Dry ice is solid carbon dioxide; it vaporizes at room temperature and normal pre

Question

Dry ice is solid carbon dioxide; it vaporizes at room temperature and normal pressures to the gas. Suppose you put 32.3 g of dry ice in a vessel fitted with a piston, and it vaporizes completely to the gas, pushing the piston upward until its pressure and temperature equal those of the surrounding atmosphere at 17.6 °C and 751 mm Hg. Calculate the work done by the gas in expanding against the atmosphere. Neglect the volume of the solid carbon dioxide, which is very small in comparison to the volume of the gas phase.

Explanation / Answer

No of moles of CO2 = 32.3/44 = 0.734 mole.

so that,

volume of gas = V = nRT/P

P = 751 MMhg = 0.98816 Atm

R = 0.0821 l.atm.k-1.mol-1

T = 17.6 °C = 290.6

n = 0.734 mole

V = 0.734*0.0821*290.6/0.98816 = 17.72 L

isotherma irreversible work done = PDV

P = 751 MMhg = 0.98816 Atm

DV = V2-v1

v2 = final volume = 17.72 l

V1 = initial volume = 0 l

DV = 17.72 L

w = -0.98816*17.72 = -17.51 l.atm

1 l.atm = 101.2 joule

w = -17.51*101.2 = -1.772 kj

work done by the gas= -1.772 kj

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