(a) Place the following substances in order of increasing volatility: CH 4 , CBr 4 , CH 2 Cl 2 , CH 3 Cl, CHBr 3 , and CH 2 Br 2 . (b) How do the boiling points vary through this series? (c) Explain your answer to part (b) in terms of intermolecular forces.

Hey everyone, we're asked to consider the following compounds and to arrange in order of increasing volatility and to briefly explain our answer. Now, looking at these compounds, we can see that they are all non polar substances, which means that the inter molecular force present here is going to be our London dispersion forces. Now, how does this relate to volatility? Well, we know that if a compound is more volatile, this means that it has weaker London dispersion forces. So in order to answer this question, we need to look at the strength of our inner molecular forces and in this case it will be our London dispersion forces. So to compare the strength, we will have to look at the molecular weight of each compound and the relation to this is that the smaller the molecular weight, the weaker our London dispersion forces are going to be Now in comparison to a larger molecular weight. This means our London dispersion forces are going to be stronger and that is because we have a more polarized able electron cloud. Now to arrange this in order of increasing volatility, the one that will be the least volatile will have the strongest London dispersion forces, which means it will have the largest molecular weight in this case it'll be carbon tetra I died followed by carbon tetra bromide. Next we will have carbon tetrachloride followed by carbon tetra fluoride. And lastly with the weakest London dispersion forces is going to be our methane and this is going to be our final answer. Now, I hope that made sense. And let us know if you have any questions.

Ch.11 - Liquids and Intermolecular Forces

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Brown 14th Edition

Ch.11 - Liquids and Intermolecular Forces

Problem 51

Chapter 11, Problem 51

(a) Place the following substances in order of increasing volatility: CH₄, CBr₄, CH₂Cl₂, CH₃Cl, CHBr₃, and CH₂Br₂. (b) How do the boiling points vary through this series? (c) Explain your answer to part (b) in terms of intermolecular forces.

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Identify the types of intermolecular forces present in each substance: CH_4, CBr_4, CH_2Cl_2, CH_3Cl, CHBr_3, and CH_2Br_2. Consider London dispersion forces, dipole-dipole interactions, and hydrogen bonding.

Recognize that volatility is inversely related to the strength of intermolecular forces. Substances with weaker intermolecular forces are more volatile.

Arrange the substances in order of increasing volatility by comparing the strength of their intermolecular forces. Consider molecular weight and polarity.

For boiling points, note that they are directly related to the strength of intermolecular forces. Substances with stronger intermolecular forces have higher boiling points.

Explain the variation in boiling points by discussing the role of molecular weight and polarity in determining the strength of London dispersion forces and dipole-dipole interactions.

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Key Concepts

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

Volatility

Volatility refers to the tendency of a substance to vaporize. It is influenced by the strength of intermolecular forces; substances with weaker forces tend to be more volatile. For example, lighter molecules with weaker London dispersion forces will evaporate more readily than heavier molecules with stronger dipole-dipole interactions or hydrogen bonds.

Boiling Point

The boiling point of a substance is the temperature at which its vapor pressure equals the external pressure, allowing it to transition from liquid to gas. Generally, higher boiling points indicate stronger intermolecular forces. In the context of the given substances, as molecular weight and polarity increase, boiling points typically rise due to enhanced van der Waals forces.

Intermolecular Forces

Intermolecular forces are the forces of attraction or repulsion between molecules. They include London dispersion forces, dipole-dipole interactions, and hydrogen bonds. The type and strength of these forces significantly affect both volatility and boiling points; for instance, substances with stronger intermolecular forces will have lower volatility and higher boiling points compared to those with weaker forces.

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Related Practice

Textbook Question

The critical temperatures and pressures of a series of halogenated methanes are as follows:

(a) List the intermolecular forces that occur for each compound.

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Textbook Question

The critical temperatures and pressures of a series of halogenated methanes are as follows: (c) Predict the critical temperature and pressure for CCl4 based on the trends in this table. Look up the experimentally determined critical temperatures and pressures for CCl4, using a source such as the CRC Handbook of Chemistry and Physics, and suggest a reason for any discrepancies.

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Open Question

Which of the following affects the vapor pressure of a liquid? (a) Volume of the liquid, (b) surface area, (c) intermolecular attractive forces, (d) temperature, (e) density of the liquid

Open Question

True or false: (a) CBr4 is more volatile than CCl4. (b) CBr4 has a higher vapor pressure at the same temperature than CCl4.

Textbook Question

(a) Two pans of water are on different burners of a stove. One pan of water is boiling vigorously, while the other is boiling gently. What can be said about the temperature of the water in the two pans?

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Textbook Question

You are high up in the mountains and boil water to make some tea. However, when you drink your tea, it is not as hot as it should be. You try again and again, but the water is just not hot enough to make a hot cup of tea. Which is the best explanation for this result? (a) High in the mountains, it is probably very dry, and so the water is rapidly evaporating from your cup and cooling it. (b) High in the mountains, it is probably very windy, and so the water is rapidly evaporating from your cup and cooling it. (c) High in the mountains, the air pressure is significantly less than 1 atm, so the boiling point of water is much lower than at sea level. (d) High in the mountains, the air pressure is significantly less than 1 atm, so the boiling point of water is much higher than at sea level.

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(a) Place the following substances in order of increasing volatility: CH4, CBr4, CH2Cl2, CH3Cl, CHBr3, and CH2Br2. (b) How do the boiling points vary through this series? (c) Explain your answer to part (b) in terms of intermolecular forces.

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Verified Solution

Key Concepts

Volatility

Boiling Point

Intermolecular Forces

(a) Place the following substances in order of increasing volatility: CH₄, CBr₄, CH₂Cl₂, CH₃Cl, CHBr₃, and CH₂Br₂. (b) How do the boiling points vary through this series? (c) Explain your answer to part (b) in terms of intermolecular forces.