Question

If 3.0 moles of A and 4.0 moles of B react according to the hypothetical reaction below, how many moles of the excess reactant will be left over at the end of the reaction? A + 2B → AB2

Answer 1

Answer:

1.0 mol of A should be left over.

Explanation:

We have the balanced equation:

$A+2B=AB_{2}$

That means that I need 1.0 mol of A for each 2.0 moles of B to obtain 1.0 mol of $AB_{2}$

Now, we have 3.0 moles of A and 4.0 moles of B reacting, so:

3.0 moles of A . $\frac{1.0}{1.0}\frac{moles of AB_{2} }{moles of A}$ = 3.0 moles of $AB_{2}$

4.0 moles of B . $\frac{1}{2} \frac{moles of AB_{2}}{moles of B}$ = 2.0 moles of $AB_{2}$

That means that with 3.0 moles of A and 4.0 moles of B, we can form 2.0 moles of $AB_{2}$ and 1.0 mole of A should be left over.

Answer 2

1 mol of A should be left over