Which evaporates more quickly: 100 mL of water (H 2 O) in a beaker or 100 mL of acetone [(CH 3 ) 2 CO] in an identical beaker under identical conditions? Is the vapor pressure of the two substances different? Explain.

hey everyone in this example, we need to identify which of the below substances will evaporate faster in identical conditions and amounts. So what we want to recall is a concept of vapor pressure and we should recall that compounds with stronger inter molecular forces will have lower vapor pressure. And that therefore means that we have more energy that is required two separate the particles. So we should recognize that our first compound, which we recognize as benzene just consists of carbon and hydrogen. So we would recognize this as a hydrocarbon. We also want to recognize that because we have six carbons and six hydrogen in this molecule, we have a symmetrical molecule. And so therefore this is going to be a non polar molecule, meaning that the only inter molecular force present is therefore going to be our London dispersion inter molecular force. And because we recall that this is going to be a weaker inter molecular force. This will correspond to a higher value for vapor pressure for our compound benzene. So now we want to consider our next molecule, Which we would recognize as one Pen Tunnel. So we want to identify that within this molecule, we have specifically oxygen bonded to hydrogen, where oxygen is a non metal to the other nonmetal hydrogen. And because we have this specific bond here, this signals that we have the inter molecular force hydrogen bonding occurring or present. And so this is holding our particles in our one pentagonal together. And because we recall that hydrogen bonding is one of our stronger inter molecular forces which is much stronger than London dispersion forces. As we saw in benzene, we can say that this will correspond to a lower vapor pressure. So overall we can say that the vapor pressure of benzene, Sorry, that should be C6 is greater than the vapor pressure of our one pen tunnel C five H 12 0. H. And so therefore, benzene will evaporate faster. And so for our final answer, we have this explanation here that I've outlined. So if you have any questions, please leave them down below. Otherwise, I will see everyone in the next practice video.

Ch.12 - Liquids, Solids & Intermolecular Forces

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Tro 6th Edition

Ch.12 - Liquids, Solids & Intermolecular Forces

Problem 58

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Chapter 12, Problem 58

Which evaporates more quickly: 100 mL of water (H₂O) in a beaker or 100 mL of acetone [(CH₃)₂CO] in an identical beaker under identical conditions? Is the vapor pressure of the two substances different? Explain.

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Identify the substances involved: water (H_2O) and acetone ((CH_3)_2CO).

Understand that evaporation rate is influenced by vapor pressure; higher vapor pressure means faster evaporation.

Research the vapor pressures of water and acetone at the same temperature. Acetone generally has a higher vapor pressure than water.

Explain that because acetone has a higher vapor pressure, it will evaporate more quickly than water under identical conditions.

Conclude that the vapor pressures of water and acetone are different, with acetone having a higher vapor pressure, leading to faster evaporation.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Vapor Pressure

Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid or solid phase at a given temperature. It reflects the tendency of particles to escape from the liquid into the vapor phase. Substances with higher vapor pressures evaporate more quickly because more molecules have enough energy to overcome intermolecular forces and enter the gas phase.

Intermolecular Forces

Intermolecular forces are the forces of attraction or repulsion between neighboring particles (atoms, molecules, or ions). These forces significantly influence a substance's boiling point and evaporation rate. Water, with strong hydrogen bonds, has higher intermolecular forces compared to acetone, which has weaker dipole-dipole interactions and London dispersion forces, leading to faster evaporation of acetone.

Evaporation Rate

The evaporation rate is the speed at which molecules transition from the liquid phase to the vapor phase. It is influenced by factors such as temperature, surface area, and vapor pressure. In this scenario, acetone is expected to evaporate more quickly than water due to its lower boiling point and weaker intermolecular forces, despite both being in identical conditions.

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