Syllabus Edition

First teaching 2023

First exams 2025

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The Periodic Table: Classification of Elements (HL IB Chemistry)

Exam Questions

6 hours98 questions
1a1 mark

Define the term first ionisation energy and state what is meant by the term periodicity.

1b1 mark

Distinguish between the terms group and period.

1c1 mark

State the property that determines the order in which elements are arranged in the periodic table.

1d2 marks
State the relationship between the electron arrangement of an element and its group and period in the periodic table.

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2a2 marks

Explain the following statement.

The first ionisation energy of potassium is smaller than the first ionisation energy of calcium.

2b2 marks

Explain the following statement.

The first ionisation energy of potassium is larger in value than rubidium

2c3 marks

Using section 9 of the data booklet, explain the trend of decreasing electronegativity values of the Group 17 elements from F to I.

2d1 mark

Define the term electronegativity.

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3a1 mark

Define what is meant by the term electron affinity.

3b1 mark

State whether first electron affinity is an exothermic or endothermic process.

3c2 marks

Write an equation, including state symbols, for the first electron affinity of bromine.

3d1 mark

State whether the first electron affinity of I is more or less exothermic than Br.

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4a2 marks

An element has the following electron configuration.

1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p4

i)
State which block of the periodic table the element is in.
[1]
ii)
State how many electrons it has in its outer shell.
[1]
4b3 marks

Magnesium can be ionised to form a cation, Mg+.

i)
Write the electron configuration of an Mg+.
[1]
ii)
Define the term ‘first ionisation energy'  in relation to magnesium.
[2]

4c1 mark

The periodic table can be divided into blocks.

State why are silicon, carbon, oxygen and chlorine all classified as p-block elements.

4d2 marks

This question is about the periodicity of period 3 elements.

i)
State the trend in atomic radius across period 3.
[1]
ii)

State the general trend in first ionisation energies across period 3.

[1]

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5a1 mark

Antimony, Sb, has atomic number 51.

Using Section 7 of the data booklet, complete the table to show where antimony is found in the periodic table.

Period

Block

   

5b1 mark

Identify the element that is in the d-block of the periodic table which forms a 3+ ion with the following electron configuration.

[Ar] 3d3

5c1 mark

Ionisation energies can provide evidence for electron structure.

Write an equation, including state symbols, for the first ionisation energy of chlorine.

5d1 mark

An element Y has the following six first ionisation energies in kJ mol-1. These are shown in the table below.

 

1st 

2nd

3rd

4th

5th

6th

Ionisation energy (kJ mol-1)

577

1820

2740

11 600

14 800

18 400

State what group of the periodic table this element belongs to.

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6a1 mark

State the changes in the acid-base nature of the oxides across period 3 (from Na2O to Cl2O7).

6b1 mark

Write an equation for the reaction of sodium oxide with water.

6c1 mark

Predict how the pH of water will change when phosphorus(V) oxide is added.

6d1 mark

What is the product when SOreacts with water.

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7a1 mark

State the equation for the reaction of sodium metal with water.

7b2 marks

Describe two changes that could be observed during the reaction of sodium metal with water.

7c1 mark

Predict the relative reaction rates of lithium, sodium and potassium with water.

7d2 marks

State two differences between the reactions of sodium and potassium with water.

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8a1 mark

State the balanced chemical equation for the reaction of potassium bromide, KBr (aq), with chlorine, Cl2 (g).

8b1 mark

Describe the colour change likely to be observed in the previous reaction.

8c1 mark
State the equation for the reaction between potassium and chlorine.
8d3 marks

Explain the trend in reactivity of the halogens.

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9a2 marks

Transition metals can form complex ions where ligands are coordinately bonded to the central metal ion.

i)    Define the term ligand.

[1]

ii)    State what is meant by the term bidentate ligand

[1]

9b2 marks

Transition metals are located in the d-block of the periodic table.

i)
State the electron configuration of V2+.

[1]

ii)
Explain why scandium is not considered a transition metal.

[1]

9c1 mark

State the oxidation state of Fe in [Fe(CN)6]4−.

9d3 marks

Iron and zinc are in the d-block of the Periodic Table. Iron(II) ions, [Fe(H2O)6]2+, form a pale green solution but zinc ions,   [Zn(H2O)6]2+, form a colourless solution.

i)
Write the electron configuration of Zn2+.
[1]
ii)
Explain why zinc ions are colourless.
[2]

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10a1 mark

State the formula of a bidentate ligand.

10b3 marks
State three factors that affect the value of the splitting energy, ΔE, in the d-orbitals.
10c5 marks

Outline why transition metals form coloured compounds.

10d2 marks

Explain why adding ammonia to aqueous copper(II) ions results in a darker blue complex.

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11a1 mark

Deduce the oxidation state of vanadium in the compound NH4VO3.

11b1 mark

Transition elements can be used to catalyse certain reactions.

Define the term heterogeneous in relation to catalysts.

11c1 mark

Describe the splitting of the d orbitals in an octahedral crystal field.

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1a4 marks

The periodic table displays the chemical elements, arranged in order of increasing atomic number. It is made up of groups and periods of elements.

State and explain the general trend in first ionisation energy across a period of the periodic table.

1b3 marks

The general trend in first ionisation energies stated in part (a) is seen across period 2 of the periodic table. However, boron and one other period 2 element deviate from this trend.

