Potassium and hydrogen react to form the ionic compound potassium hydride. (b) Use data in Figures 7.10 and 7.12 to determine the energy change in kJ/mol for the following two reactions: K1g2 + H1g2 ¡ K+1g2 + H-1g2 K1g2 + H1g2 ¡ K-1g2 + H+1g2

Key Concepts

Ionic Compounds

Ionic compounds are formed through the transfer of electrons from one atom to another, resulting in the formation of charged ions. In the case of potassium hydride (KH), potassium (K) donates an electron to hydrogen (H), creating K+ and H- ions. Understanding the nature of ionic bonds is crucial for analyzing the energy changes during the formation and dissociation of such compounds.

Energy Change in Reactions

The energy change in a chemical reaction, often expressed in kJ/mol, indicates the difference in energy between reactants and products. This can be calculated using Hess's law or by analyzing bond energies. In the given reactions, determining the energy change involves understanding how the formation of ionic bonds releases energy, while breaking them requires energy input.

Standard State and Thermodynamic Data

Thermodynamic data, such as enthalpy changes, are typically reported under standard conditions (1 atm pressure and 25°C). Figures 7.10 and 7.12 likely provide necessary thermodynamic values for the reactants and products involved in the reactions. Familiarity with how to interpret and apply this data is essential for calculating the energy changes associated with the reactions of potassium and hydrogen.