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edexcel igcse chemistry > unit three: physical chemistry > Flashcards

unit three: physical chemistry Flashcards

(117 cards)

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1
Q

what is the test for lithium

A

dip a nichrome wire in hydrochloric acid to clean it,,. pick up some of the crystals on the wire and hold them on the edge of a blue bunsen flame.

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2
Q

what is the observation when testing lithium

A

a bright red flame

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3
Q

what is the test for sodium

A

dip a nichrome wire in hydrochloric acid to clean it,,. pick up some of the crystals on the wire and hold them on the edge of a blue bunsen flame.

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4
Q

what is the observation when testing sodium

A

yellow flame

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5
Q

what is the test for potassium

A

dip a nichrome wire in hydrochloric acid to clean it,,. pick up some of the crystals on the wire and hold them on the edge of a blue bunsen flame.

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6
Q

what is the observation when testing calcium

A

orange-red flame

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7
Q

what is the test for calcium

A

dip a nichrome wire in hydrochloric acid to clean it,,. pick up some of the crystals on the wire and hold them on the edge of a blue bunsen flame.

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8
Q

what is the test for copper

A

dip a nichrome wire in hydrochloric acid to clean it,,. pick up some of the crystals on the wire and hold them on the edge of a blue bunsen flame.

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9
Q

what is the observation when testing copper

A

green flame

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10
Q

what is the test for aqueous copper

A

add aqueous sodium hydroxide a drop at a time to form a precipitate.

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11
Q

what is the observation when testing aqueous copper

A

blue precipitate

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12
Q

what is the test for aqueous iron (II)

A

add aqueous sodium hydroxide a drop at a time to form a precipitate.

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13
Q

what is the observation when testing aqueous iron (II)

A

green precipitate

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14
Q

what is the test for aqueous iron (III)

A

add aqueous sodium hydroxide a drop at a time to form a precipitate.

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15
Q

what is the observation when testing aqueous iron (III)

A

brown precipitate

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16
Q

how do you test for ammonia

A

add aqueous sodium hydroxide to the solid or solution under test and warm the mixture

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17
Q

what is the observation when testing for ammonia

A

a pungent-smelling gas is produced. the gas produced turns damp red litmus paper blue

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18
Q

what is the test for chlorine

A

to an aquous solution of the solid under test, add some dilute nitric acid followed by a few drops of silver nitrate solution.

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19
Q

what is the observation when testing for chlorine

A

white precipitate

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20
Q

what is the observation when testing for bromine

A

cream precipitate

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21
Q

what is the test for bromine

A

to an aquous solution of the solid under test, add some dilute nitric acid followed by a few drops of silver nitrate solution.

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22
Q

what is the test for iodine

A

to an aquous solution of the solid under test, add some dilute nitric acid followed by a few drops of silver nitrate.

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23
Q

what is the observation when testing for iodine

A

yellow precipitate

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24
Q

what is the test for sulphate

A

to an aqueous solution of the solid under test, add dilute hydrochloric acid followed by a few drops of barium chloride solution

