Question

When sodium azide is activated in an automobile airbag, nitrogen gas and sodium are produced according to the following equation: 2NaN3(s) ⟶ 2Na(s) + 3N2(g) If 0.500 mol NaN3 react, what mass in grams of nitrogen would result?
A) 21.0 g N2
B) 20.0 g N2
C) 19.0 g N2
D) 12.0 g N2

Answer 1

Answer:
A) 21.0 g of N2

Explanation:
From the periodic table:
atomic mass of nitrogen = 14 grams
This means that:
molar mass of N2 = 2(14) = 28 grams/mole

Now, from the given balanced equation, 2 moles of NaN3 produce 3 moles of N2. We can use cross multiplication to know the number of moles of N2 produced from 0.5 moles of NaN3 as follows:
2 moles NaN3 ..............> 3 moles N2
0.5 moles NaN3 ...........> ?? moles N2
number of moles of N2 = (0.5*3) / 2 = 0.75 moles

Now, we will get the mass of 0.75 moles as follows:
number of moles = mass / molar mass
mass = number of moles * molar mass
mass = 0.75 * 28
mass = 21 grams

Hope this helps :)