Chemistry

IEB

Practice Questions

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Instructions

Individual, exam-style questions The questions contained in this booklet match the style of questions that are typically asked

in exams. This booklet is not however, a practice exam. Elevate’s research with top students

identified that top students do more practice questions than anyone else. They begin the

process of testing their knowledge early in the year.

Therefore, we have provided exam-format questions that are sorted by topic so that you can

answer them as you learn the information, rather than waiting until the very end of the year to

complete exams.

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Multiple Choice questions

1. Nickel rods are placed separately into different test tubes each containing a different solution. In which solution is nickel oxidised and a metal displaced from solution?

A) MgCl2 (aq) B) Zn(NO3)2 (aq) C) NaNO3 (aq) D) CuSO4(aq)

2. In the following redox reaction, electrons are transferred from Ca + Zn2+ → Ca2+ + Zn A) Ca2+ to Zn B) Ca to Ca2+ C) Ca to Zn D) Ca to Zn2+

3. Why is the boiling point of iodine monochloride, ICl, nearly 400 higher than that of

bromine, Br2, although the two substances have almost the same molecular mass? A. ICl is an unsymmetrical molecule B. ICl has a giant covalent structure C. The I - Cl bond is stronger than the Br – Br bond D. ICl is a polar molecule

4. A certain standard electrochemical cell may be written as:

Pt, I−/ I2 // Br2 /Br -, Pt Which of the species will be oxidized in the cell reaction? A) Pt B) I− C) I2 D) Br2 E) Br−

5. The petrol additive tetraethyl-lead(IV), Pb(C2H5)4 has been added to petrol since 1920. The global phasing out of this additive is scheduled to be completed this year. When it is completely burnt in air, lead(II)oxide (PbO), carbon dioxide, and water are formed.

How many moles of oxygen are required to burn one mole of Pb(C2H5)4? The unbalanced equation for this reaction is given below.

Pb(C2H5)4(l) + O2(g) → PbO(s) + CO2(g) + H2O(l) A. 9,5 B. 11 C. 13,5 D. 27

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6. What is the IUPAC name of the following compound?

H H H

H C C C C H

CH3 H CH3

A. 2,4-dimethylbut-1-ene B. 1,3-dimethylbut-3-ene C. 1,3-methylbut-1-ene D. 2-methylpent-1-ene

7. Which of the following is an unsaturated hydrocarbon?

A CH3CH2CH2OH B CH2CHCH3

C CH3CH2(CH3)CH2CH3

D CH3COOCH3

8. In the reaction:

2I− + F2 → I2 + 2F−

A) iodine is oxidised. B) fluorine acts as a reducing agent. C) the stronger reducing agent is produced. D) fluoride is oxidised. E) fluorine is reduced.

9. In the diagram, curve X was obtained by observing the decomposition of 100 cm3 of 1,0 mol.dm-3 hydrogen peroxide, H2O2, catalysed by manganese (IV) oxide. The products of this reaction are water and oxygen.

Which alteration of the original experimental conditions would produce curve Y?

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A. Adding water B. Adding 0,1 mol.dm-3 hydrogen peroxide C. Using less manganese (IV) oxide D. Lowering the temperature

10. The Eo value of the Ni2+/Ni(s) electrode is usually determined using a standard H+/H2; Pt

electrode as reference electrode. The equation for the half-reaction which occurs at the anode of this cell is:

A) H2(g) → 2H+ + 2e− B) 2H+ + 2e− → H2(g) C) Ni (s) → Ni2+ + 2e−

D) Ni2+ + 2e− → Ni(s)

11. The following two changes were carried out separately on each of the systems listed below:

(i) Pressure was reduced at constant temperature; (ii) Temperature was increased at constant pressure

Which system would give an increase in the proportion of products in both of these changes?

