Chapter 2 - Developing Fuels

Question 1

Endothermic reaction

Answer 1

• energy is taken from the surroundings
• surroundings get colder
• ends up with a positive enthalpy change

Question 2

Exothermic reaction

Answer 2

• energy is given out to the surroundings
• the surroundings get hotter
• the enthalpy change is negative

Question 3

Standard conditions

Answer 3

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

Question 4

Standard enthalpy change for a reaction (🔺rHø298)

Answer 4

The enthalpy change when molar quantities of reactants as stated in the equation react together under standard conditions

Question 5

Standard enthalpy change of combustion (🔺cHø298)

Answer 5

The enthalpy change that occurs when one mole of a substance is burnt completely in oxygen under standard conditions in standard states

Question 6

Standard enthalpy change of formation (🔺fHø298)

Answer 6

The enthalpy change when one mole of a compound is formed from its elements under standard conditions in standard states

Question 7

Standard enthalpy change of neutralisation (🔺neutHø298)

Answer 7

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

Question 8

Standard states

Answer 8

The physical state of a substance under standard conditions. This may be a pure soli, liquid or gas