PPQS Flashcards
(158 cards)
1
Q
Suggest whteher clf3 HAS polar bonds
A
YES
- F more electronegative
- d+ cl, d- f
2
Q
electronegativity
A
ability of an atom to attract the electronS in a covalent bond
3
Q
why do repeats?
A
- increase repeatability
- find anomalies AND DISCARD
4
Q
atomic emission spectra provisde evidence for …
A
quantum shells
5
Q
6 MARKS
Problems and improvements of collection over water(gas collected 2 low)
A
- gas escapes from apparatus. use airtight bung with gas syringe
- metal covered with an oxide. clean with abrasive BEFORE weighing
- mass of metal used too low. use a more PRECISE balance
6
Q
shortest bond length in CH3OH
A
O-H as largest difference in electronegativity
7
Q
hydrogen bond angle
A
ALWAYS 180
- 2 bonding pairs
- 0 lone pairs
8
Q
trigonal bipyrmaidal angles
A
- 5 bp, 0 lp
- 90 and 120
9
Q
explain why the positive charge is on the carbon atom shown
A
tertairy carbocation is more stable than a primary carbocation
because it has more positive inductive alkyl groups
10
Q
importance of termination (2)
A
- 2 free radicals join together
- dont form any free radicals
11
Q
describe what is meant by cracking (2)
A
- use of high temperatures
- to break large molcules into smaller molecules, ,and produce alkenes
12
Q
why can propene form 2 possible products with HBr
A
- asymmetric alkene
- Br could join to c1 or c2
- to form 1 bromo or 2 bromo propane
13
Q
biggest hazard of alkanes
A
flamable
14
Q
in combustion where must the u-tube go
A
BEFORE boiling tube w lime water; distinguishes water as a product of combustion rather than the limewater
15
Q
why can hydrogen chloride gas not conduct electricity but HCl acid can
A
covalent bond in hydrogen chloride changes to an ionic bond in aqueous solution
16
Q
pressure in pvnrt is in
A
PASCALS
17
Q
EXPLAIN WHY METHANOL IS SOLUBLE IN WATER
A
- hydrogen bonding between them both
- of same strength
- comparable to the strength of the bonding in either component on its own
18
Q
why is NaCL soluble in water but not methanol
A
- hydration of BOTH ions in water
- but ionic bonding is stronger than bonding between ions and methanol
19
Q
2 reasons why x is more electronegative
A
- more protons
- smaller atomic radius
20
Q
despit ehaving polar bonds why is x not polar
A
- symmetricak
- BOND POLARITIES CANCEL
21
Q
use mexwell boltzmann diagram to explain why the use of a catalyst increases the rate of decomposition of ammonia (3)
A
- area under curve represents fraction of molecules with E>= Ea
- area with Ea of catalyst is greater; more molecules have E>= Ea
- more freqeunt successful collision
22
Q
similarities (2) and differences (2) between pi and sigma bonds
A
SIMILARITIES:
- both include the overlap of orbitals
- both involve electrostatic attraction between a BONDING pair of electrons and positive nuclei
DIFFERENCES:
- pi = sideways overlap of orbitals
- sigma = direct end on overlap of atomic orbitals
23
Q
explain maxwell boltzmann at high temp
A
- peak shifts to the right and lower
- at higher temperatures there are more particles with higher energy
24
Q
why might reaction not happen as shown
A
- might react with oxygen
- unlikely for reactants to be in correct ratio
- reaction must occur in a series of steps as too many particles reacting in equation
25
+- of chemical test vs infrared to show alcohol
+
cheaper
rapid
can be done in schools
-
CHEMICAL TEST NOT AS SENSITIVE
26
vol gas a bit higher at higher temp
gases expand when heated
27
why is the measurement of initial rate less accurate than max
- difficult to judge where tangent should be drawn for 0
- compared to other points on the line
28
why is a heterogeneous catalyst good for gas reactant
provides a surface for the reaction
29
why might uncertainty of someone else be hgiher with mass measurement
they used a smaller mass w same balance
30
why does catalyst not effect amount of product made
increases rate of forward and backward reactions
31
why is catalyst heated and why might it melt
- heated to provide activation energy
- metls as bonds broken
32
advatnage of catalyst iN INDUSTRY
- decreases activation energy
- allows milder conditions to be used (lowering cost)
33
chromate (VI) ion colour
YELLOW
34
WHY IS ice less dense than water
- water molecules in a lattice
- molecules further apart in ice than water
35
TMS purpose
reference peak to compare other shifts to
36
what does NMR actually do
change spin state of hydrogen nuckeus
37
effect of increasing temp on rate constant
increases
38
why is there at least 2 steps (RDS REFERENCE)
- x and y in RDS (z not in)
- but more reactants in full equation
- so must be another step containing z
39
why is the major product from the tertiary carbocation
- most stable
- inductive effect of alkyl groups
40
why are the other reactant concnetrations in hUGE excess in iodine clock reaction
- concentration remain constant
- so that [I2] is limiting reagent; only its concnetration changes
-OTHERWISE A CURVE IS OBTAINED AS FULL ORDER OF REACTION
41
how to measure order of propanone as 1st order after already doing one step of iodine
- doulbe conc of propanone
- rate should double (gradient doubkes)
OR
- measure conc propanone over time
