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steringPhysics Homework a2 Google Chrome ecure l https/lsession.masteringphysics

ID: 1524546 • Letter: S

Question

steringPhysics Homework a2 Google Chrome ecure l https/lsession.masteringphysics.com/myct/itemview?assignmentProblemID 73835678&offset; next Y 2049 801 Spring 2017 mework Exercise 18.8 xercise 18.8 Part A A welder using a tank of volume 7.60x10-2 m2 fills i with Find the initial mass of oxygen. oxygen (with a molar mass of 32.0 g/mol) at a gauge pressure of 3.30x105 Pa and temperature of 35.5 C The tank has a small leak, and in time some of the oxygen leaks on a day when the temperature is 21.0 C the gauge pressure of the oxygen in the tank is 200 105 Pa Submit My Answers Give Up Part B Find the mass of oxygen that has leaked out Submit

Explanation / Answer

(a). Volume V = 7.6x10 -2 m 3

Molar mass M = 32 g / mol

Gauge pressure P = 3.3x10 5 Pa

Absolute pressure P ' = Po + P

       P ' = (1.01x10 5 ) +(3.3x10 5 Pa)

            = 4.31x10 5 Pa

From the relation P 'V = nRT

Number of moles n = P ' V / RT    Where T = Absolute temperature = 35.5 o C = 35.5+273 = 308.5 K

                             = (4.31x10 5 )(7.6x10 -2) /(8.314)(308.5)

                             = 12.771 mol

Initial mass of oxygen m = n M

                                     = 12.771 (32 )

                                     = 408.68 g

(b). Volume V = 7.6x10 -2 m 3

Molar mass M = 32 g / mol

Gauge pressure P = 2x10 5 Pa

Absolute pressure P ' = Po + P

       P ' = (1.01x10 5 ) +(2x10 5 Pa)

            = 3.01x10 5 Pa

From the relation P 'V = n ' RT '

Number of moles n ' = P ' V / RT    Where T ' = Absolute temperature = 21 o C = 21+273 = 294 K

                             = (3.01x10 5 )(7.6x10 -2) /(8.314)(294)

                             = 9.3588 mol

Final mass of oxygen m ' = n ' M

                                     = 9.3588 (32 )

                                     = 299.78 g