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chem 2 Flashcards

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1
Q

Aspirin can also be produced by reacting 2-hydroxybenzenecarboxylic acid with

ethanoyl chloride.
State why ethanoic anhydride is preferred to ethanoyl chloride for this preparation.

A

Ethanoic anhydride/It is less/not corrosive

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2
Q

Give the name of the mechanism for the reaction of

2-hydroxybenzenecarboxylic acid with ethanoic anhydride.

A

addition-elimination

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3
Q

Suggest the role of the concentrated phosphoric acid.

A

catalyst

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4
Q

Suggest why reflux is not essential when the flask is heated to 85 °C for 10 minutes.

A

boiling points are above 85 °C

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5
Q

Suggest the identity of two impurities present in the filtered solid aspirin before it is washed

A
  • ethanoic acid
  • phosphoric acid
  • 2-hydroxybenzenecarboxylic acid
  • ethanoic anhydride
  • water
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6
Q

Describe the recrystallisation process used to purify the aspirin.

Include the method and apparatus used.

A

M1 Dissolve crude product in hot solvent (water and ethanol)
M2 of minimum volume
M3 Filter (hot to remove insoluble impurities)
M4 Cool (to recrystallise)
M5 Filter under reduced pressure / with Buchner/Hirsch apparatus
M6 wash (with cold solvent) and dry

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7
Q

State the physical property that is measured to check the purity of the aspirin.
Describe two ways the result would show that the product is impure.

A

M1 melting point
M2 lower (than data book value)
melts over a (wide) range of temperature (rather than
sharp/narrow range if pure)

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8
Q

Suggest why a loose cotton wool plug is placed in the neck of the flask, instead of leaving the flask open or inserting a bung.

A

(instead of leaving the flask open) to avoid acid/solution/liquid
escaping

(instead of inserting a bung) to allow gas/CO2 to escape

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9
Q

2 20 g of large marble chips is a large excess of calcium carbonate.

Suggest why using a large excess of calcium carbonate means that the rate is only
affected by the changing concentration of the hydrochloric acid.

A

so that surface area/mass/amount stays (approx./effectively)
constant

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10
Q

In this experiment the variable measured is mass loss.

The rate of this reaction at a constant temperature can be investigated in other ways.
Suggest two other variables that can be measured instead of mass loss.

A
  • volume of gas / CO2
  • pH
  • concentration of HCl/acid/H+
  • conductivity
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11
Q

Propanoic acid is a weak acid.

State the meaning of weak in this context.

A

partially dissociates / does not fully dissociate (into ions) / ionise
(when added to water / in aqueous solution)

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12
Q

Suggest why a student doing an experiment to produce the curve in Figure 4 would
add the sodium hydroxide solution dropwise around the equivalence point.

A

as there is a large pH change (for a small addition of alkali)

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13
Q

0 4 . 5 When sodium hydroxide solution is added to aqueous propanoic acid, the solution
formed acts as a buffer when between 5 cm3 and 15 cm3 have been added.
Explain why the pH stays approximately constant during this part of the experiment.

A

M1 OH–
reacts with propanoic acid
ratio of [CH3CH2COOH] to [CH3CH2COO– remains almost constant

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14
Q

Methyl orange and universal indicator are not suitable indicators for the titration of solutions of propanoic acid with sodium hydroxide.
State the reason why each indicator is not suitable.

A

M1 methyl orange – would not change colour at the equivalence
point (allow end-point) / pH range does not match rapid pH
change / pH range does not include/match equivalence point

M2 universal indicator – idea of range of colours during titration /
no distinct colour change (at equivalence/end-point)

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15
Q

Which row contains two species with different numbers of electrons?

[1 mark]

A NH3 and HF
B CO3
2– and NO3
–
C H3O+ and HF2
+
D CH4 and NH2

A

H3O+ and HF2
+

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16
Q

Which element has the highest third ionisation energy?

[1 mark]

A Li
B Be
C K
D Ca

A

Be

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17
Q

0 8 Compound P is converted into compound R by a two-stage synthesis via

compound Q.
The yields for the individual steps are:
P → Q 50%
Q → R 30%
What is the overall yield of R in this synthesis?

A 15%
B 30%
C 40%
D 80%

A

15%

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18
Q

What is the formula of ammonium ethanedioate?

[1 mark]

A NH4(C2O4)2
B (NH4)2C2O4
C NH4C2O4
D (NH4)2(C2O4)3

A

(NH4)2C2O4

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19
Q

Which substance does not have any bond angles of 120°?

