Energetics Flashcards
What is an exothermic reaction?
Reaction which gives out energy in the form of heat usually shown by rising temperature of the surroundings.
What is an endothermic reaction?
A reaction that takes in energy from the surroundings in the form of heat, usually shown by fall in temperature of the surroundings
How can you find out
enthalpy change?
Using a calorimetry.
What does calorimetry do?
Allows you to measure the amount of energy transferred in a chemical reaction.
How do you measure the amount of energy transferred in dissolving displacement and neutralisation reactions?
1) take the temperature of reactants
2) mix them
3) measure the temperature of the solution at the end of the reaction.
In order to investigate the enthalpy change of dissolving, displacement or neutralisation reactions. What do you need to use?
Polystyrene cup.
How do you reduce the amount of energy lost to the surroundings in a enthalpy, change investigation?
Give the polystyrene cup more insulation by putting it in a beaker of cotton wool, and putting a lid on the cup to reduce energy loss by evaporation..
Name the biggest problem with energy measurements
Amount of energy loss to the surroundings.
How do you measure the amount of energy transferred when a fuel is burned?
Burn the fuel and use the flame to heat up some water. Use a copper container as copper conduct heat well.
What can you do to make the calorimetry combustion experiment as accurate as possible?
Reduce draughts by using a screen
What is the equation for calculating heat transferred.
Q = m x c x delta T
How do you calculate enthalpy change?
1) calculate heat energy transferred ( Q = m x c delta T)
2) work out number of moles of reactant ( n= m /Mr)
3) then calculate molar enthalpy change by using ( delta H = Q/n)
4) then divide by 1000 to turn answer into kJ/mol.
What is the equation for enthalpy change?
Delta H = Q/n
