151Guo11Blch5Part3 - 9/29/2009 Hesss Law Hesss Law H is...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
9/29/2009 1 Hess’s Law ± H is well known for many reactions, and it is inconvenient to measure H for every reaction in which we are Thermochemistry interested. • However, we can estimate H using H values that are published and the properties of enthalpy. Hess’s Law Hess’s law states that “If a reaction is carried out in a series of Thermochemistry steps, H for the overall reaction will be equal to the sum of the enthalpy changes for the individual steps.” Hess’s Law Because H is a state function, the total enthalpy change Thermochemistry enthalpy change depends only on the initial state of the reactants and the final state of the products. Enthalpies of Formation An enthalpy of formation, H f , is defined as the enthalpy change for the reaction in which a compound is made from its Thermochemistry constituent elements in their elemental forms. Standard Enthalpies of Formation Standard enthalpies of formation, H f , are measured under standard conditions (25 °
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 3

151Guo11Blch5Part3 - 9/29/2009 Hesss Law Hesss Law H is...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online