Enthalpy Level Diagrams Flashcards
what is an enthalpy level diagram
- a graph showing enthalpy, H, over nothing on the x axis
- it just shows how the energy change that occurs
what would the enthalpy level diagram of an exothermic reaction look like
- the line would be horizontal
- then drop to a lower level
- and then continue to be horizontal
what would the enthalpy level diagram of an endothermic reaction look like
- the line would be horizontal
- then rise to a higher level
- an then continue to be horizontal
what wold the drop an rise in the enthalpy level for both diagrams be denoted by
- an arrow showing the direction of the enthalpy change
- with delta H being next to it showing that that is what is increasing or decreasing
what would horizontal lines before and after be
- the horizontal line before would represent the enthalpy of the reactants
- which the second horizontal line would represent the enthalpy of the products
what is the formula for calculating the enthalpy change from an enthalpy level diagram
delta H = H of products - H of reactants
why must the subtraction be in that order
- because you need to know whether the enthalpy change has a positive or negative value
- in order to know whether the reaction is exo or endothermic
- as for an exothermic reaction where the enthalpy of the products is less than the reactants, doing a subtraction of a lower number from a higher one would give you a negative number
- correctly indicating en exo reaction and loss of heat energy
what else should you place in enthalpy level diagrams that you didnt need to in GCSEs
- the names of the reactant and products on their respective horizontal lines
- as well as their state symbols
- the values for delta H should be written next to the arrow if you know it
what wouldnt you show on an enthalpy level diagram that you would in an enthalpy profile diagram
- the labeling of the x axis
- and the activation energy of the reaction
