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Year 13 Chemistry Spring Term Homework Pack
Name: _________________________
Class: _________________________
Teacher: _________________________
Our Spring Term Homework Programme.
Due on [Friday]:
Approximate
Time
Needed
Is there help?
Where can I find it?
Week
#1
Homework 1: [10th Jan]
30 minutes Goo.gl/N1NpEc
Week
#2
Homework 2: [17th Jan]
30 minutes Goo.gl/N1NpEc
Week
#3
Homework 3: [24th Jan]
30 minutes Goo.gl/N1NpEc
Week
#4
Homework 4: [31st Jan]
30 minutes Goo.gl/N1NpEc
Week
#5
Homework 5: [7th Feb]
30 minutes Goo.gl/N1NpEc
Week
#6
Homework 6: [14th Feb]
30 minutes Goo.gl/N1NpEc
Week
#7 -
Half
Term
Homework 7: [28th Feb]
30 minutes Goo.gl/N1NpEc
Week
#8
Homework 8: [6th Mar]
30 minutes Goo.gl/N1NpEc
Week
#9
Homework 9: [13th Mar]
30 minutes Goo.gl/N1NpEc
Week
#10
Homework 10: [20th Mar]
30 minutes Goo.gl/N1NpEc
Week
# 11
Homework 11: [27th Mar]
30 minutes Goo.gl/N1NpEc
Week
#12
Homework 12: [4th Apr]
30 minutes Goo.gl/N1NpEc
2
Homework #1. DUE: [10th Jan]
[Title]
1. Citric acid has a Ka value of 3.2 x 10-7, find the pKa.
2. The solution of citric acid is 0.1 M solution.
a) Write an expression for Ka.
b) What value will the [citric acid] be roughly equal to?
c) Put your numbers into the equation from a)
d) Solve to find [H+]2
e) Find [H+]
3. Propanoic acid has a Ka value of 1.3 x 10-5 (2 sf), find its pKa and the pH value of a 0.01
M solution.
4. a) Ascorbic acid (Mr = 176.12 g/mol) is an organic acid used in the food industry, it has a
pKa value of 4.1. Does this make it a strong or a weak acid?
b) If an ascorbic solution were prepared using 2.229 g in 1 dm3, show its molarity would
be 1.2656 x 10-2 M.
c) Write an expression to link the concentration of acid and the Ka value to the proton
concentration.
d) Put the values for Ka and [acid] in and solve the equation to find [H+]2, [H+] and hence
pH.
3
5. a) Prussic acid is highly toxic and has a pKa value of 9.2. Is the acidity the killer or the
chemistry it performs? Find the Ka value to prove your point.
b) If 3.456 x 10-3 g are dissolved in 2 dm3 of water, what is the molarity?
c) Find the [H+]2, [H+] and pH values for this solution.
6. Hydrofluoric acid is from the same group of elements as hydrochloric (pKa = -7),
hydrobromic (pKa = -9) and hydroiodic (pKa = -10) acid. It has a Ka value of 6.76 x 10-4.
Comment on this pattern and suggest a reason for any discrepancy.
7. a) What would the pH be of a 0.001 M solution of HF and a 0.001M HCl be?
b) How much stronger is the HCl solution?
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Homework #2. DUE: [17th Jan]
[Title]
4.3 Exercise 3 - Buffer solutions
1. a) What is meant by the term "buffer solution"?
b) Calculate the pH of a buffer solution which contains the weak monoprotic acid, propanoic
acid (CH3CH2COOH), in concentration 0.1 moldm-3 and sodium propanoate in concentration
0.05 moldm-3. Ka of propanoic acid is 1.26 x 10-5 moldm-3.
c) Give equations to show how the above solution fulfills its buffer function.
d) Calculate the pH of the solution after 0.01 moles of NaOH are added to 500 cm3 of the
solution.
e) Calculate the pH of the solution after 0.01 moles of HCl are added to 500 cm3 of the
solution.
f) Calculate the pH after 0.01 moles of NaOH is added to 500 cm3 of water.
g) Comment on your answers to (d) and (f).
2. a) Calculate the pH of 0.12 moldm-3 ethanoic acid (Ka = 1.7 x 10-5 moldm-3).
b) Calculate the mass of sodium ethanoate (CH3COONa) which must be added to 500 cm3 this
solution to give a buffer solution of pH = 4.60.
c) Calculate the pH of this solution after 0.01 moles of HCl are added.
6
d) Calculate the pH of this solution after 0.01 moles of NaOH are added.
3. Calculate the pH of a buffer which is 0.2 moldm-3 with respect to ammonium sulphate and 0.1 moldm-3 with respect to ammonia. (Ka of NH4
+ = 5.6 x 10-10 moldm-3)
4. Methanoic acid, HCOOH, has a Ka value of 1.58 x 10-4 moldm-3. What ratio of methanoic acid and sodium methanoate would give a buffer of pH = 4?
