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

1 mol of A should be left over

Answer 2

1.0 mol of A should be left over.

Step-by-step 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 .
`(1.0)/(1.0)(moles of AB_(2) )/(moles of A)` = 3.0 moles of
`AB_(2)`

4.0 moles of B .
`(1)/(2) (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.