Answer : The excess reactant is, 
The leftover amount of excess reagent is, 7.2 grams.
Solution : Given,
Mass of
= 105.0 g
Mass of
= 78.0 g
Molar mass of
= 80.11 g/mole
Molar mass of
= 18 g/mole
Molar mass of
= 100.09 g/mole
First we have to calculate the moles of
and
.


Now we have to calculate the limiting and excess reagent.
The balanced chemical reaction is,

From the balanced reaction we conclude that
As, 1 mole of
react with 3 mole of 
So, 1.31 moles of
react with
moles of 
From this we conclude that,
is an excess reagent because the given moles are greater than the required moles and
is a limiting reagent and it limits the formation of product.
Left moles of excess reactant = 4.33 - 3.93 = 0.4 moles
Now we have to calculate the mass of excess reactant.


Thus, the leftover amount of excess reagent is, 7.2 grams.