Bond enthalpy Flashcards
What is bond enthalpy?
The energy required to break a bond
Is bond making exothermic or endothermic?
Exothermic - energy is released
Does bond formation have a positive or negative energy change?
Negative
Is bond breaking exothermic or endothermic?
Endothermic - energy is absorbed
Does bond breaking have a positive or negative energy change?
Positive
What is mean bond enthalpy?
Average energy needed to break a certain type of bond, over a range of compounds
How do you calculate the enthalpy change of reaction?
Total energy absorbed - energy released
Break - make
Whats a good way to remember which of break or make is endothermic or exothermic?
Bendo Mexo
Break - endo-thermic
Make - exo-thermic
Why are mean bond enthalpies inaccurate?
- They are only valid in the gas phase
- They depend on the particular molecule
- Generally quoted so can only be used as a guide
What is the definition of the standard enthalpy change of formation?
The enthalpy change when 1 mole of a compound is formed from 1 mole of its elements with both products and reactants in their standard states, under standard conditions
What is the definition of the standard enthalpy change of combustion?
The enthalpy change when 1 mole of a substance is completely burned in oxygen with all reactants and products in their standard states under standard conditions
What is the standard enthalpy of reaction?
The enthalpy change when a reaction occurs in molar quantities shown in the chemical equations, under standard conditions with all products in their standard states