-constant half life
42
how to quench iodine TITRATION
- add NAHCO3
- neutralizes acid
43
sodium hydrogencarbonate neutralising ACID catalyst ionic equation
HCO3- + H+ = H2O + CO2
44
why is mols of soidum thiosulfate v low
- so concentration of reactants doesnt fall significantly before end point reached
- used up during initial rate period
45
quenching with IODINE CLOCK method
- take samples at various times
- quench with ice
- titrate using alkali
46
why might u get anomalies where rate is too high
- rate is too high
- reaction exothermic
- more collisions with E>= Ea
47
what happens if no thiosulfate added in iodine clock
reaction goes blue black immediately
48
purpose of thiosulfate
- as soon as iodide reacts to form iodine, thio reacts to turns it back to iodide
- to prevents colour change occuring until a set amuont of reaction occured
49
how to use colorimetry for iodoine(3)
- colorimetry
- measure absorbance
- CALIBRATION CURVE to turn it into concentration. absorbance proprotional to concentration
50
biggest alkane hazard
TOXIC BY INHALATION
51
reforming defition
converting straight chain HC to a ring/branched
52
cracking defintion
breaking a longer HC to shorter chain HC
53
describe waht happens to pi and sigma bonds in addition
- pi bond breaks
- sigma bond remains
- as pi weaker
- forms a carbocation intermediate
54
alkene with acidificed potassium manganate (7)
DILUTE SULFURIC ACID
- forms a DIOL
- purple to colourless
55
a fuel is ...
a substance that produces energy
56
why might the fuels be liquified
easier to transport
57
hazard vs risk
hazard: potential to do harm
risk: likelihood harm will result
58
which o the 2 ions has POLARIZING ability
cation
59
formation of acid rain rain on limestone
REACTS with limestone to corrode buildings
60
why conducgtivity different (ionic compounds)
cations are diff sizes
61
why cant silicon conduct electricity
- outer electorns FIXED in covalent bonds
- no delocalised electrons
62
why are polymers not sustainable
made from crude oil which is non-reneweable
63
why is pi weaker than sigma
- sigma direct end on overlap of orbitas- along line in between the 2 nuclei
- pi = sideways overlap
64
why is ice less dense than water
- molecules spread out further apart
- in a lattice
- h bonds longer than covalent bonds
65
why non polar insoluble n water
cant h bond with water
66
ionic compounds solubility
- soluble in water, ions hydrated
- enthalpy change of hydration compensates for energy needed to break part lattice
- INSOLUBE in non polar as any forces that would form between ion and substance weaker than ionic bondng
67
describe the structure of. metal (3)
- lattice
- positive metal cations in layer
- sea of delocalised electrons
68
electrolyss of CuCrO4
- ions migrate
- Cu2+ blue colour towards cathode
- CrO4 2- yellow colour towards anode
69
2 sources of repulsion in ionic lattice
- ions of same charge repel
- positive nuclei repel
70
purpose of reforming
- more efficient combustion
- fuels with a higher octane number
- NO KNOCKING
71
why might volume co2 be slightly lower
- sligthyl soluble in water
72
using a smaller cylinder multiple times vs a bigger one once
1. look at error/ncertainty
2. more time taken to refill loads
3. GREATER TRANSFER LOSSES
73
why does distillation work
- difference in bp
- the one with lower bp boils and vaporises first, so can be condensed and then collected
74
purpose of reflux
- reactants vapourise, then condense
- return to reaction mixture
- allows to reach BP without LOSS OF REACTANT
75
HOW TO DISTILLATE TO GET PURE PRODUCT
1. heat
2. collect distillate
3. at BP of the prducrt
76
c-c with bromine vs c=c
1. c-c sigma only
2. strong bond, need to break c-h aswell
3. c=c sigma and pi
4. e- desnity above and below plane, polarises br-br
5. pi bond weaker so easier to break
77
2 conditions for cracking
1. high temp
2. silica catalyst
78
conditions for haloalkane and ammonia and why
- heat in a sealed vessel
- increases pressure to increase rate of reaction]
- but prevents loss of product
79
purpose of needing ethanol with the water and AgNO3 for haloalkane test
- cosolvent
- dissolves both haloalkane AND water
80
BP 2 chloro 2 methyl propane
50-52
81
rate of hydrolysis primary, secondary, tertiary
primary slowest
82
orbital
- a region where there is a high probaility of finding electrons
- holds up to 2 electrons with opposite spins
83
explain why 1st electron affinity is negative but second is positive
1. negative as exothermic due to attraction between POSTIIVE nucleus and electron
2. postivie as endothermic as energy required to overcome
3. repulsion between negative ion and electron
84
assumptions for theoretiacl lattice energy (2)
- 100% ionic bonding
- ions are perfect spheres
85
final comment for the theoretical lattice energy questions
- more energy released when making the bond, so bond is stronger, and LE more exothermic
86
2 problems with free radical substitution
1. cant control number of cl that will substiutte; oversubstitution
2. mixture of products will form, need to separate
87
) Explain why benzene is resistant to bromination but ethene reacts readily
with bromine at room temperature.
