Answer : The mass of
added must be, 61.9 grams
Explanation : Given,
Mass of
= 40 g
Molar mass of
= 105.9 g/mol
First we have to calculate the moles of
.

Now we have to calculate the moles of 
The balance chemical reaction will be:

From the balanced reaction we conclude that
As, 1 mole of
react with 1 mole of 
So, 0.378 mole of
react with 0.378 mole of 
Now we have to calculate the mass of 

Molar mass of
= 164 g/mol

Thus, the mass of
added must be, 61.9 grams