Consider the equation 2a plus b--a2b if you mix 1.0 mol of a and 1.0 mol of b how many moles of a2b can be produced?

Answer 1

Because it takes 2a to make 1mol of a2b, the ratio is 1mol a2b/2mol a. If you only have 1.0 mol of a to react, then 1mol a x (1mol a2b/2 mol a)= 0.5 mol of a2b

Because it takes 1 mol of b to make 1 mole of a2b, the ratio is 1mol a2b/1mol b. So, 1.0 mol b x (1mol a2b/1mol b)= 1.0 mol of a2b.

Since you run out of a to react with b, a is the limiting reagent meaning that you can only produce 0.5 mol of a2b even though you have an excess amount of b. So, only 0.5 mol of a2b can be produced.