, the correct formulas are written.

Na₃P0₄(a<j) + MgCl₂(aę) --- Mg₃(P0₄)2(s) + NaCl(a<?)

1SJ111S When we compare the number of ions on the reactant and product sides, we find that the eąuation is not balanced. In this eąuation, it is morę convenient to balance the phosphate polyatomic ion as a group instead of its individual atoms.

Reactants	Products
Na3P04(a<?) + MgCl2(a<?) —	- Mg3(P04)2(*) + NaCl(^)
3Na^+	1 Na^+ Not balanced
1 P04^3~	2 P04^3 Not balanced
lMg^2+	3 Mg^2+ Not balanced
2cr	1 Cl Not balanced

dfeiljidfcll We begin with the formula of Mg₃(P0₄)₂, which is the most com-plex. A 3 in front of MgCl₂ balances magnesium and a 2 in front of Na₃P0₄ balances the phosphate ion. Looking again at each of j    the ions in the reactants and products, we see that the sodium and

chloride ions are not yet equal. A 6 in front of the NaCl balances the equation.

STEP 4

A check of the atoms indicates the equation is balanced.

'    2Na₃P0₄(a^) + 3MgCl ₂{aq) -- Mg₃(P0₄)₂(s) + 6NaCl(a₉)

Reactants    Products

2Na₃P0₄(ci<?) + 3MgCl₂(fl<?)-- Mg₃(P0₄)₂(.s) + 6NaCl(at?)

Balanced

6 Na⁺    — 6 Na⁺

2 P0₄^?_    = 2 P0₄^3-

—    A/T- 2 +

—    J Mg

ócr

—    6cr