Answer:
Step-by-step explanation:
Because if the equation is truly balanced, the elements on one side equal the element numbers on the other. Take a simple example.
Ba(OH)2 + 2HCl ==> BaCl2 + 2HOH
Now consider what is true.
Element Number of the left Number on the right.
Ba 1 1
O 2 2
H 4 4
Cl 2 2
Nothing has changed going from the left to the right. You may wonder how you get 4 for the hydrogens.
Ba(OH)2 has 2 hydrogens. You multiply the 2 by the hydrogens in the brackets.
2HCl = The 2 in front affects both the hydrogens and the chlorines. There are 2 hydrogens from the HCl
Total: 2 + 2 = 4 hydrogens. The right side is done the same way.
You are not getting different results on the right side than those that you had on the left. Mass is preserved. 1 Ba + 2 Os + 4Hs and 2 Cls on the left, gives the same numbers on the right. There is no loss of mass.