Topic 8

Question 1

What are standard conditions

Answer 1

100kPa

298 K

Question 2

what is enthalpy change

Answer 2

the heat energy change measured at constant pressure

Question 3

exothermic enthalpy diagram

Answer 3

reactants higher than products
activation energy at top of curve
enthalpy change the distance from reactants line to products line

Question 4

endothermic enthalpy diagram

Answer 4

reactants lower than products
activation energy at top of curve
enthalpy change the difference between reactant line and product line

Question 5

standard enthalpy of reaction definition (tube sign r)

Answer 5

enthalpy change for a given reaction under standard conditions (and in the molar quantities given in chemical equation)

Question 6

standard enthalpy of formation definition (tube sign f)

Answer 6

enthalpy change when one mole is formed from elements in their standard States

Question 7

standard enthalpy of combustion definition (tube sign c)

Answer 7

enthalpy change when one mole of a substance is completely burned in oxygen under standard conditions

Question 8

standard enthalpy of neutralisation definition

tube sign neut

Answer 8

enthalpy change when one mole of water is produced from the reaction between an acid and a base under standard conditions

Question 9

measuring enthalpy changes

Answer 9

q= m x c x change in temp

-q / moles = enthalpy change

Question 10

bond breaking is

Answer 10

endothermic (requires energy)

Question 11

bond forming is

Answer 11

exothermic (releases energy)

Question 12

working out enthalpy change of a reaction

Answer 12

bond broken enthalpy - bonds formed enthalpy

Question 13

working out the rate of a reaction

Answer 13

change in concentration per second

also the gradient of a concentration time graph