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CHEMISTRY AS > KERBOODLE SUMMARY QUESTIONS: OZ > Flashcards

KERBOODLE SUMMARY QUESTIONS: OZ Flashcards

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1
Q

State the main gases in unpolluted air

A

nitrogen
oxygen
argon

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2
Q

State three human activities that add gases to the air

A

combustion of hydrocarbons
deforestation
cattle farming
landfill
changes in land use

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3
Q

Calculate how many parts per million by volume of argon (1%) are in a typical sample of tropospheric air.

A

10 000ppm

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4
Q

Calculate the percentage of neon (18.2ppm) in a typical sample of tropospheric air

A

0.00182%

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5
Q

Calculate the volume of methane present in 1 dm3 of tropospheric air

concentration of methane in tropospheric air (1.8 ppm)

A

1.8 x 10-6 dm3

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6
Q

Calculate the percentage of methane molecules in a sample of 1 dm3 of air

concentration of methane in tropospheric air (1.8 ppm)

A

0.00018%

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7
Q

A beam of infrared radiation has an energy of 3.65 x 10-20 J per photon.

Calculate the frequency of the radiation

A

5.5 x 1013 Hz

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8
Q

A beam of X-rays has a frequency of 2.60 x 1017 s-1

Calculate the wavelength of the X-rays

A

1.15 x 10-9 m

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9
Q

Carbon dioxide is a greenhouse gas. It absorbs some of the infrared radiation given off from the Earth’s surface.

Explain why carbon dioxide molecules absorb only certain frequencies of infrared radiation

A

Specific frequencies corresponding to transitions between vibrational energy levels, making the bonds vibrate more

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10
Q

Carbon dioxide is a greenhouse gas. It absorbs some of the infrared radiation given off from the Earth’s surface.

Explain why absorbing infrared radiation makes the atmosphere warmer

A

Molecules which have absorbed radiation have more kinetic energy. This energy is subsequently transferred to other molecules in the air by collisions

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11
Q

To change 1 mole of molecular HCl from the lowest vibrational energy level (ground state) to the next vibrational level requires 32.7 kJ

Calculate the energy, in joules, gained by one molecule of HCl when energy is absorbed in this way
[Avagadro constant, NA = 6.02 x 1023 mol-1

Then calculate the corresponding frequencing of radiation. State the type of radiation this corresponds to.

Then calculate the wavelength of this radiation in metres.

A
  1. 43 x 10-20 J
  2. 20 x 10-13 Hz, infrared
  3. 66 x 10-6 m
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12
Q

You want to heat up a cup of coffee in a microwave cooker.
The cooker uses radiation of frequency 2.45 x 109 Hz
The cup contains 150 cm3 of coffee, which is mainly water.

Calculate the energy needed to raise the temperature of the water by 30oC
[specific heat capacity of water = 4.18 J g-1 K-1]

The calculate the energy transferred to the water by each photon of microwave radiation

Then calculate the energy transferred by one mole of photons

Then calculate how many moles of photons are needed to supply the energy calculated to raise the temperature of water by 30oC

A
  1. 88 x 104 J
  2. 62 x 10-24 J
  3. 978 J

19 200 moles

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13
Q

State whether or not the species F is a radical

A

yes

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14
Q

State whether or not the species Ar is a radical

A

no

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15
Q

State whether or not the species H2O is a radical

A

no

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16
Q

State whether or not the species OH is a radical

A

yes

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17
Q

State whether or not the species NO2 is a radical

A

yes

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18
Q

State whether or not the species CH3 is a radical

A

yes

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19
Q

The hydroxyl radical, HO•, is an important species in atmospheric chemistry. Reaction A shows one process in which HO• is produced. The reaction is brought about by radiation with a wavelength below 190nm.
Reaction A: H2O + hv –> H• + HO•

Hydroxyl radicals are very reactive and act as scavengers in the atmosphere. One set of reactions which involve stratospheric ozone is:

  • *Reaction B:** HO• + O3 –> HO2• + O2
  • *Reaction C:** HO2• + O3 –> HO• + 2O2

State whether reaction A is a homolytic or a heterolytic process

A

homolytic

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20
Q

The hydroxyl radical, HO•, is an important species in atmospheric chemistry. Reaction A shows one process in which HO• is produced. The reaction is brought about by radiation with a wavelength below 190nm.
Reaction A: H2O + hv –> H• + HO•