5. a) Calculate the pH of a buffer solution which is 0.1 moldm-3 with respect to HCN (Ka = 4.9 x 10-10 moldm-3) and 0.8 moldm-3 with respect to sodium cyanide.
b) Calculate the pH after 0.05 moles of HCl are added to 1 dm3 of this buffer.
c) Calculate the pH after 0.05 moles of NaOH are added to 1 dm3 of this buffer.
d) Calculate the pH after 0.2 moles of NaOH are added to 1 dm3 of this buffer.
e) Comment on your answer to (d).
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Homework #3. DUE: [24th Jan]
[Title]
4.3 Exercise 4 - Titrations and indicators
1. 20 cm3 of methanoic acid (Ka = 1.8 x 10-4 moldm-3) of concentration 0.10 moldm-3 is titrated
against sodium hydroxide of concentration 0.05 moldm-3.
a) Calculate the pH of the solution:
i) initially
ii) after 10 cm3 of the alkali has been added
iii) after 20 cm3 of the alkali has been added
iv) after 30 cm3 of the alkali has been added
v) after 50 cm3 of the alkali has been added
b) Sketch a pH titration curve to show this reaction
c) Explain why the pH at the end-point is greater than 7.
2. Calculate the pH after the following solutions are mixed together:
a) 15 cm3 of 0.1 moldm-3 HCl and 10 cm3 of 0.1 moldm-3 NaOH
b) 10 cm3 0.1 moldm-3 HCl and 15 cm3 of 0.1 moldm-3 NaOH
3. Sketch pH curves for the following titrations:
a) 20 cm3 0.10 moldm-3 NH3 against 0.1 moldm-3 HCl
b) 20 cm3 0.10 moldm-3 NaOH against 0.2 moldm-3 HCl
c) 20 cm3 0.10 moldm-3 CH3COOH against 0.06 moldm-3 NaOH
d) 20 cm3 0.10 moldm-3 CH3COOH against 0.15 moldm-3 NH3
4. Given the following pKIn values:
Indicator pKIn
Methyl red 5.1
Phenolphthalein 9.3
State, with a reason, which of the indicators would be suitable for each of the titrations in question 3.
8
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9
Homework #4. DUE: [31st Jan]
[Title]
4.9 Exercise 1 - addition polymers
1. Draw two repeating units of the polymer produced by the following alkenes:
a) propene b) but-1-ene c) but-2-ene d) phenylethene e) tetrafluoroethene
2. Name the following polymers and draw the monomer from which the polymer is made:
a)
C C CC
n
CH3
CH3 CH3 CH3 CH3
CH3CH3 CH3
b)
C C CC
n
CH3 CH3
H HH H
ClCl
c)
C C CC
n
H
ClCl HH
H ClCl
10
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Homework #5. DUE: [7th Feb]
[Title]
4.9 Exercise 2 – condensation polymers
1. Predict the products of the following reactions:
a) benzene-1,4-dicarboxylic acid with 1,2-diaminoethane
b) hexane-1,6-dioyl chloride with propan-1,2-diol
c) ethanedioic acid with ethan-1,2-diol
2. From what monomers can the following condensation polymers be made:
a) terylene
b) nylon 66
c)
C
O
O C C
CH
H H
H
H
H
C
O
O
n
H
OH
12
d)
N
H
C
O
C
O
N
H
C C
n
H H
H H
HCl
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13
Homework #6. DUE: [14th Feb]
[Title]
4.8 EXERCISE 1 – amino acids
1. a) Draw the structure of 2-aminobutanoic acid
b) Draw the two optical isomers of 2-aminobutanoic acid
c) Write equations to show the reaction of 2-aminobutanoic acid with
i) hydrochloric acid
ii) sodium hydroxide
d) Draw the structure of the dipeptide formed by the condensation of
i) two molecules of 2-aminobutanoic acid
ii) three molecules of 2-aminobutanoic acid
iii) four molecules of 2-aminobutanoic acid
2. a) Describe the shape of the protein molecule and explain why it has this shape.
