Answer:
The coefficients in order are 2, 1, 1
Explanation:
Each side of the reaction needs to have the same number of each element due to conservation of matter.
First I looked at what was uneven, notice there are 2 Na on the left side and 4 Na on the left. The easiest way to fix that is to add a 2 on the Na2HPO4:
2(Na2HPO4)--> Na4P2O7 + H2O
Next take count of each element on both sides to see if the 2 balanced everything:
On the left there are 4 Na, 2 H, 2 P, and 8 O
On the right there are 4 Na, 2 H, 2 P, and 8 O
Since both sides match, you are done!