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25
what is the observation when testing for sulfate
white precipiate
26
what is the test for carbonate
to either the solid, or an aqueous solution of the solid under test add dilute hydrochloric (or nitric) acid.
27
what is the observation when testing for carbonate
bubbles of gas. the gas produced turns limewater milky.
28
Q =
m x c x Δt
29
ΔH =
Q / n
30
exothermic
energy is given out
31
endothermic
energy is taken in
32
example of an exothermic reaction
the reaction between sulfuric acid and magnesium
33
example of an endothermic reaction
the reaction between sodium hydrogen carbonate and citric acid
34
what is specific heat capaacity
the amount of heat needed to raise the temperature of a substance by 1 degree celsius
35
specific heat capacity of water
4.18 J/g/degree celsius
36
breaking bonds
needs energy
37
making bonds
releases energy
38
what does anhydrous mean
without water
39
if you heat blue copper sulfate crystals until they turn to a white powder and then and water to it again what happens
it turns blue again and is very warm.
40
what is the reversible reaction symbol
⇌
41
if you heat ammonium chloride what happens
the white crystals disappear from the bottom of the tube and reappear further up. it splits it into the colourless gasses ammonia and hydrogen chloride
42
the stronger the bond
the more energy is required to break it
43
what are bond energies measured in
kJ/mol
44
is breaking bonds endo or exothermic
it needs energy, so endothermic
45
is making bonds endo or exothermic
it releases energy so exothermic
46
which type of substance are bond energy calculations used for
covalent molecules
47
if the sign of the overall bond energy calculation is negative what does it mean
heat is given out as the bonds rearrange. the reaction is exothermic
48
if the sign of the overall bond energy calculation is positive what does it mean
heat has been absorbed as the bonds rearrange, the reaction is endothermic
49
what is a closed system
no substances are added to the reaction mixture and no substances escape from it. heat may be lost or absorbed.
50
what is dynamic equilibrium
rate of forward reaction = rate of backward reaction
51
what is the forward reaction
left to right
52
what is the backward reaction
right to left
53
when does the position of equilibrirum lie to one direction
if the reaction is at equilibrium but htere is more of the left substance than the right substance then the position of equilibrium lies to the left, and vice versa
54
how would you change rate of reaction
change pressure change temperatyre add a catalyst (this has no effect on the position of equilibrium)
55
exothermic changes apart from burning:
the reactions of metals with acids neutralisation reactions displacement reactions
56
what is enthalpy change
the amount of heat energy taken in or given out in a chemical reaction
57
enthalpy is the difference between
energy of the products and energy of the reactants
58
does endothermic have a negative or positive enthalpy change
a positive because the reactants are absorbing heat
59
does exothermic have a negative or positive enthalpy change
negative because the reactants are losing heat
60
how do you make a substance decompose
heat it constantly
61
what is specific heat capacity
the amount of heat needed to raise the temperature of 1 gram of substance by 1 degree
62
is combustion a endothermic or exothermic reaction
exothermic reaction
63
major errors in evaluation of experimental results for enthalpy changes
large amounts of heat loss | could be incomplete combustion
64
how can you tell if an alcohol is combusting completely
the flame should be blue and carbon dioxide should be produced instead of carbon
65
how can you tell if an alochol is combusting incompletely
the flame of the wick is often yellow orange and carbon is produced.
66
what does (in) excess mean
more than enough of a reactant is present to ensure all of the other reactant(s) react
67
breaking bonds is
endothermic
68
making bonds is
exothermic
69
what are bond energies measured in
kJ/mol
70
bond energy definition
the amount of energy needed to break 1 mole of covalent bonds in gaseous molecules
71
what does a sealed container/closed system mean
no substances are added to the reaction mixture and no substances escape from it. heat can be given off or absorbed.
72
define dynamic equilibrium
the total amounts or concentrations of the reactants and products are now constant.
73
give features of dynamic equilibrium (5)
rate of forward reaction = rate of backward reaction closed system the concentrations of the reactants and products don't need to be equal the concentrations of the reactants and products must remain constant concentration change in the reaction
74
the reaction from left to right is the
forward reaction
75
the reaction from right to left is the
backward reaction
76
what does the position of eqilibrium mean
a reference to the proportion of the reactants and products in an equilibrium mixture. if the position of a reaction lies towards the right, the equilibrium mixture contains a higher proportion of products than reactants.
77
what things would you change in an attempt to influence the reaction
change the pressure change the temperature add a catalyst
78
effect of increasing pressure on a reaction in equilibrium
the position of equilibrium shifts to the side which has fewer gas molecules
79
effect of decreasing pressure on a reaction in equilibrium
the position of equilibrium shifts to the side which has fewer gas molecules.
80
effect of increasing temperature on a reaction in equilibrium
the position of equilibrium shifts in the endothermic direction
81
effect of decreasing temperature on a reaction in equilibrium
the position of equilibrium shifts in the exothermic reaction
82
how would you make a reaction of hydrated to anhydrous substance happen
heat it
83
how would you make a reaction of anhydrous to hydrated substance happen
add water
84
specific heat capacity of water
4.18
85
moles =
mass / Mr
86
moles =
solution volume x concentration
87
symbol for enthalpy change
ΔH
88
symbol for energy change
Q
89
moles =
gas volume / 24
90
sources of error in combustion calorimetry
heat loss to surroundings heat loss to apparatus incomplete combustion (CO or C formed instead of CO2 evaporation of fuel (hot fuel escapes after burner extinguished)
91
energy change for reaction (energetics) =
energy change in breaking bonds - energy change in making bonds break - make
92
unit for specific heat capacity?
J/g°C or J/kg°C
93
what type of reaction is thermal decompistion
endothermic
94
why do reactions either give out or absorb heat
during chemical reactions bonds in the reactants have to be broken and new ones have to be
95
breaking bonds...
needs energy
96
making bonds...
releases energy
97
what is the rate of a reaction
the speed at which the amount of reactants decreases or the amount of products increases
98
what is rate measured as
a change in the concentration (or amount) of reactants or products per unit time
99
rate of reaction =
change in conc, volume or mass ----------------------------------------------------------------- time
100
the steeper the slope/line,
the faster the reaction
101
how can you measure how fast the reaction is going at any point
by finding the slope (gradient) of the line at that point)
102
how do you explain the shape of the curve on a graph
using collision theory
103
what is activation energy
the particles have to collide with a minimum amount of energy in order for a reaction to actually happen.
104
what are successful collisions
the collisions with energy greater than or equal to the activation energy
105
when the graph's line is flat or horizontal what does it mean
all of one of the reactants have been used up, so the reaction has stopped
106
why are reactions faster if the solids present are in lots of pieces
the surface area in contact with the gas or liquid is larger and there are more particles if the solid exposed on the surface. only the particles on the surface are available for collisions. the frequency of successful collisions increases as the surface area of the solid increases.
107
what is a catalytic converter
it uses expensive metals such as platinum coated onto a honeycomb structure in a very thin layer for maximum possible surface area.
108
what happens if you reduce the concentration of an acid or alkali in a reaction
the reaction slows
109
why does the reaction slow down when concentration is reduced
the number of acid particles decrease, are therefore less close together and collide less frequently. there are fewer succcessful collisions every second.
110
why does increasing temperature speed up the rate of reaction
the particles are moving faster and so collide more frequently. that will make the reaction go faster, but it only accounts for a small part of the increase in rate. it also increases the number of particles with energy greater or equal to the activation energy, so it will be more likely that two particles which have sufficient energy will collide and react with each other, so frequency of successful collisions increases.
111
why does increasing pressure increase rate of reaction
it forces particles closer together so that they collide more frequently.
112
why does decreasing pressure decrease rate of reaction
it allows particles to spread out so frequency of successful collisions decreases.
113
what are catalysts
substances that speed up chemical reactions but arent used up in the process. they remain chemically unchanged at the end of the reaction.
114
do different reactions use different catalysts
yes
115
what are enzymes
biological catalysts
116
how can you show that a substance is chemically unchanged by the end of a reaction
weigh it before and after you add it to the catalyst solution. the mass should not have changed.
117
how does a catalyst work
it provides an alternative route for the reaction involving a lower activation energy.

edexcel igcse chemistry (4 decks)

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