Types of enthalpy changes

Question 1

Standard enthalpy of combustion

Answer 1

• energy released
• 1 mol of substance
• completely burnt in excess oxygen
• 298K and 1 atm /100 kPa

Question 2

Standard enthalpy change of neutralization

Answer 2

• energy released
• 1 mol of water
• formed from reaction of acid and base
• 298K, 1 atm/100kPa

Question 3

Standard enthalpy change of formation

Answer 3

• energy change
• 1 mol of substance (product)
• formed from its elements in normal physical state
• 298K, 100kPa, 1 atm (standard conditions)
• more exo, more stable

Question 4

Average bond enthalpy/energy

Answer 4

• average energy absorbed
• 1 mole of X-Y bonds
• broken in (g) state to form X and Y (g) atoms
• average from other values from similar compounds
• 298K, 100kPa, 1 atm