148,276 views
30 votes
30 votes
A sample of liquid ethanol is added to a sealed glass beaker.A sealed beaker contains liquid ethanol, represented as circles. Most of the circles are in the liquid, but a few are in the space above the liquid.Figure © 2019 StrongMindBeaker: BlueRingMedia/ShutterstockWhat will happen to the ethanol after a minute?

A sample of liquid ethanol is added to a sealed glass beaker.A sealed beaker contains-example-1
User Stefan Haberl
by
2.6k points

1 Answer

17 votes
17 votes

We don't have information about how fast the equilibrium will be reached, however, we can analyze the options to see which ones are wrong.

What in fact happens is that the system's previous conditions doesn't matter much. After it is sealed, there is no way something gets out. At first, the system will not be at an equilibrium, it needs some time for that.

The system will have ethanol gas condensating and liquid ethanol evaporating, but at different rates.

Assuming the rate of evaporation is higher at the beginning, we will get more ethanol gas with time, but this will decrease the rate of evaporation a situation where both rates are equal. After that point, the system will be at equilibrium, meaning the amount of liquid and gas won't change anymore.

Having that in mind, the first alternative have the first part wront because the system nees time to get to equilibrium, but its second part is wrong too, because as we said the system will eventually stop getting more ethanol gas.

The second is wrong because both evaporating and condensation are happening at the same time, not one after the other.

The third is wrong because it wil always have an equilibrium. If all ethanol condensates, the rate of condensation will be zero and any evaporation that happens will make some ethanol gas back.

We can't know for sure that 1 minute will be enough to reach the equilibrium, but assuming it is, the fourth alternative perfectly describes what is happening: ethanol condensates and increase the pressure up to a point where both rates equilizes and the system reach the equilibrium.

So, the correct option is the fourth alternative.

User Wewlie
by
3.2k points