Electro-chemistry - QS Study
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Electron Gain or Electron Affinity

Definition: The electron gain (or electron affinity) (ΔH0eg) is the energy change when one electron is added to each atom to form a negative ion.......

Bond Dissociation Enthalpy

Sometimes the value for the bond dissociation enthalpy is instead given. Note that this bond dissociation enthalpy refers to one bond, so is double the......

Standard Enthalpy of Formation

Standard enthalpy of formation (ΔH0f) Definition: One mole of the compound is formed from its elements in their standard states. For example, sodium chloride (NaCl)......

Describe on Born-Haber Cycle

Lattice enthalpies cannot be determined directly but an application of Hess’s law to the formation of an ionic crystal called the ‘Born-Haber cycle’ can be......

Describe on Lattice Enthalpy

The strength of the covalent bonds can be measured by the bond enthalpy. In ionic compounds the comparable enthalpy value which relates to the strength......

Calculating the Enthalpy Change of a Reaction

The simplest way to apply Hess’s Law is to remember that the enthalpy change of any reaction is equal to the total formation energy of......

Hess’s Law

How can the enthalpy ΔH be discovered if the enthalpy changes for reactions are too difficult or impossible to determine experimentally? If for example, the......

Thermo-chemical Equations

A thermo-chemical equation is the chemical equation for a reaction in which the enthalpy of reaction for the molar amounts stated is written directly after......

Measuring pH Solution

The pH of a solution can accurately be measured using a pH meter. Although less precise, acid-base indicators are often used to measure pH because......

pOH Measurement

A measurement of the hydroxide ion concentration, similar to pH, is called pOH. The pOH of a solution is defined as the negative logarithm of......

Solutions of pH

Although one can quantitatively describe the acidity of a solution by its concentration [H+], it is more convenient to determine the acidity in terms of......

Acidic Basic

In an acidic solution, the concentration of H+ (aq) is greater than that of OH+ (aq). After dissolving substances in water, one can alter the concentrations......

Solutions of Strong Acid or Base

We know that in a solution of a strong acid one can normally ignore the self-ionisation of water as a source of a few extra......

Ionic Product Constant of Water

H2O and Kc are both constant and combining these constants together make up the ionic product constant for water, written KW. KW = [H3O+] [OH-]......

Self-ionisation of Water

For a strong acid, the concentration of the ions will equal the concentration of the acid. e.g. 0.1 M HC1 (aq), [H+] = 0.1 M......