CHEMISTRY COMMUNITY

Question h.1 asks why you can't just add an extra O molecule to balance the equation? Why wouldn't we be able to do that?

Hi!
I think because singular oxygen atoms are not a proper "product" of the equation, you can't just add them on to make the equation balanced. Even though it may appear balanced, they have changed the equation when you only need to change the ratios, making the eqn incorrect.

I thought it might of been because of conservation of mass. We can't create nor destroy mass so adding it would be like creating mass?

You cannot add "O" because you would essentially be inputting a different element that isn't actually produced in the chemical reaction. How I like to look at is that adding an extra "+ ___" is never okay.

Celeste 1C wrote:I thought it might of been because of conservation of mass. We can't create nor destroy mass so adding it would be like creating mass?

I think that's the original issue with unbalanced eqns, that there is unequal mass/numbers of elements on both sides, so by balancing them, you make it equal. in the eqn in question, Cu+SO2--> CuO+S, there are 2 "O"s on the left, but only one on the right, so that's what makes it unequal.

Celeste 1C wrote:Question h.1 asks why you can't just add an extra O molecule to balance the equation? Why wouldn't we be able to do that?

I remember that in lecture Dr. Lavelle said that atoms were not created nor destroyed.

adding an O atom would change the composition of the molecule and therefore change the substance

Yes, you can't throw in an extra O atom because of the law of conservation of mass. Instead, manipulate stoichiometric coefficients such that the chemical equation is balanced, or that each side of the equation has the same number of atoms of each element.