Chlorofluorocarbons, or CFCs, were used for many years as aerosol propellants (S

Question

Chlorofluorocarbons, or CFCs, were used for many years as aerosol propellants (Section 7.4). Although CFCs, such as CFC-12, are gases at normal pressure, under high pressures they can be converted into a liquid. The liquid CFC in an aerosol canister evaporates, and the resulting vapor pressure pushes substances out of the canister. When the valve on the top of the canister is pressed and chemical substances escape, the pressure inside the canister decreases at first, but it quickly returns to the pressure that existed before the valve was pushed. Describe what happens at the "submicroscopic" level as the pressure returns to its original value. Why does the pressure return to the same value as long as any liquid CFC remains in the canister? If you were looking for a replacement for CFCs in aerosol canisters, what are the criteria you might consider?

Explanation / Answer

At the submicroscopic level, there exists an equillibrium between CFC(l) and CFC (g).

CFC (l) <->CFC(g)

As CFC (l) in the canister evaporates it generates significant gas pressure within the canister. If the gas does not escape, there will be an equillibrium between the (l) and (g) forms. However, because the gas escapes the canister, the equilibrim shifts towards the right i.e towards more CFC (g) formation (following the LeChatlier's principle) which would again escape from the canister until all of the liquid evaporates into gas.

A more suitable liquid would be the one which has a lower vapor pressure such that the vapour cannot escape from the canister.

Related Questions

Navigate

• Browse (All)
• Browse C
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.