Which evaporates more quickly: 55 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.11 - Liquids, Solids & Intermolecular Forces

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Tro 4th Edition

Ch.11 - Liquids, Solids & Intermolecular Forces

Problem 54

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Chapter 11, Problem 54

Which evaporates more quickly: 55 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 key factors that affect evaporation: surface area, temperature, and vapor pressure. Since the beakers are identical and conditions are the same, focus on vapor pressure.

Understand that vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid phase at a given temperature.

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

Explain that a higher vapor pressure indicates that a substance evaporates more readily because more molecules have enough energy to escape the liquid phase.

Conclude that acetone, with its higher vapor pressure, will evaporate more quickly than water under identical conditions.

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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 indicates how readily a substance will evaporate; higher vapor pressure means a substance evaporates more quickly. Water and acetone have different vapor pressures due to their molecular structures and intermolecular forces, affecting their evaporation rates.

Intermolecular Forces

Intermolecular forces are the forces of attraction or repulsion between molecules. They play a crucial role in determining the physical properties of substances, including boiling points and evaporation rates. Water has strong hydrogen bonding, while acetone has weaker dipole-dipole interactions, leading to acetone evaporating more quickly than water under identical conditions.

Evaporation Rate

The evaporation rate is the speed at which molecules transition from the liquid phase to the vapor phase. Factors influencing evaporation include temperature, surface area, and intermolecular forces. In this scenario, acetone, with its lower boiling point and weaker intermolecular forces, will evaporate more quickly than water, despite the volume differences.