Energetics

Question 1

what ∆H does exothermic reactions have

Answer 1

negative

Question 2

what ∆H does endothermic reactions have

Answer 2

positive

Question 3

what is standard enthalpy of combustion

Answer 3

minimum enthalpy change when one mole of a compound is completely burned in oxygen in their standard state

Question 4

what is standard enthalpy of formation

Answer 4

minimum enthalpy change when one mole of a compound is formed in their standard states

Question 5

what are standard conditions

Answer 5

100kpa and 25degrees

Question 6

what is specific heat capacity

Answer 6

unique to each chem it is the amount of energy required to raise 1g by 1*c/K

Question 7

what is equation used in calorimetry

Answer 7

q=mc∆T

Question 8

what is hess law

Answer 8

the enthalpy change for a reaction is independent of the route taken

Question 9

cheat code for drawing hess cycles

Answer 9

• given ∆x
• top equation opposite to given
• arrows match given
• if given ∆fH write components
• if given ∆cH write ‘burned products’

Question 10

what way do arrows go in formation

Answer 10

up

Question 11

what way do arrows go in combustion

Answer 11

down

Question 12

what is the mean bond enthalpy

Answer 12

the enthalpy change when one mole of bonds of the same type is broken averaged over a wide variety of compounds

Question 13

which type of bond is exothermic

Answer 13

making

Question 14

which type of bond is endothermic

Answer 14

breaking

Question 15

what is mean bond enthalpy calculation

Answer 15

sum of bond broken - sum of bonds formed

Question 16

what is the difference between a hess cycle value and a mean bond enthalpy

Answer 16

specific bonds in specific compound each have their own unique enthalpy. mean bonds enthalpy is averaged over a wide variety of compounds