how do i balence the equation for chemistry?

Question

H3PO3 = H3PO4 + PH3

Answer 1

4 H3PO3 = 3 H3PO4 + PH3 (g)

Answer 2

In general, to balance equations:

1 Balance metals first, if any
2 Balance non-metals, other than hydrogen and oxygen
3 Balance H and O. Do the element that occurs least often first.
5 Repeat above as necessary until the eqn is balanced.

In this case, first balance P:

2H3PO3 ---> H3PO4 + PH3

Notice that O occurs 2x, while H occurrs 3x, so balance O next:
Lowest common multiple of 3 and 4 is 12, so will need 4H3PO3 and 3 H3PO4:

4H3PO3 ---> 3H3PO4 + PH3

Woo hoo! It is now balanced.

Answer 3

4H3PO3=3H3PO4 + PH3