A2 energetics Flashcards
what does ΔH mean?
enthalpy change
for example:
ΔH = ± 1790 kJ mol-1
what does Ea mean?
activation energy
what are the two equations used in calorimetry?
Q=mcΔT
where c is the specific heat capacity of 4.18.
ΔH = -Q/moles
where Q has been converted to kJ.
what is the standard condition of temperature?
298 K
what is the standard condition of pressure?
100 kPa
what is the standard condition of concentration?
1mol dm-3
what is the definition of the standard enthalpy change of the reaction?
…a reaction in the molar qualities specified in the chemical equation…
what is the definition of the standard enthalpy change of formation?
…one mole of a compound is formed from its elements…
what is the definition of the standard enthalpy change of combustion?
…one mole of a substance reacts completely with oxygen…
what is the definition of the standard enthalpy change of neutralisation?
…the reaction of an acid and a base to form one mole of liquid water…
what is the definition of both enthalpy?
the energy required to break one mole of a specific type if bond in a gaseous molecule.
what are the two limitations to both enthalpy?
1) not everything is a gas.
2) bond enthalpies are averages.
what are the sources of error in calorimetry which make ΔH less negative?
- heat being lost to surroundings
- incomplete combustion.
- evaporation of fuel.
what is the affect of using tap water instead of distilled water in calorimetry?
c (specific heat capacity) will be different, so hard to say.
what affect does the evaporation of water in calorimetry have?
make mass and ΔT different, therefore hard to say.
why is water being produced as a gas and not as a liquid in calorimetry a problem?
not under standard conditions.
