Thermochemistry, Hess's Law And Bind Enthalpies Flashcards
What is the standard state
Most stable state of the substance under standard conditions one atmosphere and a specified temp usually 25degrees
What. Is the standard enthalpy
Refers to the enthalpy change for a reaction in which the reactants and products are in their standard states at a specific temps
What is the standard enthalpy of combustion of a substance
Energy given out when one mole of a substance completely burns in ixygen
What as the stands enthalpy of formation of a compound
Energy give out or taken in when one mole of comp formed from its elements in their standard states
What are standard enthalpy changes measured in
KJ/mol of reactant or products
The enthalpy change for a reaction
^H = €^Hprod- €^Hreact
What is delta H in endothermic reactions
Positive and the enthalpy of the product is greater than reactants
The delta H for an exothermic reaction
Negative and the reactants are greater than products
What is calorimetry
The quantative determination of the change of heat energy which occurs during a chemical reaction
What is Hess’s law
The enthalpy change of reaction depends only on the enthalpies of the starting reactants and of the final products but it’s independent of what route is taken
What is the first law of thermodynamics
Entry can neither be destroyed or created
When working our bind enthalpies
Write out the chemical equation and work out the bond breaking and bond making at either side then put them all together to get the overall enthalpy change
Helps to write structural of compounds/elements to see how
Is the delta H for bond breaking/making positive or negative
Bond breaking positive
Bond making negative
