Deans Community High School
Science Department
Higher Chemistry
Unit 1 – Energy Matters
Homework Booklet
1
Unit 1
1.1 Rates of Reaction
1. The graph below shows the volume of hydrogen given off when a 2 cm long strip
of magnesium ribbon (mass 0.1 g) was added to an excess of 1 mol l–1 hydrochloric
acid solution.
80
70
60
Volume of gas
50
(cm3)
40
30
20
10
0
5
10
15
20
25
30
Time (seconds)
35
40
45
50
a) Calculate the average rate of reaction (Show your working)
i) over the first 10 seconds.
ii) between 10 seconds and 20 seconds.
4
b) i) How does the rate change as the reaction proceeds. .....................................................
ii) Explain this change in rate.
1
...................................................................................................
................................................................................................................................................................
c) After what time does the reaction stop? ..............................................................................
1
1
d) Draw a labelled diagram of the apparatus that could be used in this experiment.
2
2
e) Copy the graph shown above,
i) add the curve you would expect to get when 0.1 g of magnesium powder had been
used instead of 0.1 g of magnesium ribbon.
2
ii) add the curve you would expect to get if 0.05 g of magnesium ribbon had
been added to an excess of 2 mol l–1 hydrochloric acid solution.
2
2. The overall rate of a chemical reaction is often taken as the reciprocal of time
(1/time). Graphs of reaction rate against concentration and reaction rate against
temperature are shown below.
Graph 1
Graph 2
a) From graph 1
i) Calculate the time taken for the reaction when the concentration is 0.4 mol l-1.
2
ii) Explain why the rate increases as the concentration increases. .............................................
..................................................................................................................................................................... 1
b) From graph 2
i) Find the temperature rise needed to double the reaction rate ..........................................
1
ii) Explain why a small temperature rise can give a large increase in reaction rate.
..................................................................................................................................................................
....................................................................................................................................................................
Total = 18
3
1
1.2 Energy Diagrams
1. The diagram shows the distribution of kinetic energies in a sample of gas at 20°C.
number of
molecules
kinetic energy of the molecules (kJ)
a) Copy the diagram and add another line to show the kinetic energy distribution of
the molecules at 30°C.
1
b) Draw a line to represent the activation energy of a reaction which is slow at 20°C.
1
c) With reference to the completed diagram explain why an increase of temperature
of 10°C can lead to a large increase in reaction rate.
...................................................................................................................................................................
...................................................................................................................................................................
2
2. What is meant by the term ‘activation energy”? .......................................................................
................................................................................................................................................................... 1
3. What is meant by the term ‘activated complex’. ”? .................................................................
................................................................................................................................................................... 1
4.
Potential
energy
(kJ)
reaction pathway
a)i) Is this an endothermic or an exothermic reaction? .............................................................
ii) Explain your answer.
1
.................................................................................................................
...................................................................................................................................................................
4
1
b) What is the value of:
i) the activation energy for the forward reaction?
..........................................................
1
ii) the enthalpy change for the reaction?
...........................................................
1
iii) the energy of the activated complex?
...........................................................
1
c) The reaction shown can be speeded up by the use of a suitable catalyst.
What effect does a catalyst have on
5.
i) the enthalpy change for the reaction?
............................................................
1
ii) the activation energy for the forward reaction
.............................................................
1
2HI(g)
H2(g) + I2(g)
The reaction above is reversible. The activation energy for the forward reaction is
80 kJ and the reverse reaction is 50 kJ.
a) Copy and complete the graph below to show how the potential energy varies as the
reaction
proceeds.
160
140
Potential
energy
(kJ)
120
100
80
60
reactants
40
20
0
reaction pathway
b) Is the forward reaction is exothermic or endothermic. ............................................ 1
c) Gold and platinum both catalyse the reaction. For the forward reaction EA
using gold is 30 kJ, while EA using platinum is 40 kJ.
i) using different dotted lines add this information to the graph.
ii) which is the better catalyst for the reaction? Explain your choice.
...........................................................................................................................................
d) The gold and platinum catalysts are used in the solid state. Are the catalysts
heterogeneous or homogeneous catalysts? Explain your choice. .........................
.................................................................................................................................................
