Question

The ideal gas law describes the relationship among the volume of an ideal gas (V), its pressure (P), its absolute temperature (T), and number of moles (n):

PV=nRT

Under standard conditions, the ideal gas law does a good job of approximating these properties for any gas. However, the ideal gas law does not account for all the properties of real gases such as intermolecular attraction and molecular volume, which become more pronounced at low temperatures and high pressures. The van der Waals equation corrects for these factors with the constants a and b, which are unique to each substance:

(P+an2V2)(V−nb)=nRT

The gas constant R is equal to 0.08206 L⋅atm/(K⋅mol).

Part A

A 3.00-L flask is filled with gaseous ammonia, NH3. The gas pressure measured at 20.0 ∘C is 2.55 atm . Assuming ideal gas behavior, how many grams of ammonia are in the flask?

Express your answer to three significant figures and include the appropriate units.

Part B

If 1.00 mol of argon is placed in a 0.500-L container at 25.0 ∘C , what is the difference between the ideal pressure (as predicted by the ideal gas law) and the real pressure (as predicted by the van der Waals equation)? For argon, a=1.345(L2⋅atm)/mol2 and b=0.03219L/mol.

Express your answer to two significant figures and include the appropriate units.

Answer 1