Textbook Question
Match the following physical and chemical properties with potassium chloride, KCl, used in salt substitutes, or butane, C4H10 used in lighters:
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a. melts at -138°C
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8. Gases, Liquids and Solids
Intermolecular Forces and Physical Properties
2:59 minutesProblem 2a
Textbook Question
Would you expect the boiling points to increase or decrease in the following series? Explain.
a. Kr, Ar, Ne
Verified step by step guidance1
Identify the trend in the periodic table: Krypton (Kr), Argon (Ar), and Neon (Ne) are all noble gases located in Group 18 of the periodic table. They are arranged in order of increasing atomic number, with Neon being the smallest and Krypton the largest.
Understand the relationship between atomic size and intermolecular forces: As the atomic size increases, the number of electrons also increases. This leads to stronger London dispersion forces (a type of van der Waals force), which are the primary intermolecular forces in noble gases.
Relate intermolecular forces to boiling points: Stronger intermolecular forces require more energy to overcome, resulting in higher boiling points. Therefore, the boiling point is expected to increase as the atomic size increases.
Apply the trend to the given series: Neon (Ne) has the smallest atomic size and weakest London dispersion forces, so it will have the lowest boiling point. Argon (Ar) is larger than Neon, so it will have a higher boiling point. Krypton (Kr) is the largest, so it will have the highest boiling point in the series.
Conclude the trend: The boiling points in the series (Ne, Ar, Kr) are expected to increase as you move from Neon to Krypton due to the increasing strength of London dispersion forces with atomic size.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Noble Gases
Noble gases, including Krypton (Kr), Argon (Ar), and Neon (Ne), are a group of elements characterized by their full valence electron shells, making them largely inert and non-reactive. Their physical properties, such as boiling points, are influenced by their atomic size and intermolecular forces.
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Atomic Size and Boiling Point
The boiling point of a substance is affected by its atomic size and the strength of the intermolecular forces present. In noble gases, larger atoms have more electrons, leading to stronger London dispersion forces, which typically result in higher boiling points as the atomic size increases.
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Trends in the Periodic Table
In the periodic table, boiling points of noble gases increase down the group due to increasing atomic mass and size. As you move from Neon to Argon to Krypton, the atomic size increases, leading to stronger dispersion forces and, consequently, higher boiling points.
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