For the reaction ? C6H6 + ? O2 → ? CO2 + ? H2O 46.4 grams of C6H6 are allowed to react with 161.1 grams of O2. How much CO2 will be produced by this reaction? Answer in units of grams.

Answer 1

So Hilary L.,

First, balance your reaction. Proceed methodically through the following elements, to set the numbers of atoms on each side of the = to equal values. So, for example, C6H6 = ?CO2 must be 6 CO2, so that the 6 C on the left were exactly accounted for on the right side. OK so Far?

So, here you must proceed in the following order of elements: C, H, O . Note that O must be balanced by adding a coefficient to the left side of the reaction, to the O2. In this reaction, that's the only element that you must deal with in that way. If at any point you reach a reactant or product that seems to require a fractional coefficient, then keep the coefficient there as an integer (such as 1), and bop up the originating material's coefficient appropriately (such as, by increasing it to 2, or 3, etc. as necessary).

For example, if you smelted Fe2O3 to make Fe as a product, immediately you would need to make 2Fe to balance the Fe. But if the reaction were Fe + O2 = Fe2O3 , in this case since there are molecules on the right with 2 Fe's in, you start by making the coefficient of Fe on the left, as 2. So: 2Fe + nO2 = Fe2O3 . That's not completely balanced, because you have that O3 on the right, but only units of O2 in the left. So to balance, you find the least common multiple of O atoms and use it, to get as a next stage: 2Fe + 3O2 = 2Fe2O3 . And you notice that that now your Fe's are unbalanced, so you balance them: 4Fe + 3O2 = 2Fe2O3 .

So, to recapitulate, balance reactions generally in the order of elements: any metals, C, N and other non-metals, H, and O.

Now you know how to do it, time to practice (please, try on your own!)

-- Cheers, -- Mr. d.