Hydroxyl radicals are very reactive and act as scavengers in the atmosphere. One set of reactions which involve stratospheric ozone is:

  • *Reaction B:** HO• + O3 –> HO2• + O2
  • *Reaction C:** HO2• + O3 –> HO• + 2O2

Explain whether reactions A, B and C are initiation, propagation or termination

A

A is initiation
B and C are propagation

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21
Q

The hydroxyl radical, HO•, is an important species in atmospheric chemistry. Reaction A shows one process in which HO• is produced. The reaction is brought about by radiation with a wavelength below 190nm.
Reaction A: H2O + hv –> H• + HO•

Hydroxyl radicals are very reactive and act as scavengers in the atmosphere. One set of reactions which involve stratospheric ozone is:

  • *Reaction B:** HO• + O3 –> HO2• + O2
  • *Reaction C:** HO2• + O3 –> HO• + 2O2

Write an equation which shows the overall result of reactions B and C

A

2O3 ⇌ 3O2

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22
Q

The hydroxyl radical, HO•, is an important species in atmospheric chemistry. Reaction A shows one process in which HO• is produced. The reaction is brought about by radiation with a wavelength below 190nm.
Reaction A: H2O + hv –> H• + HO•

Hydroxyl radicals are very reactive and act as scavengers in the atmosphere. One set of reactions which involve stratospheric ozone is:

  • *Reaction B:** HO• + O3 –> HO2• + O2
  • *Reaction C:** HO2• + O3 –> HO• + 2O2

Write an equation which shows the overall result of reactions B and C

A

2O3 ⇌ 3O2

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23
Q

The hydroxyl radical, HO•, is an important species in atmospheric chemistry. Reaction A shows one process in which HO• is produced. The reaction is brought about by radiation with a wavelength below 190nm.
Reaction A: H2O + hv –> H• + HO•

Hydroxyl radicals are very reactive and act as scavengers in the atmosphere. One set of reactions which involve stratospheric ozone is:

  • *Reaction B:** HO• + O3 –> HO2• + O2
  • *Reaction C:** HO2• + O3 –> HO• + 2O2

State the role of HO• in this process

A

catalyst

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24
Q

The creation of nitrogen monoxide from human activities is of concern because it is thought to lead to a loss of ozone from the stratosphere. Reactions D and E show how this loss can occur.

  • Reaction D:** NO• + O3 –> NO2• + O2 ΔH* = -100 kJmol-1
  • Reaction E:** NO2• + O –> O2 ΔH* = -192 kJmol-1

State one human activity which leads to the production of a significant amount of NO.

A

oxidation of nitrogen in internal combustion engines

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25
Q

The creation of nitrogen monoxide from human activities is of concern because it is thought to lead to a loss of ozone from the stratosphere. Reactions D and E show how this loss can occur.

  • Reaction D:** NO• + O3 –> NO2• + O2 ΔH* = -100 kJmol-1
  • Reaction E:** NO2• + O –> O2 ΔH* = -192 kJmol-1

Deduce the overall effect of reactions D and E.

A

O3 + O –> 2O2

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26
Q

The creation of nitrogen monoxide from human activities is of concern because it is thought to lead to a loss of ozone from the stratosphere. Reactions D and E show how this loss can occur.

  • Reaction D:** NO• + O3 –> NO2• + O2 ΔH* = -100 kJmol-1
  • Reaction E:** NO2• + O –> O2 ΔH* = -192 kJmol-1

State the role of NO in this process

A

catalyst

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27
Q

The creation of nitrogen monoxide from human activities is of concern because it is thought to lead to a loss of ozone from the stratosphere. Reactions D and E show how this loss can occur.

