Energetics Flashcards
What is an exothermic reaction
A reaction that gives out energy usually in the form of heat
How would an exothermic reaction usually show itself
A rise in temperature in the surroundings
What is an endothermic reaction
A reaction that takes in energy from the surroundings usually in the form of heat
How would an endothermic reaction usually show itself
A fall in temperature in the surrounding
What is the overall change in energy in a reaction known as?
Enthalpy Change (kJ/mol)
What happens to the enthalpy change when the reaction is eXothermic
The result is negative
If an enthalpy change has a positive value what kind of reaction is it?
Endothermic (taking in energy)
What are reaction profiles / energy level diagrams
Shows the energies of the reactants and the products and how the energy changes over the course of the reaction
How would you label the axis in a energy level diagram
X - Progress of reaction Y - Energy
What is calorimetry
Allows you to measure how much energy is transferred in a chemical reaction
How do you measure dissolving and displacement reactions?
Take the temperature of the reactants, making sure they’re the same
Mix them in a polysteryene cup
Try to reduce the amount of energy lost to the surroundings by putting a lid on it
Measure the solution at the end of the reaction
How do you measure the energy transferred in a neutralisation reaction?
Put the same amount of each reactant into separate beakers
Place them in a water bath until they’re the same temperature
Add both reactants to a polystyrene cup with a lid
Take the temperature every 30 seconds and record the highest temperature
How do you measure the energy transferred in a combustion reaction
Record the water temperature
Weight the spirit burner and the lid
Heat the water in a copper container using the spirit burner, making sure you reduce the draughts with a screen
Stir it until the temperature is around 50 degrees celsius
Measure the temperature of the water
Weight the spirit burner and the lid again
How do you calculate the heat energy transferred
Q = m x c x ΔT
How do you work out the molar enthalpy change
Calculate heat tranferred (Q = m x c x ΔT)
Work out change in mass of the spirit burner
Work out how much 1g of fuel produces in terms of energy (kJ)
Work out number of moles (mass(g)/RFM)
Work out enthalpy change (energy transferred/num moles)
