enthalpy change Flashcards
What is 1st ionisation energy?
**The enthalpy change that occurs when one mole of electrons is removed from one mole of gaseous atoms to form one mole of gaseous 1+ ions.
What is 2nd ionisation energy?
The enthalpy change that occurs when one mole of electrons is removed from one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions.
What is standard enthalpy change of formation?
The enthalpy change that occurs when one mole of a compound is formed from its elements under standard conditions (100kPa, 298K) with all reactants and products in their standard states.
What is the standard enthalpy change of combustion?
The enthalpy change that occurs when one mole of a compound completely reacts/burns with oxygen under standard conditions (100kPa, 298K) where all reactants and products in their standard states.
What is the standard enthalpy of neutralisation?
The enthalpy change that occurs when an acid reacts with a base to form one mole of water (liquid) under standard conditions (100kPa, 298K) with all reactants and products in their standard states.
Reasons that would lead to a less exothermic value of enthalpy change of combustion than expected.
- Heat loss to surroundings other than water, e.g. beaker.
- Incomplete combustion
- Evaporation of reaction from the wick
- Non-standard conditions
What is Hess’ Law?
Hess’ Law states that if a reaction can take place by two routes, and the starting and finishing conditions are the same, the total enthalpy change is the same for each route.
What is the standard enthalpy change of a reaction?
The standard enthalpy change of a reaction is the enthalpy change of a reaction under standard conditions (100kPa, 298K) with all reactants and products in their standard states.
What is an exothermic reaction?
In an exothermic reaction, more energy is released when product bonds are formed than is needed to break reactant bonds. Overall, the reactions releases energy.
How do you work out enthalpy change?
(Sum of bond enthalpies of reactants) - (Sum of bond enthalpies of products)
What is an endothermic reaction?
In an endothermic reaction, more energy is needed to break the reactant bonds than is released when the product bonds are formed. Overall, the reaction takes in energy.
What is average bond enthalpy?
The average amount of energy needed to break a type of bond homolytically in gaseous molecules.
What is activation energy?
The minimum amount of energy required for a reaction to begin by breaking the bonds in the reactants.
What is 1st electron affinity?
The enthalpy change that occurs when one mole of electrons is added to one mole of atoms to form one mole of gaseous 1- ions.
What is 2nd electron affinity?
The enthalpy change that occurs when one mole of electrons is added to one mole of gaseous 1- ions to form one mole of gaseous 2- ions.
What is lattice enthalpy?
The enthalpy change that occurs when one mole of an ionic compound is formed from its gaseous ions under standard conditions (100kPa, 298K).
What is standard enthalpy change of atomisation?
The enthalpy change that occurs when one mole of gaseous atoms is formed from its elements in its standard state under standard conditions (100kPa, 298K).
Is 1st ionisation energy endothermic or exothermic?
1st ionisation is endothermic because more energy has to be put in to overcome the electrostatic force of attraction between the negatively charged electron and the positively charged nucleus.
Is 2nd ionisation energy endothermic or exothermic?
2nd ionisation energy is more endothermic than the first because more energy has to be put in to overcome the electrostatic force of attraction between the negatively charged electron and the positively charged ion.
Is 1st electron affinity endothermic or exothermic?
1st electron affinity is exothermic as the electron that is being added on is attracted to the positively charged nucleus/
Is 2nd electron affinity endothermic or exothermic?
2nd electron affinity is endothermic as more energy has to be put in to overcome the repulsion between the electron being added on and the negatively charged ion.
Is lattice enthalpy endothermic or exothermic?
Lattice enthalpy is exothermic because strong ionic bonds are formed due to the electrostatic force of attraction between the oppositely charged ions.
Is enthalpy change of atomisation endothermic or exothermic?
Enthalpy change of atomisation is endothermic as energy has to be put in to break the bonds to form atoms.
Standard Enthalpy change of hydration
Enthalpy change when 1 mole of gaseous ions dissolve in water to form 1 mole of aqueous ions under standard conditions.