b) Draw the organic products formed when the following protein is heated with concentrated
hydrochloric acid:
N
H
C
H
O C
O
H N
H
C
H
N H
H
C
O
N
H
C
H
C
O
C
H
C
OH CH2
OH
CH3 CH2
CH3
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15
Homework #7. DUE: [28th Feb]
[Title]
5.3 EXERCISE 1 – OXIDATION AND REDUCTION
1. Deduce the oxidation numbers of the following atoms:
a) Mn in MnO4-
b) O in H2O2
c) Cr in Cr2O72-
d) Cr in CrO42-
e) V in VO2+
f) V in VO2+
2. Derive balanced half-equations for the following reduction processes:
a) MnO4- to Mn2+
b) Cr2O72- to Cr3+
c) Zn2+ to Zn
d) Fe3+ to Fe2+
e) H2O2 to H2O
3. Derive balanced half equations for the following oxidation processes:
a) Zn to Zn2+
b) Fe2+ to Fe3+
c) H2O2 to O2
16
d) SO32- to SO4
2-
4. Write balanced equations for the following redox reactions:
a) MnO4- with Fe2+
b) Cr2O72- with H2O2
c) VO2+ to V2+ with Zn
d) VO2+ to VO2+ with SO3
2-
5. Write half-equations to show the following processes in excess alkali. State in each case whether
oxidation or reduction is taking place.
a) O2 to OH-
b) Cr3+ to CrO42-
c) H2O2 to OH-
d) MnO4- to MnO2
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18
Homework #8. DUE: [6th Mar]
[Title]
5.3 EXERCISE 2 - electrochemical cells
1. Draw the conventional representation of the electrochemical cells to show how you would use
the following reactions to make electricity (they are all spontaneous). In each case indicate the
polarity of the electrodes.
a) Fe(s) + Cu2+(aq) → Fe2+(aq) + Cu(s)
b) 2Fe3+(aq) + 2I-(aq) → 2Fe2+(aq) + I2(aq)
c) Zn(s) + 2H+(aq) → Zn2+(aq) + H2(g)
d) 2H2(g) + O2(g) → 2H2O(l)
2. Deduce the chemical reaction taking place in the following cells, given the following data:
Half-reaction E/V
Zn2+(aq) + 2e → Zn(s) -0.76
Fe2+(aq) + 2e → Fe(s) -0.44
Fe3+(aq) + e → Fe2+(aq) +0.77
Ag+(aq) + e → Ag(s) +0.80
Cl2(g) + 2e → 2Cl-(aq) +1.36
a)
Zn Zn2+ Fe3+, Fe2+ Pt
b)
Fe Fe2+ Fe3+, Fe2+ Pt
19
c)
Ag Ag+ Cl2, Cl- Pt
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Homework #9. DUE: [13th Mar]
[Title]
5.4 EXERCISE 1 – Transition Metals
1. Give the electronic configuration of the following atoms:
a) V
b) Cr
c) Co
d) Cu
e) Zn
2. Give the electronic configuration of the following ions:
a) Co2+
b) Cu+
c) V3+
d) Cr3+
e) Fe3+
3. a) Explain why Sc and Zn are not classified as transition metals
b) Explain how transition metals can form complex ions
d) Explain why complex ions are often coloured
e) Explain why Cu+ is not coloured
4. Explain how the colour of solutions containing transition metals can be used to determine their
concentration.
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Homework #10. DUE: [20th Mar]
[Title]
Lesson 12 - 5.4 EXERCISE 3 – Variable oxidation states and catalysis
1. Describe what happens when the following species are acidified and then treated with zinc and
account for all your observations:
a) ammonium vanadate (V)
b) potassium chromate (VI)
2. Describe what happens when the following species are treated with sodium hydroxide and hydrogen
peroxide and account for all your observations:
a) cobalt (II) chloride
b) chromium (III) chloride
3. Describe what happens when cobalt chloride is treated with concentrated ammonia solution and
then left to stand in air. Account for all your observations.
4. Describe two ways in which the concentration of Fe2+ in a sample could be determined by titration.
In each case write an equation for the reaction occurring during the titration.
5. a) Write an equation for a reaction catalysed by the following substances and explain why they
are important:
i) V2O5
ii) Fe
iii) Ni
iv) Rh
24
b) Give two examples of catalyst poisoning
c) Explain why a ceramic support in used for Rh in example (i) (iv)
d) Explain why Fe is a better catalyst than W and Ag.
6. Explain how the following reaction can be catalysed by both Fe2+ and Fe3+ ions:
S2O82-(aq) + 2I-(aq) → 2SO4
2-(aq) + I2(aq)
For each ion, write two equations to show the catalysed pathway and explain why both are faster
than the uncatalysed reaction.
7. a) Write an equation for the reaction which occurs during the titration between ethanedioic
acid (H2C2O4) and KMnO4.
b) Explain why the reaction is slow initially but quite fast close to the end-point.
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Homework #11. DUE: [27th Mar]
[Title]
1. When CuCl is dissolved in an excess of concentrated hydrochloric acid, a colourless solution
containing the complex ion, [CuCl2]–, is formed. When hydrogen peroxide, H2O2, is added to this
acidified solution, a green solution containing a copper complex ion, X, and water are formed.
