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Flashcards in Bond enthalpy Deck (12)
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1
Q

What is bond enthalpy?

A

The energy required to break a bond

2
Q

Is bond making exothermic or endothermic?

A

Exothermic - energy is released

3
Q

Does bond formation have a positive or negative energy change?

A

Negative

4
Q

Is bond breaking exothermic or endothermic?

A

Endothermic - energy is absorbed

5
Q

Does bond breaking have a positive or negative energy change?

A

Positive

6
Q

What is mean bond enthalpy?

A

Average energy needed to break a certain type of bond, over a range of compounds

7
Q

How do you calculate the enthalpy change of reaction?

A

Total energy absorbed - energy released

Break - make

8
Q

Whats a good way to remember which of break or make is endothermic or exothermic?

A

Bendo Mexo
Break - endo-thermic
Make - exo-thermic

9
Q

Why are mean bond enthalpies inaccurate?

A
  • They are only valid in the gas phase
  • They depend on the particular molecule
  • Generally quoted so can only be used as a guide
10
Q

What is the definition of the standard enthalpy change of formation?

A

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

11
Q

What is the definition of the standard enthalpy change of combustion?

A

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

12
Q

What is the standard enthalpy of reaction?

A

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