How do I balance this chemical equation?

Question

Ca(OH)2 + H3 PO4 = > H2 O + Ca4 (PO)2

oops, typo, I meant:
Ca(OH)2 + H3 PO4 = > H2 O + Ca4 (PO4)2

Answer 1

Ca(OH)2 + H3 PO4 = > H2 O + Ca4 (PO)2

Write a system of mass balance equations for each element with the coefficients of each compound as an unknown. Solve the system of equations. This works for any chemical equation that you must balance.

A Ca(OH)2 + B H3 PO4 = > C H2 O + D Ca4 (PO)2

Calcium:
A=4D

Phosphorus
B=2D

Oxygen
2A+4B=C+2D

Hydrogen
2A+3B=2C

Solve the system of four equations

A=4D
B=2D
2A+4B=C+2D
2A+3B=2C
---------------

Substituting for A and B in the oxygen equation

8D+8D=C+2D
C=14D

You may stop at this point as have defined A,B, and C in terms of D.


A=4D
B=2D
C=14D


Thus you can write
4 Ca(OH)2 + 2 H3 PO4 = > 14 H2 O + Ca4 (PO)2

Note, this algebraic method is broadly applicable. I hope you adopt it as it can tackle the most difficult problems.

Answer 2

I would probably start with calcium (Ca)

The products include 4 Ca atoms so we need to put a 4 in front of the Ca(OH)2 in order to make the Ca's balanced.

Next maybe look at phosphorus (P).
The reactants 2 phosophorus atoms so we need a 2 in front of H3 PO4 to balance the P's.

Lets see where we are so far:
4 Ca(OH)2 + 2 H3 PO4 => H2 O + Ca4(PO)2

Checking oxygen (O)
We have 4*2 + 2*4 = 16 oxygen atoms in the products, and,
only 3 O's in the reactants. A 14 in front of the H2O will put the O's in balance (14+2=16 in reactants).

4 Ca(OH)2 + 2 H3 PO4 => 14 H2O + ca4(PO)2

okay, if we are lucky and good, the H's will be in balance

reactants H's: 4*2 + 2*3 = 14
products H's: 14

bueno
we got it

you gotta love chemistry

Answer 3

You've got the equation written wrong, which is going to make it very difficult to balance. You have the wrong products. The equation should appear as follows:

3Ca(OH)2 + 2H3PO4 => 6H20 + Ca3(PO4)2