On the addition of a large excess of water, a blue solution containing the copper complex ion, Y
is formed.
(a) Give the oxidation state of copper in [CuCl2]–, give the electronic configuration of copper
in this species and deduce why it is colourless.
Oxidation state............................................................................................................
Electronic configuration.............................................................................................
Deduction.................................................................................................................... (3)
(b) Give the formula and shape of the copper complex ion X.
Formula.......................................................................................................................
Shape........................................................................................................................... (2)
(c) State the role of hydrogen peroxide in the formation of X.
..................................................................................................................................... (1)
(d) Construct a half-equation for the formation of water, as the only product, from hydrogen
peroxide in acid solution.
..................................................................................................................................... (I)
(e) Write an equation for the formation of Y from X and identify the role of water in this
reaction.
Equation......................................................................................................................
Role of water............................................................................................................... (2)
(Total 9 marks)
27
2. (a) Define the terms Lewis acid and Brønsted Lowry acid
Lewis acid...................................................................................................................
Brønsted-Lowry acid.................................................................................................. (2)
(b) (i) Write an equation to show what happens when anhydrous aluminium chloride is
added to an excess of water.
.........................................................................................................................
(ii) Write an equation to show that the aluminium species formed in part (i) can behave
as a Brønsted-Lowry acid.
.........................................................................................................................
(iii) Construct an equation to show aluminium chloride acting as a Lewis acid in its
reaction with concentrated hydrochloric acid.
......................................................................................................................... (3)
(c) Describe what you would see, and give the formulae of the iron-containing or chromium-
containing products formed, when
(i) aqueous iron(III) chloride is treated with an excess of solid sodium carbonate:
Observation(s)..................................................................................................
...........................................................................................................................
Formula of iron-containing product.................................................................
(ii) aqueous chromium(III) sulphate is added to an excess of aqueous sodium hydroxide.
Observation(s)....................................................................................................
............................................................................................................................
Formula of chromium-containing product......................................................... (6)
(Total 11 marks)
28
Homework #12. DUE: [4th Apr]
[Title]
3. When a solution of [Ti(H2O)4Cl2]+ ion is diluted with water, a substitution reaction occurs
and the pink [Ti(H2O)6]3+
ion is formed.
(i) Explain what is meant by the term substitution reaction.
............................................................................................................................
............................................................................................................................
(ii) Construct an equation for this reaction.
............................................................................................................................
............................................................................................................................
(iii) What change to the titanium ion is responsible for the colour change in the reaction?
............................................................................................................................ (3)
(Total 3 marks)
4. Study the passage below
A crystalline solid A dissolves in water to give a solution containing the metal complex
ion B.
Addition of aqueous silver nitrate to this solution gives a white precipitate of C which dissolves
when an excess of dilute aqueous ammonia is added to form a solution containing the metal
complex ion D.
The solution of A becomes a blue solution containing metal complex ion E when an excess of
concentrated hydrochloric acid is added.
When concentrated aqueous ammonia is added dropwise to a solution of A, a blue-green
precipitate F forms. This then dissolves when an excess of ammonia is added to form a pale
brown solution containing the metal complex ion G. This pale brown solution becomes dark
brown on standing in air and a solution containing the metal complex ion H is formed.
Identify by formula, each of the species lettered B – H and finally the solid A.
Formula of complex ion B.....................................................................................................
Formula of precipitate C.......................................................................................................
Formula of complex ion D.....................................................................................................
Formula of complex ion E.....................................................................................................
Formula of precipitate F.......................................................................................................
29
Formula of complex ion G.....................................................................................................
Formula of complex ion H.....................................................................................................
Formula of starting solid A................................................................................................... (Total 8 marks)
5. (a) State what is meant by the term co-ordinate bond.
...............................................................................................................................
............................................................................................................................... (2)
(b) Define the terms Brønsted–Lowry acid and Lewis acid.
Brønsted–Lowry acid ............................................................................................
Lewis acid ............................................................................................................. (2)
(c) State what is meant by the term bidentate ligand.
..............................................................................................................................
.............................................................................................................................. (2)
(d) State how the co-ordination number of cobalt(II) ions in aqueous solution changes when an
excess of chloride ions is added. Give a reason for the change.
Change in co-ordination number ...........................................................................
Reason for change .................................................................................................
............................................................................................................................... (2)
(e) Suggest why the enthalpy change for the following reaction is close to zero.
[Co(NH3)6]2+
+ 3NH2CH2CH2NH2 → [Co(NH2CH2CH2NH2)3]2+
+ 6NH3
...............................................................................................................................
............................................................................................................................... (2)
(f) Deduce the formula of the compound formed when ethane-1,2-diamine is treated with an
excess of hydrochloric acid.
............................................................................................................................... (1)
(Total 11 marks)
