Question

Complete the sentences to explain why the lattice energy of potassium bromide is more exothermic than the lattice energy of rubidium iodide?

Answer 1

Due to strong forces of attraction in potassium bromide, the lattice energy of potassium bromide is more exothermic than rubidium iodide.

Further Explanation:

Lattice energy:

It is the amount of energy released when ions are combined to form an ionic compound or the energy required to break the ionic compound into its constituent gaseous ions. It cannot be measured directly and is denoted by ${\mathbf{\Delta}}{{\mathbf{H}}_{{\mathbf{lattice}}}}$ . It can have positive as well as negative values.

Case I: Positive lattice energy

The value of lattice energy $({\text{\Delta }}{{\text{H}}_{{\text{lattice}}}})$ comes out to be positive if the energy supplied to the system is more than that released during the reaction. In other words, ${\mathbf{\Delta}}{{\mathbf{H}}_{{\mathbf{lattice}}}}$ is positive in case of endothermic reactions.

Case II: Negative lattice energy

The value of lattice energy $({\text{\Delta }}{{\text{H}}_{{\text{lattice}}}})$ comes out to be negative if the energy released by the system is more than the energy supplied during the reaction. In other words, ${\mathbf{\Delta}}{{\mathbf{H}}_{{\mathbf{lattice}}}}$  is negative in case of exothermic reactions.

Lattice energy is used to determine the stability of ionic compounds.

The lattice energy of an ionic solid depends upon the following factors:

(1) The charge on the ions.

(2) The size or the radius of the ions.

The charge on the ions is directly related to the lattice energy, and therefore the lattice energy increases with increases in the charge on the ion. The size of an ion is inversely proportional to the lattice energy. Therefore, when the size of an ion increases, the lattice energy decreases.

As we move down the group in the periodic table, the size of an atom increases and therefore the lattice energy decreases.

The charge on the potassium ion and rubidium ion are +1, and the charge on the bromide ion and iodide ion are -1. Therefore the charge present on the ions in potassium bromide and rubidium iodide is same.

Potassium has smaller size as compared to rubidium ion, and bromide ion has smaller size as compared to iodide ion. The size of an ion is inversely proportional to the lattice energy and therefore potassium bromide has higher lattice energy as compared to rubidium iodide.

Potassium bromide is more effectively packed and has strong force of attraction as compared to rubidium iodide. This is the reason that more energy is released in the case of potassium bromide as compared to rubidium iodide.

Learn more:

1. Identify the chemical equation of the first ionization energy of the lithium: brainly.com/question/5880605

2. Arrange the elements, according to their first ionization energy: brainly.com/question/1550767

Answer details:

Grade: Senior School

Subject: Chemistry

Chapter: S-block elements.

Keywords: Lattice energy, potassium bromide, rubidium iodide, crystal lattice, exothermic, endothermic, elements, s-block, periodic table and ionic size.

Answer 2

The lattice energy is the amount of energy released when the ions that make up a crystal lattice are brought together. Now, this energy is dependent on the charge concentration of these ions. Both potassium and rubidium form ions with a +1 charge, while bromine and iodine form ions with -1 charge. However, because potassium and bromine are smaller than rubidium and iodine respectively, the charge is more concentrated. Therefore, more energy is released when potassium and bromine are brought together.