Siklus Born-Haber, Energi Kisi, Hukum Hess Part 1 Kimia 11 SMA Kmerdeka

Summary

This video from Klinik Bimbel discusses the Born-Haber cycle, focusing on lattice energy and its role in ionic bonding. The presenter explains how lattice energy is released when ions form a crystal, with factors such as ion charge and radius affecting its magnitude. Using examples like CaF2 and NaF, the video demonstrates the Hess Law and its application to lattice energy calculations. Additionally, a detailed breakdown of the Born-Haber cycle for NaCl formation is provided, alongside exercises to practice Hess's Law and energy concepts.

Takeaways

• 🔍 The Born-Haber cycle explains ionic bonding and energy, focusing on lattice energy.
• ⚡ Lattice energy refers to the energy released when gas-phase ions combine to form an ionic crystal.
• 📈 Lattice energy is proportional to the charge of the ions and inversely proportional to the distance between them.
• 🔄 Larger ion charges result in higher lattice energy, as seen in CaF2 compared to NaF.
• 🔬 Lattice energy decreases with increasing ionic radius, as shown by comparing MgF2 (smaller ions) to CaF2.
• 🔑 In the periodic table, atomic radius increases down a group, which affects the distance between ions and lattice energy.
• 🧪 The Born-Haber cycle uses Hess's Law to calculate lattice energy by summing different steps such as sublimation, ionization, and electron affinity.
• 🔧 The formation of NaCl from Na+ and Cl- is used as an example to illustrate the application of the Born-Haber cycle.
• 🧮 Hess's Law helps calculate enthalpy changes by adding reactions and adjusting for coefficients.
• 📊 In examples involving graphite and diamond, reversing or modifying reactions as needed alters enthalpy calculations, reflecting Hess's Law principles.

Q & A

What is the Born-Haber cycle?

The Born-Haber cycle is a thermochemical process used to analyze the formation of ionic compounds. It involves calculating the lattice energy, which is the energy released when gaseous ions combine to form a crystalline ionic solid.

What is lattice energy and what does it depend on?

Lattice energy is the energy released when ions in the gas phase combine to form an ionic crystal. It depends on the charges of the ions and the distance between them. Higher ion charges and smaller distances lead to greater lattice energy.

Why does CaF2 have a greater lattice energy than NaF?

CaF2 has a greater lattice energy than NaF because the calcium ion (Ca2+) has a +2 charge, while the sodium ion (Na+) has only a +1 charge. The larger charge on Ca2+ increases the electrostatic attraction, leading to a higher lattice energy.

How does ion size affect lattice energy?

Lattice energy is inversely proportional to the distance between ions. Smaller ions are closer together, so compounds with smaller ions have higher lattice energy. For example, MgF2 has a higher lattice energy than CaF2 because the Mg2+ ion is smaller than the Ca2+ ion.

What is Hess’s law and how is it used in the Born-Haber cycle?

Hess's law states that the total enthalpy change of a reaction is the same regardless of the steps taken. In the Born-Haber cycle, it is used to calculate lattice energy by adding up all the enthalpy changes involved in forming an ionic compound.

What are the key steps in the Born-Haber cycle for forming NaCl?

The key steps include: sublimation of solid Na, ionization of gaseous Na to form Na+, dissociation of Cl2 into Cl atoms, electron affinity of Cl to form Cl-, and finally the combination of Na+ and Cl- to form NaCl with the release of lattice energy.

What is electron affinity and how does it relate to the Born-Haber cycle?

Electron affinity is the energy released when an atom gains an electron to form a negative ion. In the Born-Haber cycle, the electron affinity of chlorine is involved when a chlorine atom gains an electron to form Cl-.

Why is it necessary to balance the reaction equations in the Born-Haber cycle?

Balancing the reaction equations ensures that the number of atoms and charges on both sides of the reaction are equal. This is important for accurately calculating the enthalpy changes and lattice energy in the Born-Haber cycle.

How is the lattice energy (U) related to other enthalpy changes in the Born-Haber cycle?

The lattice energy (U) is one of the terms in Hess's law equation. It is related to the sublimation energy, ionization energy, bond dissociation energy, and electron affinity. All these values add up to the total enthalpy change of the formation of the ionic compound.

How is the enthalpy of formation (ΔHf) related to the Born-Haber cycle?

The enthalpy of formation (ΔHf) is the total change in enthalpy when an ionic compound is formed from its constituent elements. It is a key part of the Born-Haber cycle, and all the other enthalpy changes, including lattice energy, sum up to equal ΔHf.