1. ethene c=c, electron density localised
2. electron density delocalised in pi structure of benzene
3. high ea for benzene as energy needed to break structure
4. ethene more susceptible to electrophilic attack
88
length hydrogen bonds compared to covalent
LONGER
89
BIGGEST DIFFERENCE BETWEEN ACID HYDROLYSIS OF ESTER AND ALKALI
acid: acid is catalyst
alkali: alkali is a REACTANT
90
why are condensation polymers biodegradable
ESTSER link can be hydrolysed by enzymes
91
temperature conditions for nitration of benzene and why
- below 55
- PREVENTS MULTIPLE SUBSTITUTIONS
92
Why is organic synthesis with less steps more eco frendly
higher yield
93
reaction to form no2 + for nitration of benzene
HNO3 + 2H2SO4 = 2HSO4- + NO2+ + H3O +
94
if Kp is x^2/y, discuss effect of incrasing pressure
- increases partial pressure of numerator more than denominator as squared
- so the mole fraction of y increases
- to resotre Kp
95
why hard to measure temp endo
difficult to measure temperature whilst heating
96
describe what happens when copper sulfate dissolves in water
- ionic lattice broken
- water hydrates each ion
97
why is HF boiling point the most
- F is MOST ELECTRONEGATIVE ELEMENT
- So stronger hydrogen bond
98
2 problems with NOx that arent ghg
- dissolve in water to form acid rain
- breathing problems
99
bond angle ice and water
different
100
eg Kc is 1
there are more moles of products than reactants explain
1. calculat new Kc; Kc >1
2. moles products must decrease AND moles reactants must increase to restore Kc
3. POE shifts to the left
101
test for halide
HNO3
AgNO3
102
WHAT SHAPE IS CATALYTIC CONVERTER AND WHY
- honeycomb
- increases SA
- allows gases to flow through
103
why cant distillation make ethanioc acid
- ethanol oxidised to ethanal
- low bp, distilled of as soon as formed
- before full oxidation to ethanoic acid
104
why would rate of reaction with oxygen decrease in a sealed vessel
concentration of oxygen decreases
105
ratio of 35 Cl 2 , 35Cl37Cl, 37Cl2
9:6:1
106
which apparatus for oxidation to ketone
- reflux
- to ensue full oxidation
107
why might a temperature reading be wrong
- mixture not stirred so temperature not unifor
108
who burns wiwth a sooty flame
greater c:h
eg alkenes
109
what does having a methyl group on the benzene ring do
INCREASE electron density
- positive inductive effect
110
if organic synthesis q, increase carbon chain how?
- if x1 : CN
- if loads: polymer
- if by a specific number of C : GRIGNARD
111
in complete oxidation the oxidising agent is
in excess
112
why might you get Cl 36 in mass spec
[35Cl37Cl]2+
m/z 36
113
steps of recrytallisation
- dissolve impure in MINIMUM volume of hot solvent
- filter it hot through a preheated funnel
- cool in ice bath + stir with glass rod
- vaccum filtration (buchner filtration)
- RINSE WITH ICE COLD ETHANOL
- dry between filter paper
114
distillation vs separating funnel
distillation: difference in BOILING POINTS
separating funnel: immiscible liquids
115
if one H+ is used in the reaction but 2 are produced, can it still be a catalyst?