A. H2(g) + I2(g) ⇌ 2HI(g) ΔH = + 53 kJ.mol-1 B. 4NH3(g) + 5O2(g) ⇌ 4NO(g) + 6H2O(g) ΔH = - 950 kJ.mol-1 C. N2(g) + 3H2(g) ⇌ 2NH3(g) ΔH = - 92 kJ.mol-1 D. N2O4(g) ⇌ 2NO2(g) ΔH = + 57 kJ.mol-1

12. According to the redox table, which one of the following would NOT react together

spontaneously under standard conditions? A) Co and Cu2+ B) Ni and I2 C) Zn and Al3+ D) H2O and Mg

13. Which of the following will reduce Ag+ to Ag but not Ni2+ to Ni A) H2S B) Zn

C) Mn D) Na

14. When 0,20 mol of hydrogen gas and 0,15 mol of iodine gas are heated to

723 K an equilibrium is established. The equilibrium mixture is found to contain 0,26 mol of hydrogen iodide.

The reaction for the equation is as follows:

H2(g) + I2(g) ⇌ 2HI(g)

What is the correct expression for the equilibrium constant Kc?

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A. "$%,"'

%,"$%,()

B. ("+%,"')-

%,"+%,()

C. (%,"')-

%,%.+%,%"

D. (%,"')-

%,(/+%,(/

15. In the manufacture of aluminium by electrolysis, fluorine, hydrogen fluoride and

carbon monoxide may be evolved as undesirable by-products. Which of the following are the sources of these gases?

Source of fluorine and hydrogen fluoride

Source of carbon monoxide

A the bauxite in the electrolyte the anode B the bauxite in the electrolyte the cryolite in the electrolyte C the cryolite in the electrolyte the anode D the cryolite in the electrolyte the cathode lining

16. In the electrolysis of aqueous silver nitrate, how many electrons are required to

deposit 1,08 g of silver at the cathode?

A. 3,01 x 1021 B. 6,02 x 1021 C. 1,20 x 1022 D. 6,02 x 1025

17. ) Three different types of organic reactions are described below :

I alkane haloalkane II carboxylic acid + alcohol III alkene alcohol Which option below best names the reaction types?

I II III A Substitution Esterification addition

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B Addition Oxidation elimination C Substitution Hydration addtition D Halogenations Esterification elimination

18. ) A piece of tin metal is placed in each of the following four test tubes containing an

aqueous solution as indicated below. In which test tube (A – D) will a metal deposit be seen on the surface of the tin metal?

Answer: B

19. The reaction represented by the equation below takes place in the presence of a catalyst.

C13H28(l) → C2H4(g) + C3H6(g) + C8H18(l)

This reaction is an example of

A. cracking B. addition C. substitution D. oxidation

20. Which of the following represents the organic compound 1,2,3-tribromo-3- fluoropropane?

A.

B.

H F H H C C C H Br Br Br F H Br H C C C Br H H Br

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C.

D.

21. A certain standard electrochemical cell may be written as: Mg|Mg2+

|| I2|I−, Pt Which of the species will be reduced? A) Pt B) Mg2+ C) I2 D) I− E) Mg2+

22. The Eθ value for the Zn/Zn2+ electrode is determined using the standard H+/H2, Pt-electrode as reference electrode. The equation for the half-reaction that occurs at the ANODE of the cell is...

A) 2H+ + 2e- → H2 B) Zn2+ + 2e- → Zn C) Zn → Zn2+ + 2e- D) H2 → 2H+ + 2e-

23. Photochromic glass contains silver ions and copper ions. A simplified version of a redox equilibrium is shown below. In bright sunlight the high energy u.v. light causes silver atoms to form and the glass darkens. When the intensity of the light is reduced the reaction is reversed and the glass lightens.

Cu+(s) + Ag+(s) Cu2+(s) + Ag(s) clear glass dark glass

When the photochromic glass darkens

A) the Ag+ ion is acting as an electron donor.

B) the Cu+ ion is acting as a reducing agent.

C) the Ag+ ion is oxidised.

D) the Cu+ ion is reduced.

F H H H C C C H Br Br Br H H F H C C C Br H Br Br

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24. The hypothetical half reactions for a certain electrochemical cell are:

X2+ + 2e- ⇌ X E0 = + 0.80 V

Y+ + 1e- ⇌ Y E0 = - 0.76 V

Which species acts as the reducing agent in this cell?

A) X2+ B) X C) Y+ D) Y

25. Which one of the following will oxidise Ni to Ni2+, but will not oxidise Ag to Ag+ ?

A) Na+ B) I2 C) Cl2

D) Zn

26. The Eθ value for the Cu2+ /Cu electrode is determined using the standard H+/H2, Pt-electrode as reference electrode. The equation for the half-reaction that occurs at the CATHODE of the cell is...

