9 Enthalpy Flashcards
What is enthalpy?
Enthalpy is a measure of the heat energy in a chemical system.
What is a chemical system?
The chemical system refers to the atoms, molecules, or ions making up the chemicals.
How do we calculate enthalpy change?
Enthalpy of products-enthalpy of reactants
What describes an exothermic change?
Energy transfer from the system to the surroundings.
What describes an endothermic change?
Energy transfer from the surroundings to the system.
Is enthalpy change positive or negative in an exothermic reaction?
Enthalpy change is negative.
Is enthalpy change positive or negative in an endothermic reaction?
Enthalpy change is positive.
What is activation energy?
The minimum energy required for a reaction to take place.
Why do reactions with small activation energies take place quickly?
Reactions with small activation energies take place very rapidly because the energy needed to break bonds is readily available from the surroundings.
What are the standard conditions?
A standard physical value.
1) Standard pressure: 100kPa
2) Standard temperature: 298K
3) Standard concentration: 1moldm-3
4) Standard state: The physical state of a substance under standard conditions.
What is the standard enthalpy change of reaction?
The enthalpy change that accompanies a reaction in the molar quantities expressed in a chemical equation under standard conditions, all reactants and products being in their standard states.
What is the standard enthalpy change of formation?
The enthalpy change that takes place when one mole of a compound is formed from its constituent elements in their standard states under standard conditions.
What is the standard enthalpy change of combustion?
The enthalpy change that takes place when one mole of a substance reacts completely with oxygen under standard conditions all reactants and products being in their standard states.
What is the standard enthalpy change of neutralisation?
The enthalpy change that accompanies a reaction of an acid by a base to form one mole of H2O, under standard conditions with all reactants and products in their standard states.
What does specific heat capacity mean?
The energy required to raise the temperature of 1g of a substance by 1°C.
