Chapter 2 - Developing Fuels Flashcards
Endothermic reaction
- energy is taken from the surroundings
- surroundings get colder
- ends up with a positive enthalpy change
Exothermic reaction
- energy is given out to the surroundings
- the surroundings get hotter
- the enthalpy change is negative
Standard conditions
Set conditions to allow us to compare enthalpy changes
- 298K (Kelvin) (25°c)
- pressure of 1atm (100KPa)
- when solutions are involved, a concentration of 1moldm-1
- 🔺Hø -this symbol represents standard conditions
Standard enthalpy change for a reaction (🔺rHø298)
The enthalpy change when molar quantities of reactants as stated in the equation react together under standard conditions
Standard enthalpy change of combustion (🔺cHø298)
The enthalpy change that occurs when one mole of a substance is burnt completely in oxygen under standard conditions in standard states
Standard enthalpy change of formation (🔺fHø298)
The enthalpy change when one mole of a compound is formed from its elements under standard conditions in standard states
Standard enthalpy change of neutralisation (🔺neutHø298)
The enthalpy change when one mole of hydrogen ions react with one mole of hydroxide ions to form one mole of water under standard conditions and in solutions containing 1moldm-3
Standard states
The physical state of a substance under standard conditions. This may be a pure soli, liquid or gas