Topic 8 - Energetics I Flashcards
Define enthalpy
A thermodynamic quantity equivalent to the total heat content of a system
Define standard enthalpy change of reaction
The enthalpy change measured at 100kPa and 298K when the number of moles of the substances in the equation as written react
Define standard enthalpy change of formation
The enthalpy change measured at 100kPa and 298K when one mole of a substance is formed from its elements in their standard states
Define standard enthalpy change of combustion
The enthalpy change measured at 100kPa and 298K when one mole of a substance is completely burned in oxygen
Define standard enthalpy change of neutralisation
The enthalpy change measured at 100kPa and 298K when one mole of water is produced by the neutralisation of an acid with an alkali
Give the equation for energy transferred, Q
Q=mcΔT
Define bond enthalpy
The enthalpy change when one mole of a bond in the gaseous state is broken
Define mean bond enthalpy
The enthalpy change when one mole of a bond, averaged out over many different molecules, is broken
In what type of reaction do the products have more energy than the reactants?
Endothermic
Given the molar mass in gmol-1 and the energy required in kJg-1, how could you calculate the energy required in kJmol-1?
Multiply the molar mass and the energy required in kJg-1
How do you calculate the enthalpy of formation of a product?
Enthalpy of combustion of reactants - Enthalpy of combustion of products
How do you calculate the enthalpy of reaction using mean bond enthalpies?
Sum of bonds broken - Sum of bonds formed
What are the limitations of using mean bond enthalpies to calculate the enthalpy of reaction?
It does not take state into account if the compounds present are anything other than gaseous