  • Reaction D:** NO• + O3 –> NO2• + O2 ΔH* = -100 kJmol-1
  • Reaction E:** NO2• + O –> O2 ΔH* = -192 kJmol-1

Calculat the value of ΔH for the overall process

A

(-100) + (-192) = -292 kJ mol-1

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28
Q

Reactions F to K show various processes involving ethane
Reaction F: C2H6 –> 2CH3•

Reaction G: CH3• + C2H6 –> CH4 + C2H5•

Reaction H: C2H5• –> C2H4 + H•

Reaction I: H• + C2H6 –> H2 + C2H5•

Reaction J: 2C2H5• –> C2H4 + C2H6

Reaction K: 2C2H5• –> C4H10

State whether these reactions are initiation, propagation, or termination

A
  • initiation
    • reaction F
  • propagation
    • reaction G
    • reaction H
    • reaction I
  • termination
    • reaction J
    • reaction K
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29
Q

Reactions F to K show various processes involving ethane
Reaction F: C2H6 –> 2CH3•

Reaction G: CH3• + C2H6 –> CH4 + C2H5•

Reaction H: C2H5• –> C2H4 + H•

Reaction I: H• + C2H6 –> H2 + C2H5•

Reaction J: 2C2H5• –> C2H4 + C2H6

Reaction K: 2C2H5• –> C4H10

For most of these reactions, you would need information about bond enthalpies in order to decide whether the process is exothermic or endothermic. But a few of the reactions can be classified by inspection. Explain which reactions are endothermic and which are exothermic

A
  • endothermic
    • reaction F

F is endothermic because C-C bond broken

  • exothermic
    • reaction K

K is endothemric because C-C bond is formed

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30
Q

Reactions F to K show various processes involving ethane
Reaction F: C2H6 –> 2CH3•

Reaction G: CH3• + C2H6 –> CH4 + C2H5•

Reaction H: C2H5• –> C2H4 + H•

Reaction I: H• + C2H6 –> H2 + C2H5•

Reaction J: 2C2H5• –> C2H4 + C2H6

Reaction K: 2C2H5• –> C4H10

State the names and formulae of the chemical species in the reaction sequence which are radicals

A

CH3•
methy radical

C2H5•
ethyl radical

H•
hydrogen radical

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31
Q

The radical chain reaction of methane (CH4) with chlorine in the presence of sunlight is given below:

CH4 + Cl2 –> CH3Cl + HCl

Suggest a mechanism for the reaction showing clearly which reactions correspond to the initiation, propagation, and termination stages

A

Cl2 –> 2Cl•
initiation

CH4 + Cl• –> CH3• + HCl
propagation

CH3• + Cl2 –> CH3Cl + Cl•
propagation

Cl• + Cl• –> Cl2
termination

CH3• + CH3• –> C2H6
termination

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32
Q

The radical chain reaction of methane (CH4) with chlorine in the presence of sunlight is given below:

CH4 + Cl2 –> CH3Cl + HCl

Explain why the reaction product also contains some CH2Cl, CH3Cl and CCl4

A

The chloromethane can react with Cl• radicals

CH3Cl + Cl• –> CH2Cl• + HCl
CH2Cl• + Cl2 –> CH2Cl2 + Cl•

Further substitution produces CHCl3 and CCl4

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33
Q

Use the collision theory to explain why coal burns faster when it is finely powdered than when it is in a lump

A

Greater surface area, so more frequent collisions

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34
Q

Use the collision theory to explain why nitrogen and oxygen in the atmosphere do not normally react to form nitrogen oxides

A

Insufficient energy to overcome the activation energy

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35
Q

Use the collision theory to explain why reactions between two solids take place very slowly

A

Particles are in fixed positions and number of collisions is low

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36
Q

Use the collision theory to explain why flour dust in the air can ignite with explosive violence

A

Very high surface area and a spark will easily overcome the activation energy

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37
Q

The collision theory assumes that the rate of a reaction depends on:

  • *A:** the rate at which reactant molecules collide with one another
  • *B:** the proportion of reactant molecules that have enough energy to react once they have collided

Which out of A and B, explains that reactions in solution go faster at higher concentrations

A

A: the rate at which reactant molecules collide with one another

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38
Q

The collision theory assumes that the rate of a reaction depends on:

  • *A:** the rate at which reactant molecules collide with one another
  • *B:** the proportion of reactant molecules that have enough energy to react once they have collided

Which out of A and B, explains that solids react faster with liquids or gases when their surface area is greater

A

A: the rate at which reactant molecules collide with one another

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39
Q

The collision theory assumes that the rate of a reaction depends on:

  • *A:** the rate at which reactant molecules collide with one another
  • *B:** the proportion of reactant molecules that have enough energy to react once they have collided

Which out of A and B, explains that catalysts increase the rate of reactions

A

B: the proportion of reactant molecules that have enough energy to react once they have collided

