Question

Consider Krypton. What is its density at 20oC and 0.993 bar? What is its average speed in km/hour? If 5.00 g of krypton is put into an empty balloon at 20oC and 0.993 atm, what is the volume of the balloon? Do you expect the balloon to rise or sink? Why?

Answer 1

Using,

PV = nRT

n = g/molar mass

P = (g/V)RT/molar mass

density = P x molar mass/RT

with,

P = 0.993 bar = 0.98 atm

R = gas constant

T = 20 + 273 = 293 K

molar mass = 83.8 g/mol

we get,

density of krypton = 0.98 x 83.8/0.08206 x 293 = 3.41 g/L

Average speed = sq.rt.(3RT/M)

                         = sq.rt.(3 x 8.31447 x 297/0.0838)

                         = 87212.639 m/s = 313965.5 km/h

If 5 g kryton is put in balloon

moles of krypton = 5/83.8 = 0.06 mol

Volume of balloon = nRT/P = 0.06 x 0.08206 x 293/0.098 = 1.47 L

Krpton is dense, and thus the balloon with krypton will sink.