[1 mark]

A benzene
B boron trifluoride
C cyclohexane
D graphite

A

cyclohexane

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20
Q

1 2 Which molecule does not have a permanent dipole?
[1 mark]

A NH3
B PCl3
C SCl2
D SiCl4

A

SiCl4

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21
Q

Which compound forms the greatest number of hydrogen bonds per molecule in the

liquid state?

[1 mark]

A CH3CH2COOH
B CH3CH2OCH3
C CH3CH2CHO
D CH3CH2CH2OH

A

CH3CH2COOH

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22
Q

What is represented by the total area under the curve?

[1 mark]

A The total energy of the molecules in the reaction mixture
B The total energy of reacting molecules in the reaction mixture
C The total number of molecules in the reaction mixture
D The total number of reacting molecules in the reaction mixture

A

The total number of molecules in the reaction mixture

23
Q

1 6 Which statement explains why the rate of a reaction increases when a catalyst is

added at a constant temperature?

[1 mark]

A The collision frequency increases because there is a decrease in
activation energy.

B The collision frequency increases because there is an increase in the
average energy of the particles.

C The proportion of successful collisions increases because there is a
decrease in activation energy.

D The proportion of successful collisions increases because there is an
increase in the average energy of the particles.

A

c
The proportion of successful collisions increases because there is
a decrease in activation energy.

24
Q

A cell with EMF = +2.15 V is made from two electrodes.
The half-equations for the two electrodes are shown.

positive electrode:
PbO2(s) + 3H+(aq) + HSO4
–
(aq) + 2 e–

⟶ PbSO4(s) + 2H2O(l)

negative electrode:
PbSO4(s) + H+(aq) + 2e– ⟶ Pb(s) + HSO4
–
(aq) Eo = –0.46 V

What is the standard electrode potential of the PbO2 / PbSO4 electrode?

[1 mark]

A –2.61 V
B –1.69 V
C +1.69 V
D +2.61 V

A

1.69 v

25
Q

1 8 Values of the ionic product of water (Kw) at different temperatures are given.

Kw = 6.40 × 10–15 mol2 dm–6 at 18 °C
Kw = 1.00 × 10–14 mol2 dm–6 at 25 °C
Which statement is correct?

[1 mark]

A The concentration of hydroxide ions in water at 18 °C is
8.00 × 10–8 mol dm–3

B The dissociation of water into ions is an exothermic process.

C The pH of water is the same at 25 °C and at 18 °C

D Water becomes less acidic as the temperature is raised.

A

The concentration of hydroxide ions in water at 18 °C is 8.00 × 10– 8 mol dm–3

26
Q

Consider the Period 3 elements from sodium to chlorine.

Which statement is correct?

[1 mark]

A Sodium has the smallest atomic radius.
B Aluminium has the highest melting point.
C Sulfur is the most electronegative.
D Chlorine has the highest first ionisation energy.

A

Chlorine has the highest first ionisation energy.

27
Q

Which statement correctly describes a trend down Group 7 from Cl to I?

X represents Cl, Br or I

[1 mark]

A The boiling point of HX increases.

B The bond dissociation energy of H–X increases.

C The standard electrode potential value for X2(aq) + 2 e–
⟶ 2X–
(aq) becomes more positive.

D The solubility of AgX in ammonia increases.

A

The boiling point of HX increases.

28
Q

2 1 Which statement about chloride ions is correct?
[1 mark]

A They are oxidised by concentrated sulfuric acid.

B They form a cream precipitate with silver nitrate solution.

C They form a cobalt(II) complex with a tetrahedral shape.

D They have the electron configuration 1s2
2s2
2p6
3s2
3p4

A

C They form a cobalt(II) complex with a tetrahedral shape

29
Q

Aqueous aluminium sulfate is added to aqueous sodium carbonate.
What are the formulas of the precipitate and the gas formed?