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40
Q

The collision theory assumes that the rate of a reaction depends on:

  • *A:** the rate at which reactant molecules collide with one another
  • *B:** the proportion of reactant molecules that have enough energy to react once they have collided

Which out of A and B, explains that increasing the temperature increases the rate of a reaction

A

Mainly B: the proportion of reactant molecules that have enough energy to react once they have collided

with A to a minor extent A: the rate at which reactant molecules collide with one another

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41
Q

For the reaction of magnesium with hydrochloric acid

Mg(s) + 2HCl(aq) –> MgCl2(aq) + H2(g)

State which of the following factors might affect the rate

A) temperature

B) total pressure of gas

C) concentration of solution

D) surface area of solid

A

A, B, C and D

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42
Q

For the reaction of nitrogen with hydrogen in the presence of an iron catalyst

N2(g) + 3H2(g) –> 2NH3(g)

State which of the following factors might affect the rate

A) temperature

B) total pressure of gas

C) concentration of solution

D) surface area of solid

A

A and B

43
Q

For the decomposition of aqueous hydrogen peroxide

2H2O2(aq) –> 2H2O(l) + O2(g)

State which of the following factors might affect the rate

A) temperature

B) total pressure of gas

C) concentration of solution

D) surface area of solid

A

A, B and C

44
Q

A mixture of hydrogen and oxygen doesn’t react until it is ignited by a spark - then it explodes. The mixture also explodes if you add some powdered platinum

The energy of a spark is tiny, yet it is enough to ignite any quantity of a hydrogen/oxygen mixture, large or small.
Suggest an explanation for this.

A

The reaction has a high activation enthalpy that prevents it occuring at a significant rate at room temperature. However, the reaction is exothermic and once the spark has provided the energy needed to get it started, the reaction produces enough energy to sustain itself regardless of how much is present.

45
Q

A mixture of hydrogen and oxygen doesn’t react until it is ignited by a spark - then it explodes. The mixture also explodes if you add some powdered platinum

Explain why platinum makes the hydrogen/oxygen reaction occur at room temperature

A

The platinum catalyst offers an alternative pathway with a lower activation enthalpy close to the thermal energy of molecules at room temperature

46
Q

The activation enthalpy for the decomposition of hydrogen peroxide to oxygen and water is +36.4 kJ mol-1 in the presence of an enzyme catalyst and +49.0 kJ mol-1 in the presence of a very fine colloidal suspension of platinum. The overall reaction is exothermic.

Sketch, on the same enthalpy diagram, the enthalpy profiles for both cataylsts

A

Reaction profile shows reactants at higher enthalpy than products, and two lines showing activation enthalpy for uncatalysed reaction higher than activation enthalpy for catalysed reaction

X-axis: progress of reaction, y-axis: enthalpy. Ea for cataylsed reaction marked as +36.4 kJ mol-1 and for uncatalysed marked as +49.0 kJ mol-1.

47
Q

The activation enthalpy for the decomposition of hydrogen peroxide to oxygen and water is +36.4 kJ mol-1 in the presence of an enzyme catalyst and +49.0 kJ mol-1 in the presence of a very fine colloidal suspension of platinum. The overall reaction is exothermic.

How will the rate of the decomposition of hydrogen peroxide differ for the two catalysts at room temperature?
Explain your answer

A

The rate will be faster for the catalysed reaction as the activation enthalpy is significantly lower, so more molecules have sufficient energy to react.

48
Q

The enthalpy profiles A-D represent four different reactions - all diagrams are drawn to the same scale

State which of the enthalpy profiles A-D represents exothermic reactions

A

B and C

49
Q

The enthalpy profiles A-D represent four different reactions - all diagrams are drawn to the same scale

State which of the enthalpy profiles A-D represents endothermic reactions

A

A and D

50
Q

The enthalpy profiles A-D represent four different reactions - all diagrams are drawn to the same scale

State which of the enthalpy profiles A-D shows the largest activation enthalpy

A

D

51
Q

The enthalpy profiles A-D represent four different reactions - all diagrams are drawn to the same scale

State which of the enthalpy profiles A-D shows the smallest activation enthalpy

A

B

52
Q

The enthalpy profiles A-D represent four different reactions - all diagrams are drawn to the same scale

State which of the enthalpy profiles A-D represents the most exothermic reaction

A

B

53
Q

The enthalpy profiles A-D represent four different reactions - all diagrams are drawn to the same scale

State which of the enthalpy profiles A-D represents the most endothermic reaction

A

D

54
Q

The reaction of chlorine atoms with ozone in the upper atmosphere (stratosphere) is thought to be responsible for the destruction of the ozone layer:
Cl + O3 –> ClO + O2

The chlorine atoms are produced by the action of high energy solar radiation on CFCs.
Use collision theory to explain how an increase in the concentration of chlorine atoms increases the rate of reaction with ozone.