5
Total = 20 marks
2
2
2
1.3 Rates of Reaction
1. An oil company leaflet on “Unleaded Motoring” gives the following advice.
‘Cars fitted with catalytic converters must use unleaded petrol only’
Explain the reason for this advice.
.........................................................................................
................................................................................................................................................................... 2
2. a) Describe in terms of adsorption how a heterogeneous catalyst works. ......................
...................................................................................................................................................................
...................................................................................................................................................................
................................................................................................................................................................... 2
b) Describe how a catalyst poison stops a catalyst working.
...........................................................................................................................................................
............................................................................................................................................................ 1
3.
800
Potential
energy
(kJ)
600
400
200
Reaction pathway
a) What is the activation energy for
i) the forward reaction?
..................................................................
ii) the back reaction?
..................................................................
2
b) What is the enthalpy change for the formation of products? ...................................
1
c) Is this reaction endothermic or exothermic? Explain your answer.
...........................................................................................................................................................
............................................................................................................................................................
1
d) Copy the diagram and add a dotted line to show the effect of using a catalyst.
1
e) Mark with an X the position where the activated complex would be formed.
1
6
4. The effect of temperature on reaction rate can be studied using the reaction between
oxalic acid and acidified potassium permanganate solution.
(a) What colour change would indicate that the reaction was complete? .................
.................................................................................................................................................
1
(b) A student’s results are shown on the graph below.
(i) Use the graph to calculate the reaction time, in s, at 40oC.
(ii) Why is it difficult to obtain an accurate titration time when the reaction is
carried out at room temperature?
1
.................................................................................................................................................... 1.
Total = 14 marks
7
1.4 Enthalpy Changes
1.
a) Write a balanced equation for the complete combustion of propane.
..............................................................................................................................................
1
b) Using the enthalpy of combustion of propane given in the data booklet calculate the
amount of heat energy given out when 5.5 g of propane is completely burned.
3
2. Calculate the temperature rise when 500 cm of water at 18°C is heated by
completely burning 2.2 g of propane. (Assume no heat losses. Take the
specific heat capacity of water to be 4.18 kJ kg–1 oC–1, and use the heat of
combustion of propane given in the data booklet).
3. When 0.1 g of ethanol (C2H5OH) is burned in oxygen the heat energy given out
raised the temperature of 500 cm3 of water from 20.3oC to 21.7oC.
Calculate the enthalpy of combustion, in kJ mol-1, of ethanol.
2
3
3
8
4. When 10g of potassium bromide (KBr) was dissolved in water the temperature of 100 cm3
of water fell from 20.1oC to 15.9oC.
Using this data along with the specific heat capacity of water given in the data booklet,
calculate the enthalpy of solution of potassium bromide.
3
-1
3
5. When 100cm of 1 mol l hydrochloric acid was reacted with 100cm of 1 mol l
potassium hydroxide the temperature of the mixture rose by 6.5oC.
Calculate the enthalpy of neutralisation.
-1
3
6. The enthalpies of combustion of methanol (CH3OH), ethanol (C2H5OH) and propanol
(C3H7OH) are –726, -1370 and –2020 kJ mol-1 respectively.
a) i) Why is there a regular increase in the ethalpies of combustion from methanol to
propanol?
...................................................................................................................................................................... 1
ii) Estimate the enthalpy of combustion of butanol (C4H9OH).
....................................
1
b) Calculate the amount of heat energy given out by the complete combustion of
1.6g of methanol.
2
c) i) Draw a labelled diagram of the apparatus you would use in the laboratory to
estimate the enthalpy of combustion of methanol.
ii) Give two reasons why the value obtained using this apparatus is less than the
accepted value given in the data booklet. ............................................................................
...........................................................................................................................................................
9
Total = 18 marks
2
1.5 Patterns in the Periodic Table
1. Explain the change in covalent radius of the elements
a) across the Periodic table from lithium to fluorine. ..............................................................
................................................................................................................................................................ 2
b) down group 1 from lithium to caesium. ........................................................................................
................................................................................................................................................................ 2
2. Explain why a Na+ ion is larger than a Mg2+ ion. ...........................................................................
................................................................................................................................................................
................................................................................................................................................................ 2
3. Explain a calcium, Ca2+ ion is larger than a Mg2+ ion. .................................................................
