P2) One can make a âdry ice bombâ bydropping a chip of dry ice(solid CO2) into a
plastic 2-liter bottle of warm water and sealing the cap.TheCO2 sublimates into gas, and
the gas pressure eventually blows the bottleapart.
Suppose that the 2.00-liter bottle is preciselythree-quartersfull, and the temperature of
the bottle is kept at room temperature (297 K). 22 gramsof dryice are added to the
bottle, and then the bottle is sealed up, so the numberofmoles of CO2 is constant, as is
the total volume of the bottle.
To solve this problem realistically, we need to takeintoaccount the fact that some of the
gas is dissolved in the water. This is described by alaw ofchemistry called Henryâs
Law, which states:
H d
k n
p
V
=
where p is the partial pressure of the CO2 gas, nd = numberofmoles of gas dissolved in
the water, and V is the volume of the water. For CO2 inwaterat room temperature, the
constant kH = 29.4 L atm/mol.
(a) Calculate the final pressure of the gas (inatmospheres)when all the CO2 sublimates,
assuming, as you did in Recitation, that you can ignoretheheat capacity of the gases.
(b) Repeat the calculation in (a), but do NOT ignore theheatcapacity of the gases. Was
our âignore the gasesâ assumption a goodone?