How does a balanced chemical equation illustrate that mass is never lost or gained in a chemical reaction?

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.

c is the answer because when something is left after something evaporates that shows the chemical change.

that's what i got you can count the number of atoms