A little help? No idea what to do here?

Question

If 4.50 mol of ethane, C2H6, undergo combustion according to the unbalanced equation C2H6+O2--->CO2+H2O, How many moles of oxygen are required?
b. How many moles of each product are formed?

Answer 1

First, you need to balance the equation:

At first it looks like:

C2H6 + x O2 ---> 2 CO2 + 3 H2O

But this won't work as you would need 3 1/2 oxygen molecules, to make it add up; so double everything and then you can make it balance with no "odd" oxygens.

2 C2H6 +7 O2 ----> 4 CO2 + 6 H2O

Now you can get the other answers. You have 4.5 moles of the starting material ethane; the amount of products of each kind formed will be in the ratios of the balanced equation, so:

For moles of oxygen needed: 4.5 x (7/2) = 15.75moles O2
For CO2 formed; 4.50 x (4/2) = 9.0 moles CO2
For H2O formed; 4.50 x (6/2) = 13.50 moles H2O