A

Increases in concentration mean more collisions so that there are more collisions with the minimum energy to react

55
Q

The reaction of chlorine atoms with ozone in the upper atmosphere (stratosphere) is thought to be responsible for the destruction of the ozone layer:
Cl + O3 –> ClO + O2

The chlorine atoms are produced by the action of high energy solar radiation on CFCs.
The activation enthalpy for the reaction of chlorine atoms with ozone is relatively small. Explain what effect you would expect a change of temperature to have on the rate of this reaction

A

As the activation enthalpy is small, an increase in temperature will mean that many more collisions will have the minimum energy to react and so the rate of reaction increases rapidly

56
Q

The diagram below shows the energy distribution for collisions between Cl atoms and O3 molecules at temperature T1. Ea is the activation enthalpy for the reaction of Cl atoms and O3 molecules. Copy the diagram and shade the area of the graph to indicate the number of collisions with sufficient energy to lead to a reaction

A

The shaded area in underneath the T1 curve and to the right of Ea

57
Q

The diagram below shows the energy distribution for collisions between Cl atoms and O3 molecules at temperature T1. Ea is the activation enthalpy for the reaction of Cl atoms and O3 molecules.
Indicate the energy distribution for collisions between Cl atoms and O3 molecules when the temperature of the reactants is increased by 10 K to T2. Shade the area under the graph to indicate the number of collisions with sufficient energy to lead to a reaction at T2

A

The area shaded is underneath the T2 curve and to the right of Ea. The T2 curve has a lower and broader maximum than the T1 curve and the maximum value is shifted to the right. It tails off above the T1 curve.

58
Q

The breakdown of ozone in the stratosphere is catalysed by chlorine atoms. The overall reaction is:

O3 + O –> 2O2

The Cl atoms act as a homogeneous catalyst in this process.
State the meaning of the term homogeneous

A

Homogeneous means same physical state. Here the catalyst and reactants are gases

59
Q

The breakdown of ozone in the stratosphere is catalysed by chlorine atoms. The overall reaction is:

O3 + O –> 2O2

The Cl atoms act as a homogeneous catalyst in this process.
The enthalpy profiles for the catalysed and uncatalysed reactions are shown below.

Explain why the enthalpy profile for the catalysed reaction has two humps

A

It is a two step reaction with an activation energy for each step

60
Q

The breakdown of ozone in the stratosphere is catalysed by chlorine atoms. The overall reaction is:

O3 + O –> 2O2

The Cl atoms act as a homogeneous catalyst in this process.
The enthalpy profiles for the catalysed and uncatalysed reactions are shown below.

Describe what is happening at the peaks and troughs on the two curves

A

peaks: enough energy has been put in to start the reaction
troughs: intermediate step

61
Q

Name the haloalkane CHCl3

A

trichloromethane

62
Q

Name the haloalkane CH3CHClCH3

A

2-chloropropane

63
Q

Name the haloalkane CF3CCl3

A

1,1,1-trichloro-2,2,2-trifluoroethane

64
Q

Name the haloalkane CH3-CHCl-CF3

A

2-chloro-1,1,1-trifluoropropane

65
Q

Name the haloalkane CH3-CHCl-CBr2-CH3

A

2,2-dibromo-3-chlorobutane

66
Q

Explain why noble gases have very low boiling points

A

In the solid or liquid state, noble gas atoms are held together by weak instantaneous dipole - induced dipole bonds. It takes very little energy to break these bonds and this results in very low melting and boiling points

67
Q

Draw skeletal formulae showing how two molecules of pentane can approach close to one another. Now do the same for both of its structural isomers, 2-methylbutane, and 2,2-dimethylpropane

