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1) A gas cylinder that contains helium has an internal volume of 2.24 L. A press

ID: 918815 • Letter: 1

Question

1) A gas cylinder that contains helium has an internal volume of 2.24 L. A pressure gauge attached to the cylinder reads 2070 psi (1 atm = 14.7 psi) at 20.9 °C. What mass of helium is contained in the cylinder?

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2) A 9.55-L container holds a mixture of two gases at 47 °C. The partial pressures of gas A and gas B, respectively, are 0.155 atm and 0.557 atm. If 0.130 mol of a third gas is added with no change in volume or temperature, what will the total pressure become?

Explanation / Answer

1. from idealgas equation

PV = nRT

2.24*(2070/14.7) = (W/4)*0.0821*(20.9+273.15)

W = 52.26 grams.

2.

total pressure of A,B gases = 0.155+0.557 = 0.712 atm

n = no of mol of A,B = PV/RT = 0.712*9.55/(0.0821*320)

   = 0.26 mol

No of mol of C added = 0.13 molv

Total mol of gas mixe r = 0.26+0.13 = 0.39 mol

Total pressure = nRT/V = 0.39*0.0821*320/9.55 = 1.073 atm