................................................................................................................................................................
................................................................................................................................................................ 2
4. a) What is meant by the first ionisation energy of an element? ..........................................
................................................................................................................................................................ 1
b) Explain why the ionisation energy is an endothermic process .........................................
................................................................................................................................................................ 1
c) Write an equation corresponding to the first ionisation energy of Aluminium
................................................................................................................................................................ 1
d) Explain why the first ionisation energy of fluorine is greater than the first
ionisation energy of lithium. ......................................................................................................
................................................................................................................................................................
................................................................................................................................................................ 2
e) Explain why the first ionisation energy of sodium is less than the first ionisation
energy of lithium. ......................................................................................................................
................................................................................................................................................................
................................................................................................................................................................ 2
f) Explain why second ionisation energy of sodium is very much higher than the first
ionisation energy of sodium. ...................................................................................................
................................................................................................................................................................
................................................................................................................................................................ 2
10
5. Using the ionisation energies in the data booklet calculate the energy required for
Al(g)
Al3+ (g) + 3e --
........................ kJ
1
6. Explain why a Si4+ ion is smaller than a P3- ion. ........................................................................
................................................................................................................................................................
................................................................................................................................................................ 2
Total = 20 marks
11
1.6 Properties of Elements, Compounds and Effect of Van der Waal Forces
1.
A
metallic
lattice
B
C
monatomic
covalent
network
D
covalent
molecules
Which box, or boxes, shows the bonding in an element that
a) is a non-conductor with a very high melting point?
........................................
b) is a non-conductor with a low melting point?
........................................
c) is a conductor with a high melting point?
........................................
2.
4
The table below shows the elements in the first three periods of the Periodic
Table. in four classes (A) to (D).
H
He
Li
Be
B
C
N
O
F
Ne
Na
Mg
Al
Si
P
S
Cl
Ar
A
B
C
D
E
a) Use the key shown above to identify the groups of elements (A,B,C,D or E) which
show the following bond types.
i)
Monatomic gases.
.........................
ii) Covalent networks.
.........................
iii) Covalent molecular gases.
.........................
iv) Metallic lattice
........................
v) Covalent molecular solids.
........................
5
b) In which of the groups (A,B,C,D or E) are the following correct
i) delocalised electrons allow the element to conduct when solid.
.........................
ii) both covalent bonds and van der Waals forces are present?
.........................
iii) only covalent bonds are present.
.........................
iv) only van der Waals forces are present.
.........................
12
5
3.
Explain why a metal conducts electricity when solid or molten but an
ionic compound conducts only when molten and not when solid.
.........................................................................................................................................................
.........................................................................................................................................................
.........................................................................................................................................................
.........................................................................................................................................................
2
4. Explain why the melting point increases from top to bottom going down group 7 (the
halogens).
.........................................................................................................................................................
.........................................................................................................................................................
.........................................................................................................................................................
.........................................................................................................................................................
2
5. Two types of carbon are diamond and fullerine.
How does the structure of fullerine differ from that of diamond? ................................
.........................................................................................................................................................
.........................................................................................................................................................
.........................................................................................................................................................
Total = 20 marks
13
2
1.7 Properties of Compounds and Intermolecular Forces
1. a) Which type of bonding exists in
i) silicon dioxide
................................................................................................
ii) sulphur dioxide
................................................................................................
2
b) Use the data booklet to find the boiling points of these two compounds.
silicon dioxide ................. oC
sulphur dioxide ....................... oC
1
c) Explain why the boiling points are so different. ...........................................................
.........................................................................................................................................................
.........................................................................................................................................................
2
2. Copy and complete the table below.
Note:- Under ‘type of bonding’ also mention both intermolecular and intramolecular,
if appropriate.
Element
Type of bonding
Structure
Sodium
Silicon
lattice or network
covalent
Phosphorus
3. Copy and complete the table below:
Note:- Under ‘type of bonding’ also mention both intermolecular and intramolecular,
if appropriate.
Compound
Type of bonding
2
Structure
SiO2
CCl4
covalent intramolecular and
van der Waals forces intermolecular
LiCl
lattice or network
14
2
4.
