Topic 5 Flashcards
What is heat?
Form of energy that can be transferred from a higher to lower temperature object
What is temperature?
Average Ek of particles in a substance
What is enthalpy?
The heat absorbed or released in a chemical reaction at constant pressure
Can enthalpy be measured?
No only enthalpy change
What is standard enthalpy change?
The enthalpy change of a reaction carried out under standard conditions with everything in its standard state ( 100 kPA, 298 k)
Features of a exothermic reaction
- Energy is released to the surrondings
- Temp of the surrondings increases
- Combustion and nuetralisation
Draw an enthalpy diagram for exothermic reaction
Features of an endothermic diagram
- temperature of surrondings decrease
- energy is taken in
- thermal decomposition and photosynthesis
What is the equation for energy
q=mc delta t
What is the equation for enthalpy change?
Delta H = q/n
Assumptions of calorimetry
- Assume there is no heatloss to the surrondings and the calorimeter
- Assume that the SHC is the same as water
- Assume that the combustion is complete
What is standard enthalpy change of formation
When one mole of a compound is formed from its constituent elements in their standard states with everything under standard conditions
What is the formula for enthalpy change?
Enthalpy change = sum of standard enthalpy change of formation of products - sum of standard enthalpy change of reactants
What is standard enthalpy change of combustion?
The enthalpy change when one mole of a substance is completely burned in oxygen under standard conditions
Draw a basic enthalpy cycle diagram