YES
- One is regenerated, so thats the catalyst
- one is a product of the reaction
116
recrystallisation: why cool in ice bath
- product is less soluble in colder solutions so will crystallise out
117
recrystallisation: why warm filtering
- to prevent crystallisation
- which would reduce yeild
118
recrystallisation: why buchner filtration
- removes remaining solution (soluble impuirities) faster
- dryer crystals
119
problem if you have impurities in a gaseous reaction with a heterogeneous catalyst (3)
- impurities ADSORB onto surface of catalyst, occupying active sites
- fewer active sites avilable for reactants to adsorb
- IMPURITIES LESS LIKELY TO DESORB
120
purpose of TMS
- calibration
- to compare other hydrogen shifts
121
explain why you can get pcl5 but not ncl5
- PCl 5 can expand its octet
- NCl5 cannot as no d orbital
122
when halogenating with PCL5 , THE CONDITINO IS
anhydrous
123
how to classify something as an addition reaction
- 2 things react together
- only 1 product
124
colour of NO2
red brown gas
125
what acc happens when you add potassium manganate to an alkene
goes to a DIOL
126
3 suitable drying agents
CaCl2
MgSO4
Na2SO4
127
porblems with using a toxic fine powder
- risk of inhalation
- wear a face mask
128
consequence of condesner filled wrong
- air bubbles form
- less efficient cooling
- loss of reaction mixture
129
why do you need a condenser
PREVENT ESCAPE OF GAS
130
COMPARING SIMPLE DISTILLATION EQUIPMENT TO GOOD DISTILLATION EQUQIPMENT
SIMPLE:
- easy and chepaer to set up
- less efficient cooling
- gases will escape
BETTER:
- can check temp
- will condnse the vapour preventing escape
- therefore prederred AS can confirm when the product is being distilled and condenser ensures safe collection
131
how to ensure crystals reach the bottom of the tube
flick the tube
132
what is used as the liquid in the thiele tube and why ? (3)
1. dibutyl phthalate
2. HIGH BP
3. does not decompose at high temp
133
134
does oxygen react w sodium hydroxide
no
135
does co2 react with sodium hydroxide
yes
136
problem measuring temperature change of endo reation
difficult to measure temperature decrease whilst heating
137
problem with measuring temperature change of exothermic
- difficult to measure temperature of solid
-
138
Describe the processes that occur when solid copper(II) sulfate dissolves in water.
1. ionic lattice broken
2. ions hydrated
139
why does HF have higher mp than NH3
- similar LF
- both h bonds but
HF stronger as fluorine is MORE ELECTRONEGATIVE than N
140
why does x method give greater yeild
ONE STEP VS 2 STEP
- only forms one isomer
141
2 problems with the oxidese of nitrogen
- asthma
- dissolve in water to form acid rain
142
explain why pH increases so rapidly at the start of weak acid strong base titration (2)
- conc HA > conc A-
- ratio A- : HA changes in this region
-
143
hwen in doubt, assumption for acid base is:
conc acid initial = conc acid eqm
144
explain in terms of Kp what happens if u increase pressure
- increases num/denom more than the other
- Kp must be constant
- so mf of (prod or react) must increase/decrease
145
x ray diffraction in benzene
shows c-c all the same length
146
in sulfuric acid nitric acid describe their roles
sulfuric acid acts as acid , protonates the nitric acid which acts as a base
147
amine functional group
r-n-r
148
phenyl amine from nitrobenzene
- tin
- concentrated sulfuric acid
- SEPARATE WITH STEAM DISTILLATION
149
cu+ in nh3
[cu(nh3)2 ]+
colourless
150
MnO4 - and C2O4 2- reaction
- rate slow as they repel as negatively charged
- when Mn2+ formed, they catalyse the reaction
- Mn2+ REDUCES MnO4- to Mn3+
- and then mn3+ oxidises c2o4 2- to reform Mn2+
151
problem with metal oxides
- corrosive
react with silicone dioxide
forms INERT SILICATES
152
purpose of starch in iodine clock
- indicator
- turns blue black when all of thiosulfate ran out
- use TIME TAKEN for the blue black as an end point to calc initial rate
153
for the rate in halogenoalkane why use water and not oh-
oh- + ag would form ag(oh) ppt
154
WHY is eletrode potential mn2+ more positive than fe2+
- 3d5 half filled subshell more stable
- mn2+ has this so is more stable than mn3+
- fe3+ has this so is more stable than fe2+, also has pair of e- that repel so less stable
155
why are metals malleable but not ionic copounds?
- in a metal the layers of positive ions can slide over
one another (1)
* and sea of delocalised electrons between the
layers prevents repulsion between the ions in
one layer and those in another layer (1)
* in sodium chloride when a layer of ions is
displaced, ions with the same charge become close to one another and repel
156
burette uncertainty
0.05
157
2 dp balance uncertainty
0.005
158
