The equation in which the number of atoms of all the molecules is equal on both sides of the equation is known as a balanced chemical equation.
Example;
Just a random chemical compound right now.
You could take salt, for example. The chemical formula is NaCl. That would be considered balanced, because the amount of sodium and the amount of chlorine is the same.
I hope this helps. I’ve never learned this and just took a definition from google lol.
Zinc
Cadmium
Copper
Chromium
Mercury
Lead
These are the heavy metal contaminants if it' something you were looking for
After dipping the litmus paper strips in the solutions, the answer to the question is that one is acidic because according to brad's observation on turned red and the others are basic or alkaline with the two papers turning blue.