A
68
Q

Explain the boiling points of the isomers below in terms of the strength of the intermolecular bonds present

A

Pentane is a straight-chain and its molecules can approach each other closely so there are strong intermolecular forces

Methylbutane and dimethylpropane have respectively more branching and cannot approach as closely, so the instantaneous dipole - induced dipole forces are weaker

The stronger the intermolecular bonds, the more energy is required to break them

69
Q

Explain the difference in strength of the intermolecular bonds of the isomers below

A

Pentane has the strongest intermolecular bonds and hence the highest boiling point. Dimethylpropane has the weakest intermolecular bonds and hence the lowest boiling point

70
Q

Explain whether CO2 possesses a permanent dipole, considering the shape of the molecule and the electronegativity of its atoms

A

no dipole

71
Q

Explain whether CHCl3 possesses a permanent dipole, considering the shape of the molecule and the electronegativity of its atoms

A

dipole

72
Q

Explain whether C6H12 (cyclohexane) possesses a permanent dipole, considering the shape of the molecule and the electronegativity of its atoms

A

no dipole

73
Q

Explain whether CH3OH possesses a permanent dipole, considering the shape of the molecule and the electronegativity of its atoms

A

dipole

74
Q

Explain whether (CH3)2CO possesses a permanent dipole, considering the shape of the molecule and the electronegativity of its atoms

A

dipole

75
Q

Explain whether benzene possesses a permanent dipole, considering the shape of the molecule and the electronegativity of its atoms

A

no dipole

76
Q

Silane, SiH4, boils at 161 K whereas hydrogen sulfide, H2S, boils at 213 K

State the number of electrons in each molecule

A 
SiH<sub>4</sub> = 18
H<sub>2</sub>S = 18
77
Q

Silane, SiH4, boils at 161 K whereas hydrogen sulfide, H2S, boils at 213 K

Explain the strengths of instantaneous dipole - induced dipole bonds in the two compounds

A

The attractions will be similar because the number of electrons is the same

78
Q

Silane, SiH4, boils at 161 K whereas hydrogen sulfide, H2S, boils at 213 K

Explain whether either molecule possesses a permanent dipole

A

H2S has a permanent dipole - it is a bent molecule with two lone pairs. SiH4 does not have an overall permanent dipole as it is a symmetrical molecule

79
Q

Silane, SiH4, boils at 161 K whereas hydrogen sulfide, H2S, boils at 213 K

Explain the different boiling points of these two compounds

A

Both compounds have similar instantaneous dipole - induced dipole bonds
However H2S also has permanent dipole - permanent dipole bonds
So its boiling point is higher than that of SiH4

80
Q

Explain why the O-H bond is polar.

A

Oxygen is more electronegative than hydrogen

81
Q

State whether or not the covalent bond C-F will be polar. If so, show which atom is positive and which is negative using the 𝛿+ and 𝛿- convention

A

C𝛿​+–F𝛿-
polar

82
Q

State whether or not the covalent bond C-H will be polar. If so, show which atom is positive and which is negative using the 𝛿+ and 𝛿- convention

A

C–H
non polar

83
Q

State whether or not the covalent bond C-S will be polar. If so, show which atom is positive and which is negative using the 𝛿+ and 𝛿- convention

A

C–S
non polar

84
Q

State whether or not the covalent bond H-Cl will be polar. If so, show which atom is positive and which is negative using the 𝛿+ and 𝛿- convention

A

H𝛿+–Cl𝛿-
polar

85
Q

State whether or not the covalent bond H-N will be polar. If so, show which atom is positive and which is negative using the 𝛿+ and 𝛿- convention

A

H𝛿+–N𝛿-
polar

86
Q

State whether or not the covalent bond S-Br will be polar. If so, show which atom is positive and which is negative using the 𝛿+ and 𝛿- convention

A

S–Br
non polar

87
Q

State whether or not the covalent bond C-O will be polar. If so, show which atom is positive and which is negative using the 𝛿+ and 𝛿- convention

A

C𝛿+–O𝛿-
polar

88
Q

Hydrogen bonding can occur between different molecules in mixtures. Draw a diagram to show where the hydrogen bonds form in a NH3 and H2O mixture

A
89
Q

Hydrogen bonding can occur between different molecules in mixtures. Draw a diagram to show where the hydrogen bonds form in a CH3CH2OH and H2O mixture

