# What is the mass in grams contained in 99.02 L of NO2 at STP?

##### 1 Answer

The answer is

At STP - Standard Temperature and Pressure (273.15K, 1 atm) - an ideal gas' molar volume is equal to **any ideal gas** always occupies that volume at that pressure and that temperature.

Now, even before calculating the actual value, one must try and estimate what that value could be; since we were given

SInce 22.4 is between 4 and 5 times smaller (more than 4, less than 5) than 99.02, we could estimate the number of moles to be 4.5, which, given

The actual number of moles is

Notice the similarity between the estimate and the actual result...