FC19 Enthalpy Flashcards
In an exothermic reaction, is the enthalpy change positive or negative
Negative
Why in an exothermic reaction is the enthalpy change negative
The reaction produces a lower energy state, the energy is released as heat, so the temperature rises
In an endothermic reaction is the enthalpy change positive or negative
Positive
When drawing enthalpy profile diagrams, what must you always remember to write on the graph
The names of the reactants and the products
When drawing enthalpy profile diagrams, what arrow must only have one direction
The enthalpy change, ensuring it’s facing the correct direction
What are the 2 standard conditions
- 1 atmosphere
- 25 degrees C
Define the enthalpy change of reaction
The enthalpy change for a reaction in the molar quantities shown in a chemical equation, under standard conditions
Define enthalpy change of formation
The enthalpy change for the formation of 1 mole of a compound formed from it’s elements in their standard states under standard conditions
Define enthalpy change of combustion
The enthalpy change for the complete combustion of 1 mole of a substance, under standard conditions
Define enthalpy change of neutralisation
The enthalpy change for the formation of 1 mole of water from the neutralisation of an acid by a base, under standard conditions
What is the equation for determining enthalpy change
q=mc(change in temp)
m- mass of substance heated or cooled
c- specific heat capacity
q- usually given J
List a few examples of exothermic reactions
- Condensation
- Combustion
- Base neutralising acid
List a few examples of endothermic reactions
- Vaporisation
- Decomposition
Is bonds breaking endo or exo
Endothermic
Is bonds making endo or exo
Exothermic
