9.1 Enthalpy changes Flashcards
What is Enthalpy?
Enthalpy, H is the measure of heat in a chemical system
What is the equation for enthalpy change?
H(products) - H(reactants)
What is the Law of conservation of energy?
Energy cannot be created or destroyed
What does it mean if the enthalpy change is exothermic?
Energy is transferred from the system to the surroundings.
The enthalpy change will be negative.
The temperature of the surroundings increases
What does it mean if the enthalpy change is endothermic?
Energy is transferred from the surroundings to the system.
The enthalpy change is positive.
The temperature of the surroundings decreases.
What is activation energy?
The minimum amount of energy required to start a reaction
What is standard pressure?
100kPa
What is standard temperature?
298K
What is standard concentration?
1 mol dm-3
What is standard state?
Standard state is the physical state of a substance under standard conditions.
What is standard enthalpy change of formation?
The enthalpy change that takes place when one mole of a compound is formed from its elements under standard conditions with all the reactants and products in their standard states.
What is standard enthalpy change of combustion?
The enthalpy change that takes place when one mole of a substance reacts completely with oxygen under standard conditions, with all the reactants and products in their standard states.
What is standard enthalpy change of neutralisation?
The energy change that accompanies the reaction of an acid by a base to form one mole of water under standard conditions, with all the reactants and products in their standard states.
