etap29 ±Ideal versus Real Gases Ideal versus Real Gases The ideal gas law descri

Question

etap29 ±Ideal versus Real Gases Ideal versus Real Gases 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 ( 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 lovw temperatures and high pressures. The van der Waals equation corrects for these factors with the constants and &, which are unique to each substance: The gas constant R is equal to 0.08206 L-atm/K Part A A 3.00-L flask is filled with gaseous ammonia, NH, The gas pressure measured at 28.0 cis 1.55 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. Hints mass of NHH Value Units Submit My Answers Give Up Ideal versus real behavior for gases In the following part you can see how the behavior of real gases deviates from the ideal behavior You will calculate the pressure values for a gas using the ideal gas law and also the van der Waals equation. Take note of how they differ Part B If 1.00 mol of argon is placed in a 0.500-L container at 30.0c, 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, -1.345 (L, atm/rnol, and b-am19L, Express your answer to two significant figures and include the appropriate units Hints nk"-R-1 Value Units Submit My Answers Give Up

Explanation / Answer

A)

ideal gas:

PV = nRt

n = PV/(RT)

n = (1.55*3)/(0.082*(28+273))

n = 0.188396

mass of NH3 = mol*MW = 0.188396*17 = 3.2027 g of NH3

B)

difference:

PV = nRT

Pideal = nRT/V = (1*0.082*(30+273)/(0.5) = 49.692 atm

now, Preal:

The Van der Waals equation is a description of real gases, it includes all those interactions which we previously ignore in the ideal gas law.

It considers the repulsion and collision, between molecules of gases. They are no longer ignored and they also are not considered a"point" particle.

The idel gas law:

PV = nRT

P(V/n) = RT ; let V/n = v; molar volume

P*v = RT

now, the van der Waals equation corrects pressure and volume

(P+ a/v^2) * (v - b) = RT

where;

R = idel gas law; recommended to use the units of a and b; typically bar/atm and dm/L

T = absolute temperature, in K

v = molar volume, v = Volume of gas / moles of gas

P = pressure of gas

Knowing this data; we can now substitute the data

given

a = 3.6551

b = 0.04281

(P+ a/v^2) * (v - b) = RT

v = V/n = 0.5/1 = 0.5

Preal = RT/(v-b) - a/V^2

Preal = 0.082*(30+273)/(0.5-0.03219) - 1.345/(0.5^2)

Preal = 47.7313

Pideal - Preal = 49.692 -47.7313 = 1.9607 atm

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