Question

What is the density of N2O a gas at STP?

Answer 1

here is your answer

At STP 1mol oif anything has a volum of 22.4 L

SO the density will be the mass of 1 mol of N2O(~280.1g) divided by 22.4 L


hope you understand

Answer 2

Let's just look at 1 mole of it. 
Density equals mass divided by volume, so we need to find both the mass and the volume. 

The volume of 1 mole of any gas at STP is 22.4 liters. 
The mass of 1 mole of N2O = 2 * 14 + 16 = 44 grams. 

Thus, its density is roughly 44/22 = 2 grams / liter