Term 4

Question 1

Enthalpy changes def

Answer 1

• change in a reaction at constant pressure

Question 2

Endothermic reaction def

Answer 2

• reaction that absorbs energy from surroundings

• product higher energy than reactants - positive entgalpy change

Question 3

Exothermic reaction def

Answer 3

• reactions that release energy to surroundings

• products lower in energy than reactants
• enthalpy change is negatuve

Question 4

4types of enthalpy changes

Answer 4

• standard enthalpy change of reaction
• standard enthalpy change of neutralisation

• standard enthalpy change of combustion

•standard enthalpy change of formation

Question 5

Standard enthalpy change of reaction def ( triangle with r symbol)

Answer 5

• the enthalpy change of a reaction according to molar quantities in equation under standard conditions

Question 6

Standard enthalpy change of neutralisation ( triangle w neut)

Answer 6

• the enthalpy change when an acid and alkali react to form 1 mole of water under standard conditions

Question 7

Standard enthalpy change of combustion ( triangle w c)

Answer 7

• enthalpy change when one mole of a substance is completely burned in oxygen to make co2 and h20 under standard conditions

Question 8

Standard enthalpy change of formation (triangle f)

Answer 8

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

Question 9

Bonds broken=

Answer 9

Energy needs to be as dined
- endothermic so enthalpy change is pos

Question 10

Bonds made=

Answer 10

• energy is released
• bonds r made when products r being procured
• exothermic process - negative enthalpy change