Log out Go to App
Go to App

Learning Materials

Features

Discover

Chapter 8: Problem 25

Consider the ionic compounds KF, NaCl, NaBr, and LiCl. (a) Use ionic radil (Figure 7.8) to estimate the cation-anion distance for each compound. (b) Based on your answer to part (a), arrange these four compounds in order of decreasing lattice energy. (c) Check your predictions in part (b) with the experimental values of lattice energy from Table \(8.1 .\) Are the predictions from ionic radii correct?

Short Answer

Expert verified
The cation-anion distances for KF, NaCl, NaBr, and LiCl are 252 pm, 264 pm, 279 pm, and 227 pm respectively. Based on these distances, the order of decreasing lattice energy is LiCl, KF, NaCl, and NaBr. This order is confirmed by the experimental lattice energy values from Table 8.1: LiCl (853 kJ/mol), KF (821 kJ/mol), NaCl (787 kJ/mol), and NaBr (747 kJ/mol). Thus, the predictions based on ionic radii are correct.

Step by step solution

01

Calculate the cation-anion distances for each compound

For each compound, add the ionic radii of the cation and anion to find the cation-anion distance. Use Figure 7.8 to find the ionic radii. For KF: - K⁺ radius: 133 pm - F⁻ radius: 119 pm Cation-anion distance = 133 pm + 119 pm = 252 pm For NaCl: - Na⁺ radius: 97 pm - Cl⁻ radius: 167 pm Cation-anion distance = 97 pm + 167 pm = 264 pm For NaBr: - Na⁺ radius: 97 pm - Br⁻ radius: 182 pm Cation-anion distance = 97 pm + 182 pm = 279 pm For LiCl: - Li⁺ radius: 60 pm - Cl⁻ radius: 167 pm Cation-anion distance = 60 pm + 167 pm = 227 pm
02

Arrange compounds in order of decreasing lattice energy

Lattice energy is inversely proportional to the distance between the cation and anion. Smaller cation-anion distance results in stronger attractive forces and thus higher lattice energy. Using the cation-anion distance found above, we can arrange the compounds in order of decreasing lattice energy: 1. LiCl (227 pm) 2. KF (252 pm) 3. NaCl (264 pm) 4. NaBr (279 pm)
03

Compare the predicted order with experimental values

Now, let's compare our prediction with the experimental values of lattice energy from Table 8.1. The lattice energies (in kJ/mol) for the compounds are: - KF: 821 kJ/mol - NaCl: 787 kJ/mol - NaBr: 747 kJ/mol - LiCl: 853 kJ/mol Based on the experimental values, the order of decreasing lattice energy is: 1. LiCl (853 kJ/mol) 2. KF (821 kJ/mol) 3. NaCl (787 kJ/mol) 4. NaBr (747 kJ/mol) This confirms that our predictions based on ionic radii are indeed correct.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Start your free trial

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Some chemists believe that satisfaction of the octet rule should be the top criterion for choosing the dominant Lewis structure of a molecule or ion. Other chemists believe that achieving the best formal charges should be the top criterion. Consider the dihydrogen phosphate ion, \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\) , in which the \(\mathrm{H}\) atoms are bonded to \(\mathrm{O}\) atoms. (a) What is the predicted dominant Lewis structure if satisfying the octet rule is the top criterion? (b) What is the predicted dominant Lewis structure if achieving the best formal charges is the top criterion?

A common form of elemental phosphorus is the tetrahedral \(\mathrm{P}_{4}\) molecule, where all four phosphorus atoms are equivalent: At room temperature phosphorus is a solid. (a) Are there any lone pairs of electrons in the \(\mathrm{P}_{4}\) molecule? (b) How many \(\mathrm{p}-\mathrm{p}\) bonds are there in the molecule? (c) Draw a Lewis structure for a linear \(P_{4}\) molecule that satisfies the octet rule. Does this molecule have resonance structures? (d) On the basis of formal charges, which is more stable, the linear molecule or the tetrahedral molecule?

Ammonium chloride, \(\mathrm{NH}_{4} \mathrm{Cl},\) is a very soluble salt in water. (a) Draw the Lewis structures of the ammonium and chloride ions. (b) Is there an \(\mathrm{N}-\) Cl bond in solid ammonium chloride? (c) If you dissolve 14 gof ammonium chloride in 500.0 \(\mathrm{mL}\) of water, what is the molar concentration of the solution? (d) How many grams of silver nitrate do you need to add to the solution in part (c) to precipitate all of the chloride as silver chloride?

Predict the ordering, from shortest to longest, of the bond lengths in \(\mathrm{CO}, \mathrm{CO}_{2},\) and \(\mathrm{CO}_{3}^{2-}\) .

Use Lewis symbols and Lewis structures to diagram the formation of \(\mathrm{PF}_{3}\) from \(\mathrm{P}\) and \(\mathrm{F}\) atoms, showing valence- shell electrons. (a) How many valence electrons does P have initially? (b) How many valence electrons does each F have initially? ( c) How many valence electrons surround the Pin the PF_ \(_{3}\) molecule? (d) How many valence electrons surround each \(\mathrm{F}\) in the \(\mathrm{PF}_{3}\) molecule? (e) How many bonding pairs of electrons are in the \(\mathrm{PF}_{3}\) molecule?
See all solutions

Recommended explanations on Chemistry Textbooks

The Earths Atmosphere

Read Explanation

Physical Chemistry

Read Explanation

Organic Chemistry

Read Explanation

Inorganic Chemistry

Read Explanation

Chemistry Branches

Read Explanation

Ionic and Molecular Compounds

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free