Answer: 2Cr + 3Br2 Yields 3CrBr3
Explanation:
We know that 4a is not balanced because there are 3 Nitrogen atoms on the reactants side and 2 on the products side.
We know that 4c is not balanced because there are 4 Chlorine atoms on the reactants side and 2 on the products side. (Remember there are 2 Cl2 atoms. Therefore, 2 times 2 means there are 4 Chlorine atoms on the reactants side)
Finally, we know the answer is not 4d because there is 1 Potassium on the reactants side and 2 potassiums on the products side.
Therefore, the answer must be 4b, which contains 2 Chromium atoms and 6 bromine atoms on each side
