Teach AP® chemistry with confidence and ease Open, Closed & Isolated Systems A system refers to any parts of the universe being studied. If you are conducting an experiment in a beaker, then the system you are studying is in Read More …
Propane Combustion When 0.5 g of propane is burned, the heat produced is used to raise the temperature of 100 cm³ of water from 20ºC to 40ºC. Calculate the enthalpy change (ΔH) for the reaction. Given the density of water Read More …
Enthalpy Entropy Gibbs Free Energy Enthalpy is the amount of heat energy transferred (heat absorbed or emitted) in a chemical process under constant pressure. Entropy measures the amount of heat dispersed or transferred during a chemical process. Gibbs Read More …
The term enthalpy change is a term to describe the amount of heat that passes in or out of a system during a chemical reaction under constant pressure. Calorimeter In school, you can measure the heat exchange of a reaction Read More …
(Picture above – dog escaping over the fence – winter 2015) A spontaneous process A spontaneous process is a physical or chemical change that occurs with no outside intervention. In life, many things happen spontaneously. For example, my dog escaped Read More …
Hess’s law states that energy change in the overall chemical reaction is the sum of energy change or enthalpy change in the individual reactions that comprises it. Hess’s Law states that the heat evolved or absorbed in a chemical process is Read More …
Methane gas – CH₄ What is the enthalpy change when methane is formed using carbon graphite and hydrogen? When a chemical reaction takes place, heat is either given off or absorbed. If heat is given off, it is called an Read More …
What is Gibbs Free Energy? For a simple definition, Gibbs free energy can be described as the amount of energy available to do work. Gibbs Free Energy is invented by Josiah Willard Gibbs (February 11, 1839 – April 28, 1903) Read More …
The Haber process to manufacture ammonia using nitrogen and hydrogen is given by the equation below: Calculate Gibb’s free energy change (ΔG) at 298 K temperature. Given the entropy change (ΔS): -198 J K⁻¹ mol⁻¹ Enthalpy change (ΔH): -92 kJ Read More …
What is entropy? Entropy refers to the amount of unusable energy in a system. When water flows over a dam, it loses some of its useful energy as heat Solid wood burns to become ash and releases gases. Solid ice Read More …