A) 2H+ + 2e- → H2 B) Cu2+ + 2e- → Cu C) Cu → Cu2+ + 2e- D) H2 → 2H+ + 2e-

27. Conductor Y is permanently fixed to an aluminium plate are shown in the diagram below. The plate is covered by a piece of filter paper soaked in a KNO3 solution. Point X can be brought into contact with any of the clean metal pieces arranged on the filter paper covering the aluminium plate.

The voltmeter will give the highest reading when X is in contact with which metal piece?

A) Zn B) Mg C) Ag

D) Fe

28. An electrochemical cell consists of a Sn2+/Sn half-cell connected to an “unknown half-

cell” under standard conditions. The voltage of the cell is 0,14V, with the tin terminal connected to the positive of the voltmeter. The “unknown half cell’ is:

A) Co2+/Co B) 2H+,H2/Pt

X

Y

Aluminiumplate

Zn Mg Ag Fe

V

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C) [S+2H+],H2S/Pt D) Cd2+/Cd

29. The hypothetical half reactions for a certain electrochemical cell are:

X2+ + 2e- ⇌ X E0 = + 0.80 V

Y+ + 1e- ⇌ Y E0 = - 0.76 V

Which species acts as the reducing agent in this cell?

A) X2+ B) X C) Y+ D) Y

Multiple Choice Solutions

1. D 2. D 3. D 4. B 5. C 6. D 7. B 8. E 9. B 10. C 11. D 12. C 13. A 14. C 15. C 16. B 17. A 18. B 19. A 20. C 21. C 22. C 23. B 24. D 25. B 26. B 27. C 28. A 29. D

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Long Questions QUESTION 1: Draw the structural formula for the compound : 2,3-bromochloropropan-2-ol QUESTION 2: Write the IUPAC name for the following compound :

CH3CH2CHBrCH(C2H5)CH2CH3 QUESTION 3: The following sketch is a representation of an electrochemical cell under standard conditions. A suitable bulb in the external circuit glows brightly.

a) Write down the half reaction equation for the reaction at the anode.

b) Determine and write down the overall balanced ionic equation for this reaction.

c) Calculate the EMF of the cell.

d) In which direction do: i) positive ions flow in the salt bridge?

ii) negative ions flow in the salt bridge?

Ag(s)Al(s)

SolutionofAluminiumnitrate

Solutionofsilvernitrate

Cottonwoolsaltbridge

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e) Explain the effect on the voltage delivered by the cell if NaCl solution is added to the silver nitrate causing a precipitate.

QUESTION 4: Use the data below to answer the questions that follow:

Reduction Reactions at 298 K E /V

Ag+(aq) + e– Ag(s) +0.08

AgF(s) + e– Ag(s) + F–(aq) +0.78

AgCl(s) + e– Ag(s) + Cl–(aq) +0.22

AgBr(s) + e– Ag(s) + Br–(aq) +0.07

H+(aq) + e– ½ H2(g) 0.00

D+ (aq) + e– ½ D2(g) –0.004

AgI(s) + e– Ag(s) + I–(aq) –0.15

The symbol D denotes deuterium, which is heavy hydrogen, H.

(a) By considering electron transfer, state what is meant by the term oxidising agent.

(b) State which of the two ions, H+(aq) or D+(aq), is the more powerful oxidising agent. Write an equation for the spontaneous reaction which

occurs when a mixture of aqueous H+ ions and D+ ions are in contact with a mixture of hydrogen and deuterium gas. (4)

(c) Silver does not usually react with dilute solutions of strong acids to liberate hydrogen.

(i)State why this is so. (ii) Suggest a hydrogen halide which might react with silver to liberate hydrogen in aqueous solution.

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QUESTION 5: The figure below shows how blocks of magnesium are connected to an iron pipeline buried in wet soil containing electrolytes.

a) In which direction will electrons move in wire P? (Magnesium to iron pipe OR iron pipe to magnesium) b) Which metal acts as the anode? c) How does the mass of the magnesium block change over a period of time what is the purpose of this process?

