Question

Calculate the expansion work done against a constant external pressure of 0.995 atm and at a constant temperature of 19°C. Assume that the initial volume of dry ice is negligible and that CO2 behaves like an ideal gas.

Answer 1

This is an incomplete question, here is a complete question.

A 19.2 g quantity of dry ice (solid carbon dioxide) is allowed to sublime (evaporate) in an apparatus. Calculate the expansion work done against a constant external pressure of 0.995 atm and at a constant temperature of 22 degrees C. Assume that the initial volume of dry ice is negligible and that CO₂ behaves like an ideal gas.

Answer : The expansion work done is, -1058.33 J

Explanation :

First we have to calculate the volume of gas.

Using ideal gas equation:

`PV=nRT\\\\PV=(w)/(M)RT`

where,

P = pressure of gas = 0.995 atm

Conversion used : (1 atm = 760 torr)

V = volume of gas = ?

T = temperature of gas =
`19^oC=273+19=292K`

R = gas constant = 0.0821 L.atm/mole.K

w = mass of gas = 19.2 g

M = molar mass of carbon dioxide gas = 44 g/mole

Now put all the given values in the ideal gas equation, we get:

`(0.995atm)* V=(19.2g)/(44g/mole)* (0.0821L.atm/mole.K)* (292K)`

`V=(19.2g)/(44g/mole)* ((0.0821L.atm/mole.K)* (292K))/(0.995atm)`

`V=10.5L`

Now we have to calculate the work done.

Formula used :

`w=-p\Delta V`

where,

w = work done

p = pressure of the gas = 0.995 atm

`\Delta V` = volume = 10.5 L

Now put all the given values in the above formula, we get:

`w=-p\Delta V`

`w=-(0.995atm)* (10.5L)`

`w=-10.4475L.atm=-10.4475* 101.3J=-1058.33J`

conversion used : (1 L.atm = 101.3 J)

Thus, the expansion work done is, -1058.33 J