Answer:
To do this question. we first have to find the mass% of nitrogen in N2O and then, using that percentage, we can simply find the number of moles of N from the number of moles of N2O
Mass % of Nitrogen:
Mass% of nitrogen = (Molar mass of N2 / Molar mass of N2O)*100
Mass% nitrogen = (28 / 44)*100
Mass% of Nitrogen = 0.63 * 100
Mass% nitrogen = 63%
Mass of Nitrogen:
So, now we can say that in any given mass of N2O. 63% of the total mass is the mass of Nitrogen
Hence, total mass * 63/100 = Mass of Nitrogen
Replacing the variables
40 * 0.63 = Mass of Nitrogen
Mass of Nitrogen = 25.2 grams