QUESTION 6:

Analyze the following reactions • Identify if the reaction is a redox reaction. • If so, then write the oxidation number for each element. • If so, state which species are being oxidized and reduced?

a) 𝐴𝑔𝑁𝑂/(45) + 𝑁𝑎𝐶𝑙(45) → 𝐴𝑔𝐶𝑙(;) + 𝑁𝑎𝑁𝑂/(45)

b) 𝑍𝑛(;) + 𝐶𝑢𝑆𝑂@(45) → 𝑍𝑛𝑆𝑂@(45) + 𝐶𝑢(;) c) 𝑀𝑔(;) + 2𝐻𝐶𝑙(45) → 𝑀𝑔𝐶𝑙"(45) + 𝐻"(D) d) 𝐻"𝑆𝑂@(45) + 2𝑁𝑎𝑂𝐻(45) → 𝑁𝑎"𝑆𝑂@(45) + 2𝐻"𝑂(45)

QUESTION 7: Refer to compounds A to E below, along with their boiling points:

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All of the compounds, A to E, belong to one of two homologous series.

1. Name the two homologous series represented from A to E, and using only the letters, list the compounds belonging in each series.

2. Consider compound D for the following questions. a. Name compound D b. Give the full structural formula and name of a functional isomer of

compound D.

3. Consider compounds B and E for the following questions.

a. Explain the difference in boiling points of compounds A and E b. What is the IUPAC name for compound E? c. Give the full structural formula of a positional isomer of

compound B.

4. Compounds A and D combine with each other to form an ester with a distinctive scent.

a. Describe the conditions required for the formation of this ester. b. Write down the structural formula AND the IUPAC name for the ester formed between A and D 5. Compound A is a liquid at room temperature. A similar one-carbon compound,

methane, is a gas at room temperature.

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Explain why these similar compounds are found in different phases at room temperature.

QUESTION 8: a) Calculate the E˚ of the cell for the cell reaction in which Cu2+ reacts with zinc. b) How will the E value change if one decreases the concentration of the electrolyte in the anode of the cell mentioned in a) c)Calculate the E˚ for the cell in which the following overall reaction occurs:

𝐶𝑢(;) + 𝐹𝑒/G(45) → 𝐶𝑢"G(45) + 𝐹𝑒"G(45) d) How will the E value change if one increases the concentration of the electrolyte in the cathode of the cell mentioned in c)? e) Calculate the E˚ for the cell involving silver metal and its ions as one of the electrodes and magnesium metal and its ions as the other and write the overall cell reaction.

f) How would the E value change if one adds hydrochloric acid into the silver half- cell of e)? QUESTION 9:

a) Draw a diagram of a cell which has the cell notation: Zn / Zn2+ // Ag+ / Ag

b) Which is the positive terminal of the cell?

c) Calculate the EMF of the cell. d) In which direction do ions flow in the salt bridge?

e) Write an equation for the reaction that takes place in the beaker: (i) containing Ag+(aq)

(ii) containing Cu2+(aq)

e) Write an overall equation for the cell-reaction by combining the two half-cell reactions that you have written in e.

QUESTION 10:

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Consider the burning of methanol in oxygen. 1.What type of reaction is this? 2. Write the balanced chemical equation to represent this reaction. 3.If there is not enough oxygen present this reaction will be incomplete. What other products are likely to form? 4.Draw the structural formulae for formaldehyde and for formic acid. 5. Give the correct IUPAC name for formaldehyde. 6.Consider the reaction of methanol with ethanoic acid. 7. Write the balanced chemical equation to represent this reaction. 8. Draw the structural formula of the ester produced in this reaction. 9. Name the ester produced in this reaction. 10. Name an acid isomer of this ester. QUESTION 11:

CH3CHCH2 undergoes addition polymerisation.

1. Name the polymer formed from the polymerisation of E.

2. Draw the structure of the repeat unit that makes up this polymer.

This polymer is a strong, dense, recyclable thermoplastic which can be used to make heavy duty plastic wrap, carpets and ropes.

3.Would you expect this polymer to have permanent cross-links between its chains? Explain briefly.

