3.1.4 Energetics Flashcards
How can overall enthalpy change be calculated ?
Energy to break bonds - energy to make bonds (Bonds broken- Bonds formed)
What is the enthalpy of formation ?
The enthalpy change when one mole of a substance is produced from its elements under standard conditions
What is enthalpy of combustion ?
The enthalpy change when one mole of a element is burnt completely in oxygen under standard conditions
How do you calculate energy change ?
q=mc(triangle)T
What is specific heat capacity ?
The energy required to raise 1g of a substance by 1K without a change of state
Why are energy change values found using calorimetry never completely accurate ?
As energy is easily lost though conduction or convection and inaccuracies in measuring temperatures
What is an endothermic reaction ?
Reactions that absorb energy from the surroundings
What is an exothermic reaction ?
Reactions that release energy to the surroundings
Is breaking bonds exothermic or endothermic and why ?
Breaking bonds is endothermic as energy is absorbed
Is bond forming exothermic or endothermic and why ?
Forming bonds is exothermic as energy is released
What does Hess’s law state ?
The enthalpy change for a reaction is independent of the route taken
