Enthalpy Flashcards
Is bond breaking exothermic or endothermic?
Endothermic
Is bond making exothermic or endothermic?
Exothermic
What does exothermic mean?
More energy is being released than there is going into the reaction
What does endothermic mean?
More energy goes into the reaction than there is going out of the reaction
What is the enthalpy change of heat in an endothermic reaction?
Positive
What is the enthalpy change of heat in an exothermic reaction?
Negative
What is the enthalpy change of heat?
The overall energy change in a reaction
What is the enthalpy change of formation?
The energy change when 1 mole of a substance is made from its constituent element in their standard state
What is the standard state for temperature?
25 degrees celsius / 298K
What is the standard state for pressure?
1 atm / 100KPa
What is the standard state for a solution?
1 mol/dm3
What is the standard state for moles?
1 mol
What is the equation for the enthalpy change of reaction in a formation reaction?
Enthalpy of a reaction = sum of products - sum of reactants
What happens if the element is on its own in an enthalpy of formation reaction?
It is 0
What is the enthalpy change of combustion?
The energy change when 1 mole of a substance is completely combusted at RTP
What is the equation for the enthalpy change of reaction in a combustion reaction?
Enthalpy of a reaction = sum of reactants - sum of products
What is Hess’s law?
When you use a mixture of combustion and formation enthalpies to find the overall enthalpy of an equation
What is specific heat capacity?
The energy needed to heat up 1 kg of a substance by 1 degree
What is a system?
The chemical reaction in the atoms and bonds
Is the line for reactants higher or lower than the products in an enthalpy reaction that is exothermic?
Lower
Is the line for reactants higher or lower than the products in an enthalpy reaction that is endothermic?
Higher
What is activation energy?
The minimun energy required to start a reaction
What is the enthalpy change of a reaction?
The energy change associated with any given reaction
What is the enthalpy change of combustion?
The enthalpy change where 1 mol of water is produced by neutralisation at STP