A
Cl2
D
B
C
HF
E
NaCl
F
C2H5OH
CH3COCH3
SiO2
Which box, or boxes, shows a substance
a) with van der Waals attractions only between molecules?
.................................................
b) with hydrogen bonding between molecules?
................................................
c) with polar attractions, but not hydrogen bonding, between molecules?
d) with a network of oppositely charged ions
5.
A
covalent bonding
...................
................................................
B
5
C
polar covalent bonding
D
E
van der Waals forces
hydrogen bonding
metallic bonding
F
ionic bonding
Which box, or boxes, shows a type of bonding or force of attraction that:a) is responsible for the low melting point of noble gases?
................................
b) exists between molecules?
................................
c) could be considered to be intermediate between ionic and covalent bonding? .............
d) allows electrons a lot of movement?
..............................
e) is important when none of the others are present?
...............................
Total = 20 marks
15
6
1.8 Formula Units and Avogadro’s Constant
1. Calculate the number of atoms present in
a) 4.6 g of sodium
b) 1.25 moles of helium
2
2. Calculate the mass of
a) zinc present in 3.01 x 1022 zinc atoms.
b) sulphur present in 1 x 1020 sulphur atoms.
2
3. A sample of hydrogen sulphide (H2S) weighed 17 g.
How many hydrogen atoms are there in this sample?
1
4. Given 0.5 moles of glucose (C6H12O6), calculate
a) the mass of glucose present.
1
b) the number of oxygen atoms present.
1
5. Given 188 g of magnesium chloride (MgCl2), calculate the number of
a) moles of magnesium chloride present.
1
b) chloride ions present.
1
16
1.9 Excess Calculations
6. Calculate the mass of copper(II) chloride, CuCl2, required to make
200 cm3 of a 0.25 mol l-1 solution of copper(II) chloride.
CuCl2(s) → CuCl2(aq)
3
7. 5g of zinc is reacted with 400 ml of 1 mol l-1 hydrochloric acid.
The equation for the reaction is:-
Zn(s) + 2HCl(aq)
ZnCl2(aq) + H2(g)
a) Show by calculation which reactant is in excess?
b) Calculate the mass of any reactant left.
2
2
c) Calculate the mass of hydrogen gas formed in this reaction.
2
Total = 18 marks
17
1.10 Molar Volume and Calculations Involving Gas Volumes
1.
Calculate the volume composition of the gases present when 50 cm3 of butane is
burned in 500 cm3 of oxygen.
C4H10(g) + 6.5 O2(g)
4CO2(g) + 5H2O(l)
2
2.
Calculate the volume composition of the gases present when 45 cm3 of propene
is burned in 300 cm3 of oxygen assuming that all measurements are made at
a) room temperature.
2
b) 200°C.
3.
Calculate the volume of hydrogen gas formed when 3.25 g of zinc is reacted with an
excess of dilute sulphuric acid. Take the molar volume of a gas, under the
conditions of the experiment, to be 24.0 l mol–1.
Zn(s) + H2SO4(aq)
ZnSO4(aq) + H2(g)
2
18
4.
Calculate the mass of calcium carbonate required to form 2.8 litres of carbon dioxide
when the calcium carbonate is reacted with an excess of dilute hydrochloric acid.
Take the molar volume of a gas, under the conditions of the experiment, to be
22.4 l mol–1.
CaCO3(s) + 2HCl(aq)
CaCl2(aq) + CO2(g) + H2O(l)
2
5. When copper(II) nitrate is heated strongly it decomposes to form copper(II) oxide,
nitrogen dioxide and oxygen.
a) Write a balanced chemical equation for the decomposition of copper(II)
nitrate
....................................................................................................................................................
b) Calculate the volume of each gas present in the mixture formed when
18.4 g of copper(II) nitrate fully decomposes. Take the molar volume of a gas,
under the conditions of the experiment, to be 23.8 litres.
1
2
6. A flask has a capacity of 600 cm3. It was filled with sulphur dioxide and the results
used to calculate the molar volume of sulphur dioxide.
Results:Mass of evacuated (empty) flask
=
Mass of flask filled with SO2
=
412.86 g
414.46g
Use these results to calculate the molar volume of sulphur dioxide.
2
Total = 14marks
19