Review Pt 2 - Solutions

Review Pt 2 - Solutions - o C), its internal pressure is...

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Use the ideal gas law to show that, for an ideal gas at constant pressure, the coefficient of volume expansion is equal to 1/T. Solution: Assume the pressure and amount of gas are held constant, and so PV = nRT and PV = nRT . From these two expressions calculate the change in volume and relate it to the change in temperature. V = V + Δ V →Δ V = V V = nRT nRT 0 = nR ( T T )= V 0 Δ T But Δ V = β V 0 Δ T ,and so Δ V = (V 0 / T 0 ) Δ T = β V 0 Δ T β = 1/T 0 A helium balloon, assumed to be a perfect sphere, has a radius of 22.0 cm. At room temperature (20
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Unformatted text preview: o C), its internal pressure is 1.06 atm. Determine the number of moles of helium in the balloon, and the mass of helium needed to inflate the balloon to these values. Solution: We find the number of moles of helium in the balloon from the ideal gas equation. PV = nRT n = PV/RT n =( (1.06atm)*(1.013E5Pa)*((4/3)* *(.22m)^3))/((8.314J/mol*K)*293K) = 1.97mol 1.97mol*(4g/1mol H 2 ) = 7.86g...
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