[1 mark]

A Al2(CO3)3 and SO2
B Al2(CO3)3 and CO2
C Al(H2O)3(OH)3 and SO2
D Al(H2O)3(OH)3 and CO2

A

Al(H2O)3(OH)3 and CO2

30
Q

What is the correct structural formula for 4-chloro-2-methylpent-2-enoic acid?
[1 mark]

A CH3CCl=CHCH(CH3)COOH
B (CH3)2C=CHCHClCOOH
C CH3CHClCH=C(CH3)COOH
D (CH3)2CHCH=CClCOOH

A

CH3CHClCH=C(CH3)COOH

31
Q

2 4 In which conversion does a nucleophile attack the organic reactant?
[1 mark]

A CH3CH2CH3 ⟶ CH3CHClCH3
B CH3CH=CH2 ⟶ CH3CHBrCH3
C CH3CH2CH2OH ⟶ CH3CH=CH2
D CH3CH2CHO ⟶ CH3CH2CH(OH)CN

A

CH3CH2CHO ⟶ CH3CH2CH(OH)CN

32
Q

Compound Y has the structural formula CH3COOCH2CH(CH3)2

Which compound is a position isomer of Y?

[1 mark]

A 5-hydroxyhexan-3-one
B butyl ethanoate
C hexanoic acid
D propyl propanoate

A

propyl propanoate

33
Q

Which compound shows E–Z isomerism?

[1 mark]

A 2,3-dimethylbut-1-ene
B 2,3-dimethylbut-2-ene
C 2-methylpent-2-ene
D 3-methylpent-2-ene

A

3-methylpent-2-ene

34
Q

2 7 What is the product when 3-methylbutan-2-one reacts with acidified KCN?
[1 mark]

A 2-hydroxy-2,3-dimethylbutanenitrile
B 3-hydroxy-2,3-dimethylbutanenitrile
C 2-hydroxy-3-methylpentanenitrile
D 3-hydroxy-2-methylpentanenitrile

A

2-hydroxy-2,3-dimethylbutanenitrile

35
Q

Which statement concerning nylon-6,6 is correct?

[1 mark]

A Butanedioic acid is one of the reactants used to make nylon-6,6
B Nylon-6,6 is an addition polymer.
C Nylon-6,6 can be hydrolysed by aqueous sodium hydroxide.
D All molecules of nylon-6,6 have the same relative molecular mass.

A

Nylon-6,6 can be hydrolysed by aqueous sodium hydroxide.

36
Q

Which statement about the industrial production of ethanol from ethene at 300 °C is

correct?

C2H4(g) + H2O(g) ⇌ C2H5OH(g) ΔH = –46 kJ mol–1

[1 mark]

A The use of an acid catalyst increases the yield of ethanol.
B The reaction is slower than fermentation.
C An increase in temperature, at constant pressure, increases the
value of Kp.
D An increase in pressure, at constant temperature, increases the
equilibrium yield of ethanol.

A

An increase in pressure, at constant temperature, increases the
equilibrium yield of ethanol.

37
Q

3 0 Which compound is formed by the acid hydrolysis of phenyl benzenecarboxylate?
[1 mark]

A C6H5CH2OH
B C6H5CHO
C C6H5COCH3
D C6H5COOH

A

C6H5COOH

38
Q

Which type of polymer is most difficult to hydrolyse?

[1 mark]

A polyalkene
B polyamide
C polyester
D protein

A

polyalkene

39
Q

In which polymer does hydrogen bonding occur between the polymer chains?
[1 mark]

A a polyalkene
B a polyamide
C a polychloroalkene
D a polyester

A

a polyamide

40
Q

Use evidence from the rate equation to explain why Step 1 is the

rate determining step.

A

Step 1 includes CH3COCH3 and OH– and these are also in the rate
equation

41
Q

Explain why the amount of S increases when water is added to the

equilibrium mixture.

A

M1 equilibrium shifts to side with most moles
M2 to oppose decrease in concentration of all reactants and products
/ dilution of everything

42
Q

Cracking can also be done without a catalyst, using a temperature of 1200 K and a

pressure of 7000 kPa
State the type of product that is formed in high percentage in this type of cracking.

A

alkene

43
Q

Natural gas is used in power stations to produce electricity.

Natural gas contains sulfur impurities. Sulfur dioxide forms when these impurities are
burned.
State an environmental problem caused by sulfur dioxide.
Give the formula of a compound that is used to help remove sulfur dioxide from the
combustion products.

A

acid rain
M2 CaO or CaCO3

44
Q

This method is used to prepare a sample of ester F.
Step 1 Mix 10 cm3 of propan-2-ol with 10 cm3 of ethanoic acid.
Add 5 drops of concentrated sulfuric acid.
Reflux this reaction mixture for 20 minutes.
Step 2 Transfer the cooled reaction mixture to a separating funnel.
Add 20 cm3 of aqueous sodium carbonate and shake the mixture.
Step 3 Transfer the organic layer to a beaker and add 5 g of
anhydrous magnesium sulfate.
Decant off the organic liquid.
Step 4 Collect the ester using simple distillation.

