Hess’s law allows measuring the enthalpy change (ΔH) for a reaction without making calorimetric measurements. To do this, we need the enthalpies of some other reactions. For example, Using the given data for reactions (1) and (2), calculate the ΔH for … Read more
Standard enthalpy of formation (or heat of formation), ΔHof , is the enthalpy change when 1 mol of the substance is formed from its constituent elements in their standard states. For example, the formation of 1 mol ammonia from H2 … Read more
The enthalpy change for a chemical reaction (ΔHrxn), also known as the enthalpy of reaction or heat of reaction is often given next to the chemical equation. These are called thermochemical equations. For example, the enthalpy change for the combustion … Read more
Different objects require a different amount of heat to increase their temperature. For example, if you heat a beaker with 100 g of water and a 100-g iron plate, the latter will reach a high temperature a lot faster than … Read more
The first law of thermodynamics is the law of energy conservation, which states that energy can be converted from one form to another, but cannot be created or destroyed. One implication of this law is that the total energy of … Read more
