Answer : The mass of
required is 71.175 grams.
Explanation :
To calculate the moles of nitrogen gas, we use the equation given by ideal gas :
PV = nRT
where,
P = Pressure of nitrogen gas = 763 torr
V = Volume of the nitrogen gas = 40.0 L
n = number of moles of gas = ?
R = Gas constant = 
T = Temperature of helium gas = 
Putting values in above equation, we get:

Now we have to calculate the moles of
.
The balanced chemical reaction is:

From the balanced chemical reaction, we conclude that
As, 3 moles of
produced from 2 moles 
So, 1.642 moles of
produced from
moles 
Now we have to calculate the mass of
.
Molar mass of
= 65 g/mol


Therefore, the mass of
required is 71.175 grams.