0 4 . 2 Describe how Step 1 should be done.
In your description you should
* give details of suitable equipment used to add each reagent to the reflux apparatus
* draw a labelled diagram of the apparatus used for refluxing the reaction mixture
* explain any safety precautions needed other than eye protection.

A

1a Measuring cylinder(s) for the propan-2-ol and
ethanoic acid (size not required but if specified
should be between 10 - 100 cm3
)
Allow 10cm3 / graduated pipette or burette
1b (Dropping/teat) pipette for sulfuric acid (NOT
graduated or other qualification for pipette)

2a Labelled condenser shown vertical and open at
top and bottom i.e. in cross section
2b Labelled water in at the bottom and water out at
the top of the vertical condenser
2c Labelled reaction flask recognisable as either
pear shaped or round bottomed
3a Use a fume cupboard / fume hood / well-
ventilated lab space

AND to avoid breathing in harmful / toxic / corrosive
compounds
3b Wear gloves
AND as compounds are corrosive
3c Add glass beads/chips (to the mixture before
heating) / labelled as anti-bumping granules/chips
AND to ensure smooth boiling / reduce size of
bubbles
3d Use an electric heater/water bath
AND as compounds are flammable

45
Q

0 4 . 3 In Step 2 the reaction mixture from Step 1 is shaken with aqueous sodium carbonate.

State the purpose of the sodium carbonate.
Suggest a precaution that should be taken while this mixture is shaken in the
separating funnel.
Give a reason for your suggested precaution.

A

M1 To neutralise / remove / react with (excess) acid
M2 Remove stopper/bung OR tip the funnel upside down and open
the tap
M3 There will be a build up of pressure / gas / carbon dioxide

46
Q

Give the reason for the use of anhydrous magnesium sulfate in Step 3.

A

drying agent

47
Q

Suggest how the purity of the ester can be confirmed during the distillation in Step 4.

A

Compare boiling point to a data book/known value

48
Q

Silver nitrate solution can be used to distinguish between

propanoyl chloride and 1-chloropropane.
Give the observations you would expect when a few drops of silver nitrate solution are
added to separate samples of propanoyl chloride and 1-chloropropane.

[2 marks]

Observation with propanoyl chloride

Observation with 1-chloropropane

A

M1 Misty / white / steamy fumes
M2 No visible change

49
Q

Three unlabelled bottles are known to contain either propan-1-ol, propanal, or

propanone.
A sample of each liquid is warmed with a few drops of Fehling’s solution.
Identify the liquid that reacts with Fehling’s solution and give the expected
observation.
Suggest a further simple test-tube reaction that can be used to distinguish between
the remaining two liquids.
Give the expected observation with the liquid that reacts.

A

Propanal AND (blue solution gives a brick) red precipitate

(Warm with)
acidified
potassium
dichromate (VI)

add Na

warm with a named
carboxylic acid with
conc H2SO4

(Warm with)
acidified potassium
manganate (VII)

M3
Propan-1-ol /
alcohol
AND
(orange
solution) goes
green

Propan-1-ol/
alcohol
AND
effervescence

Propan-1-ol /
alcohol
AND
fruity smell

Propan-1-ol /
alcohol
AND
(purple solution)
goes colourless

50
Q

Explain why Step 4 produces a racemic mixture.

A

M2 Equal chance (50/50) attack from above/below OWTTE
M3 Giving equal amounts of both optical isomers/enantiomers

51
Q

Explain why P is a stronger base than Q.

A

M1 The lone pair on nitrogen in P is more available or more able to
accept protons/H+
M2 more alkyl groups are electron releasing/donating

52
Q

State a possible use for the amine formed in Step 2.

A

Manufacture of dyes/(cationic) surfactants/fabric softener

53
Q

Suggest reasons for the differences between the values obtained by each of
Methods 2 and 3, and the value obtained by Method 1 in Table 3.

A

M1 Value from calorimetry less exothermic / lower / smaller (than
method 1 value)
M2 (Calorimetry = ) because of heat / energy loss
M3 (Calorimetry = ) incomplete combustion
M4 (Calorimetry = ) some liquid hydrocarbon could have evaporated
M5 Mean bond enthalpies values use enthalpies taken across a
range of compounds
M6 Value from bond enthalpy data ignores energy changes in
vaporisation of the fuel or condensing the water

54
Q
A

chem (34 decks)

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