4. Predict whether or not you would expect this polymer to have branched or unbranched chains. Explain.

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Solutions QUESTION 1: H Br Cl H - C – C – C - H H OH H QUESTION 2: . 3-bromo-4-ethylhexane QUESTION 3: a) Al → Al3+ + 3e multiplying Ag ½ equation by 2 b) multiplying Ag ½ equation by 2 Al + 3Ag+ → Al3+ + 3Ag Al + 3Ag+ → Al3+ + 3Ag c) E0 = Eo

cathode - Eoanode

= 0,8 – (-1,66) = 2,46V

d) i (Anode to cathode) or (Al to Ag) ii Other way to above answer

f) Decrease Voltage as concentration of Ag+ decreases QUESTION 4: a) It aids the oxidation reaction by accepting electrons. b) H+ is more easily reduced (or more powerful OAgent) H+ + ½ D2 → ½ H2 + D+ ci) Must discuss relative Eo values of Ag+/Ag with that of H+/H2 to get the mark. For example, for Ag to react it must be oxidized but relative to H+ it as a + Eo cell potential therefore not

likely to be oxidized or Ag+(aq) is a stronger oxidising agent than H+(aq) cii) AgI QUESTION 5: a) Mg to pipe (Fe) b) Mg c) Decreases-To prevent corrosion of pipe (Fe)

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QUESTION 6:

a. Not redox (no electron transfer) oxidation numbers unchanged

b. Redox Zn oxidised and Cu2+ reduced

c. Redox Mg oxidised and H+1 reduced

d. Not redox

QUESTION 7:

1. alcohols : A,B,C.E Carboxylic acids : D allocation 2 a. ethanoic acid b. functional isomer of C2H4O2 : methyl methanoate O H H – C – O – C – H H

3. a. bp (A) << bp (E) because more sites/position for hydrogen bonding (strongest IMF) between molecules of E therefore more energy needed to separate molecules of E

b. 1,2,3-propantriol c. positional isomer of C3H8O3 : eg. 1,1,2-propantriol OR 1,2,2-propantriol OH OH H OH OH H H – C – C – C – H H – C – C – C - H OH H H H OH H

4. a. heat and conc sulphuric acid b. ester formed : methylethanoate H O H H – C – C – O – C – H H H 5. At RT methanol is liquid while methane is gas – because IMF between CH4 non-polar molecules are weak London (VDW) forces while IMF between CH3OH polar molecules are strong H bonds – therefore at RT, insufficient energy to separate CH3OH molecules.

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QUESTION 8:

a. 1.1 V

b. E0 will increase [ according to LCP : when [Zn2+] is decreased - reverse, oxidation ½ reaction is favoured which re-enforces the complete redox reaction]

c. 0.43 V

d. E0 will increase (when [Fe3+] is increased – fwd reduction ½ reaction is favoured which re-enforces the complete redox reaction ]

e. 3.17 V 2Ag+(aq) + Mg(s) 2Ag(s) + Mg2+

(aq)

f. If HCl(aq) added then reaction between Cl- ions and Ag+ ions forms INSOLUBLE AgCl. The resultant drop in [Ag+] causes DROP in E0 value

QUESTION 9: a) Show: Salt Bridge, terminals, correct solutions, correct terminals. b) Ag or Cathode c) E0

cell = E0cath – E0

anode = 0,8 – (-0,76) = 1,56V d) Positive from anode (Zn) to cathode (Ag) Negative from cathode to anode ei) Ag+ + e → Ag eii) Zn → Zn2+ + 2e

AgNO3(aq)

Zn Ag

ZnSO4(aq)

Saltbridge

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f) Zn + 2Ag+ → Zn2+ + 2Ag QUESTION 10: 1. Combustion 2 2CH 3OH + 3O 2 à 2CO 2 + 4H 2 O

3. Carbon monoxide and carbon (or symbols). 4. H I H - C = 0 formaldehyde 0 II H – C – 0H formic acid 5. Methanol 6. CH 3 0H + CH 3C00H à CH 3C00CH 3 + H 2 0

7. H O H I II I H – C – O – C – C – H I I H H 8. Methyl ethanoate

9. Propanoic acid. 10. Identical. QUESTION 11: 1.Polypropylene (or polypropene) 2.

3. No since it is a thermoplastic it would have van der Waal’s forces between its chains. Thermosets have permanent cross-links (covalent bonds). (OR it is recyclable and permanent cross-links prevent recycling)

4. Unbranched. It is dense molecules must be close packed which is not possible with

branches.

CH3H ⏐ ⏐ – C – C –