energetics

Question 1

reaction system

Answer 1

products and reactants part of reaction

Question 2

surroundings

Answer 2

other things like water beaker
air bunsen burner
anything surrounding reaction

Question 3

factors that effect pressure exerted by surroundings

Answer 3

molecules in air
solution in container
lid on beaker or not

Question 4

constant pressure

Answer 4

pressure of reaction system and surroundings and pressure on system dont change

Question 5

what causes a reaction to give off heat

Answer 5

as reactants turn into products energy flows between 2.

Question 6

heat energy

Answer 6

into is taking in energy
out of is give heat

Question 7

exothermic

Answer 7

gives out energy from reaction

Question 8

endothermic

Answer 8

taking in energy from reaction

Question 9

size of arrow in energy level diagrams

Answer 9

shows how much heat energy flows between system and surroundings

Question 10

what do energy level diagrams show

Answer 10

if reaction is endothermic or exothermic and size of heat energy flow

Question 11

what to include in energy level diagrams

Answer 11

x axis energy
y axis progress of reaction
reactants and products curve

Question 12

reactions under constant pressure

Answer 12

heat energy into or out of system and changes temp of surroundings

Question 13

reactions not under constant pressure

Answer 13

changes surrounding temps and how quickly products form and how much product forms

Question 14

enthalpy change

Answer 14

change in amount of heat energy either given it or taken out from the surroundings during a reaction at constant pressure

Question 15

value of enthalpy change for exothermic

Answer 15

negative

Question 16

value of enthalpy change for endothermic

Answer 16

positive

Question 17

symbol of enthalpy

Answer 17

H

Question 18

change in symbol

Answer 18

delta

Question 19

units of enthalpy change

Answer 19

J joules

Question 20

what are standard conditions

Answer 20

atmospheric pressure 100000pa
298K

Question 21

standard enthalpy changes

Answer 21

delta H with circle on top right with line through circle

Question 22

formation reaction

Answer 22

when one mole of a substance is produced from its constituent elements under standard conditions with both reactants and products in their standard states

Question 23

enthalpy change of formation sign

Answer 23

delta small f and H

Question 24

combustion

Answer 24

substance plus oxygen is C02 plus water

Question 25

standard enthalpy of combustion

Answer 25

enthalpy change when 1 mole of a substance is completely burned in oxygen in standard conditions with all products and reactants in their standard states

Question 26

calorimetry

Answer 26

isolate objects surroundings and measure temp change

Question 27

how does mass effect temp

Answer 27

more mass is less decrease or increase of temp

Question 28

specific heat capacity

Answer 28

amount of energy it takes to increase 1g of a substance by one kelvin

Question 29

SI unit for specific capacity

Answer 29

J K-1 g-1

Question 30

q=

Answer 30

m c delta T

Question 31

calorimetry when measuring combustion reactions

Answer 31

flame calorimetry

Question 32

how to decrease heat energy loss to air

Answer 32

increase volume of water
bomb calorimeter

Question 33

calorimetry of reactions in solution

Answer 33

constant pressure calorimetry

Question 34

first type of constant pressure

Answer 34

zinc mixed with acid

Question 35

thermochemical cycle

Answer 35

shows the different possible routes that a reaction can tale from starting reactants to final products

Question 36

enthalpy change of alternative route

Answer 36

enthalpy 1 plus enthalpy two

Question 37

hess law direct quote

Answer 37

the enthalpy change in a reaction at constant pressure is independent of the route taken

Question 38

another name for alternative route reactions

Answer 38

data book reactions

Question 39

data book reactions design

Answer 39

alternative route and find total enthalpy change using data book reactions

Question 40

term enthalpy change as applied to a chemical reaction

Answer 40

heat energy change at constant pressure

Question 41

improvement to mixing two acids together for enthalpy change

Answer 41

use pipette instead of measuring cylinder
insulate beaker/ use cup
reweigh watch glass after adding solid

measure initial and final temp
time intervals

plot temp against time
extrapolate point of adding
find temp change for calculating enthalpy

Question 42

calculating final temp of enthalpy change question

Answer 42

when same find moles of chemical
take enthalpy change and times by moles
answer times 1000
100 times 4.18
divide both answers
add answer to initial temp change to get final temp

Question 43

how to improve percentage uncertainty

Answer 43

increase concentration

Question 44

equation for temp change

Answer 44

q/mc

Question 45

finding temp rise of reaction

Answer 45

find moles
times by enthalpy change
temp change is heat energy divided by total mass times specific heat capacity

Question 46

disadvantage of using glass beaker on tripod and gauze

Answer 46

glass poorer conductor than copper
tripod and gauze reduce heat transfer

Question 47

why enthalpy of combustions lower than text books

Answer 47

incomplete combustion
heat loss to surroundings

Question 48

exam questions on enthalpy of formation to enthalpy change

Answer 48

write out direct route
calculate enthalpy of formation of each elements
add formation values to diagram
add up sum of values

Question 49

if reaction balanced in combustion

Answer 49

add oxygen balanced for combustion reaction

Question 50

how to get one mole of bonds

Answer 50

times the bond enthalpy or long given number by avagadros constant

Question 51

bond dissociation enthalpy

Answer 51

energy required to break one mole of a bond in its own atoms in gaseous state

Question 52

how to find bond disscociation enthalpy

Answer 52

-take 1 mole of atom
record how many energy it takes for bond to break
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Question 53

mean bond enthalpies

Answer 53

measure the enthalpy change when 1 mole of bonds are broken taken as an mean from a range of different compounds

Question 54

how to calculate atomisation enthalpy

Answer 54

-draw out molecules
- calculate how many bonds
-calculate enthalpy from individual energy changes

Question 55

calculating heat capacity exam question

Answer 55

moles of substance
moles times amount of energy released
answer divided by temp change

Question 56

2 step reactions arrows

Answer 56

facing in a thermochemical cycle way

Question 57

formation cycle arrows

Answer 57

both facing up

Question 58

arrows in combustion cycle

Answer 58

arrows facing down

Question 59

hydrated salts arrows

Answer 59

both facing down

Question 60

how to answer hess law questions

Answer 60

write direct route equation given
-identify which type of reaction and draw thermochemical cycle according to type of reaction
-use values given to find enthalpy change for alternative routes
-label values onto thermochemical cycle
-add values together

Question 61

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