A
90
Q

Explain why water exhibits a greater degree of hydrogen bonding than other substances

A

Water has two O-H bonds and two lone pairs on the oxygen so more hydrogen bonding is possible

91
Q

When 1-chloropropane is heated under reflux with aqueous sodium hydroxide solution, a nucleophilic substitution reaction occurs, forming propan-1-ol

Write a balanced equation for this reaction

A

CH3CH2CH2Cl(l) + NaOH(aq) –> CH3CH2CH2OH(aq) + NaCl(aq)

92
Q

When 1-chloropropane is heated under reflux with aqueous sodium hydroxide solution, a nucleophilic substitution reaction occurs, forming propan-1-ol

Explain why this is a substitution reaction

A

The chlorine atom in 1-chloropropane has been replaced by a hydroxyl group, OH.

93
Q

When 1-chloropropane is heated under reflux with aqueous sodium hydroxide solution, a nucleophilic substitution reaction occurs, forming propan-1-ol

Draw the mechanism of the reaction, showing the relevant lone pairs and partial charges

A

Curly arrow from lone pair of electrons on OH- to carbon in C-Cl bond
Curly arrow from C-Cl bond to chlorine.
Propanol and Cl- formed
𝛿+ on carbon of C-Cl and 𝛿- on chlorine of C-Cl bond

94
Q

Write balanced equations for the nucleophilic substitution reaction of iodoethane and OH- ions, showing the structures of the reactants and products clearly

A

C2H5I + OH- –> C2H5OH + I-

95
Q

Write balanced equations for the nucleophilic substitution reaction of bromoethane and CN- ions, showing the structures of the reactants and products clearly

A

C2H5Br + CN- –> C2H5CN + Br-

96
Q

Write balanced equations for the nucleophilic substitution reaction of chlorocyclopentane and OH- ions, showing the structures of the reactants and products clearly

A

C5H9Cl + OH- –> C5H9OH + Cl-

97
Q

Write balanced equations for the nucleophilic substitution reaction of 2-chloro-2-methylpropane and H2O, showing the structures of the reactants and products clearly

A

CH3C(CH3)ClCH3 + H2O –> CH3C(CH3)(OH)CH3 + HCl

98
Q

Write balanced equations for the nucleophilic substitution reaction of 1,2-dibromoethane and OH- ions, showing the structures of the reactants and products clearly

A

CH2BrCH2Br + 2OH- –> CH2OHCH2OH + 2Br-

99
Q

Write balanced equations for the nucleophilic substitution reaction of bromomethane and C2H5O- (ethoxide) ions, showing the structures of the reactants and products clearly

A

CH3Br + C2H5O- –> CH3OC2H5 + Br-

100
Q

Write balanced equations for the nucleophilic substitution reaction of 2-chloropropane and CH3COO- (ethanoate) ions, showing the structures of the reactants and products clearly

A

CH3CHClCH3 + CH3COO- –> CH3CH(OOCCH3)CH3 + Cl-

101
Q

Concentrated ammonia solution reacts with 1-bromoethane when heated in a sealed tube

Write a balanced equation for this reaction

A

CH3CH2Br + NH3 –> CH3CH2NH2 + H+ + Br-

102
Q

Concentrated ammonia solution reacts with 1-bromoethane when heated in a sealed tube

Draw out the mechanism for this reaction

A
103
Q

Concentrated ammonia solution reacts with 1-bromoethane when heated in a sealed tube

How would you explain the mechanism of this reaction in words

A

Ammonia is the nucleophile because of its lone pair. It attacks the partial positive charge on the carbon atom and substitutes the bromine atom. There is a partial positive charge because bromine is more electronegative than carbon. After the NH3 attacks the 1-bromoethane, a hydrogen ion is lost from the molecule to give the product ethylamine

104
Q

Concentrated ammonia solution reacts with 1-bromoethane when heated in a sealed tube

Give definitions of nucleophile, electronegativity, substitution, and curly arrow

A

Nucleophile: a species with a lone pair that can form a covalent bond
Electronegativity: the power to attract electrons in a covalent bond
Substitution: where one atom or group replaces another atom or group
Curly arow: device to show the movement of a pair of electrons

CHEMISTRY AS (24 decks)

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