Question

If 4.5 moles of X and 5.5 moles of Y react according to the hypothetical reaction below, how many moles of the excess reactant will be left over at the end of the reaction?

2X + 3Y “yields”/ X2Y3

0.8 mol X left over
1.8 mol Y left over
2.3 mol X left over
3.7 mol Y left over

Answer 1

The answer would be 0.8 mol of x left over....
AND THATS IS WHY...refer to the pic below...
See if it is clear enough...

Answer 2

Answer:

0.8 mol X left over

Explanation:

2 moles of X yields 3 moles of Y

4.5 moles of X will yield 3/2 x 4.5 moles of Y  

4.5 moles of X will yield 6.75 moles of Y  

Therefore Y is not in excess

Alternatively,  

3 moles of Y yields 2 moles of X

5.5 moles of Y will yield 2/3 x 5.5 moles of X  

5.5 moles of Y will yield 3.67 moles of X  

Therefore X is in excess. 4.5 - 3.67 = 0.83 moles of X are in excess