Standard enthalpy change Flashcards
What are standard conditions?
298K
100kPa
Define standard enthalpy change of formation
The enthaply change when 1 mol of a substance is formed from its constituent elements under standard conditions, with all substances in their standard states.
What is a combustion reaction?
A combustion reaction is when a substance reacts with oxygen to release heat energy.
In a combustion reaction, a substance where carbon is a constituent element reacts to form…
carbon dioxide
In a combustion reaction, a substance where hydrogen is a constituent element reacts to form…
water
In a combustion reaction, a substance where a metal is a constituent element reacts to form…
a metal oxide
What product is formed in complete combustion of a substance containing carbon?
CO2
What products are formed in incomplete combustion of a substance containing carbon?
CO or C
Define the standard enthalpy change of combustion
The standard enthalpy of combustion is the enthalpy change when one mole of a substance is completely burnt in oxygen under standard conditions, with all reactants and products in their standard states
If an element is in its standard state and under standard conditions, then its enthalpy of formation is…
0kJmol-1
If the initial and final conditions of a reaction are the same…
The total enthalpy change along the direct route will be equal the total enthalpy change along the alternative route.
Define Hess’ law
The enthalpy change in a reaction at constant pressure is independent of the route taken
