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(Ch. 19) A storage tank at standard temperature and pressure (STP) defined as T

ID: 1303528 • Letter: #

Question

(Ch. 19) A storage tank at standard temperature and pressure (STP) defined as T = 0 degreeC and P = 1 atm = 105 pa, contains 24.5kg of nitrogen gas (N2), which can be treated as idea gas (a) What is the volume of the tank? (b) If an additional 24.5 kg of nitrogen is then added, when is the new pressure inside the tank, assuming everything else remains the same? (Note the molar mass of nitrogen gas is 0.028 kg/mol) (Ch.20) In a certain steam engine, the boiler temperature is 127 degreeC and the cold reservoir temperature is 27 degreeC. (a) Assuming the engine is ideal (or reversible), what is its efficiency? reservoir?

Explanation / Answer

3. Given: T=0? =273K

Pressure=1atm

Mass of N2=24.5kg

Moles of N2, n=24.5/28=0.875 kmol

a.Volume of flask= nRT/P

=0.875*103*0.0821*273/1

=19611 ltr

=19.611 m3

b.Now, final mass=24.5+24.5=49 kg

Moles =1.750 kmol

Pressure, P= nRT/V

=1.750*103*0.0821*273/19611

=2atm

20. For heat engine,

TC=27?=300K

TH=127?=400K

a.Efficiency, ?=1-TC/TH

=1-300/400=0.25=25%

b.Amount into cold reservoir=work done*[1-efficiency]/efficiency

=8.34*[1-0.25]/0.25

=25.02 kJ