Identify this element and explain why it deviates from the general trend.

1c2 marks

State why nitrogen is classed as a p block element and give its full electron configuration.

1d3 marks

Identify the period 3 element that has the lowest melting point.

Explain your answer with reference to bonding and structure.

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2a3 marks

The first ionisation energy for all the elements is found in Section 9 of the IB data booklet.

i)
Define the term first ionisation energy of an element.
[2]
ii)
Write the equation for the first ionisation energy of aluminium.
[1]
2b2 marks

The table below shows successive ionisation energies of an element A, found in period 3 of the periodic table.

Table 1

Number of electrons

1

2

3

4

5

6

7

8

Ionisation Energy
(kJ mol-1)

1012

1907

2914

4964

6274

21268

25431

29872

  

Identify element A.

Explain your answer using data from Table 1.

2c5 marks

The graph below in Figure 1 shows some information on the elements of period 3 of the periodic table.

Figure 1

3-1-ib-chemistry-sq-q2c-medium

State and explain the trend that this graph shows, including why there are values that deviate from the trend.

2d1 mark

Explain why the second ionisation energy of aluminium is a larger value than the first ionisation energy. 

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3a3 marks

This question is about the structure of the periodic table.

Throughout the early history of the periodic table, scientists have attempted to order the elements according to different properties.

i)
State the property that is used to order the elements in the modern periodic table.
[1]
ii)
Outline how the electron configuration of elements is related to their group and period in the periodic table.
[2]
3b2 marks

This question is about the element phosphorus.

i)
State the group number, period number, and block in which you would find the element phosphorus.
[1]
ii)
State the full electron configuration of the phosphide ion, P3-.
[1]
3c2 marks

Outline why the atomic radius is seen to decrease across period 2 (from lithium to fluorine).

3d3 marks

Gallium forms an ion smaller than its element, whereas arsenic forms an ion larger than its element.

Explain these differences in ionic radius.

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4a3 marks

Bromine and selenium are both found in period 4 of the periodic table.

State and explain which of the two has a higher electronegativity.

4b2 marks

Sketch on the axes shown below in Figure 1, a graph of the first ionisation energy against atomic number for the elements of Group 1.

Figure 1

 3-1-ib-chemistry-sq-q4b-medium           

Explain the trend in ionisation energy down group 1.

4c3 marks

Discuss the similarities and differences between the trends in atomic radius and ionic radius down Group 1 and Group 17.

4d2 marks

State how the first ionisation energy of potassium differs from that of:

i)
Calcium.
[1]
ii)
Rubidium.
[1]

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5a2 marks

Group 17 elements are known as highly electronegative non-metal elements.

i)
Define the term electronegativity. 
[1]
ii)
State and explain the trend in electronegativity in Group 17. 
[1]
5b2 marks

Define the term electron affinity and write an equation to show the first electron affinity of bromine.

5c2 marks

State, with reasons, whether the first electron affinity of iodine is more or less exothermic than bromine.

5d2 marks

Suggest why the second electron affinity of oxygen is endothermic.

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6a2 marks

The hydrogen halides do not show perfect periodicity. A bar chart of boiling points, as seen in Figure 1, shows that the boiling point of hydrogen fluoride, HF, is much higher than periodic trends would indicate.

Figure 1

3-2-ib-chemistry-sq-q1a-medium

Explain why the boiling point of HF is much higher than the boiling point of the other hydrogen halides.

6b2 marks

There is an increase in boiling point moving from HCl to HI.

Explain this trend in boiling points of the hydrogen halides.

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7a3 marks

A student dissolves the oxides of potassium and selenium in water and tests the resulting solutions with litmus paper.

Explain what the student would expect to observe.

7b2 marks

Magnesium and silicon(V) oxides melt at high temperatures, unlike phosphorus(V) oxide and sulfur trioxide, which do so at lower temperatures.

State whether each of the four oxides would conduct electricity in their molten state.

7c2 marks

For the solutions formed by dissolving the oxides in water in part (b), identify each as acidic, alkaline, or neutral.

7d3 marks

Write equations for each of the reactions when the oxides of magnesium, phosphorus, and sulfur in part b) are dissolved in water.

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8a2 marks

Sodium oxide and silicon dioxide are two compounds of period 3 elements that react with water. Write equations for their separate reactions with water.

8b2 marks

Suggest the pH of the resulting solutions when both sodium oxide and phosphorus(V) oxide react with water.

8c3 marks

Aluminium oxide can react as both an acid and as a base.

i)
State the name given to this type of oxide. 
[1]
ii)
Write an equation for the reaction of aluminium oxide with hydrochloric acid. 
[1]
iii)
State whether aluminium oxide is behaving as an acid or base in this reaction.
[1]

8d3 marks

Outline the acid-base nature of the oxides of the elements in period 3 from sodium to chlorine

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9a2 marks

Potassium is an element found in group 1 of the periodic table.

State how potassium reacts with water and write a balanced equation for the reaction including state symbols.

9b3 marks

A student has a sample of lithium and sodium which he drops into a beaker of distilled water.

Compare the reactivity of lithium and sodium with water and state what the student would see in each reaction.

9c3 marks

The student continues to react various group 1 metals with water and observes a change in reactivity as they move down the group.

Explain the trend in reactivity that would be observed.

9d2 marks

From only the first three elements in each of Group 1 and Group 17, state which Group 1 element and Group 17 element would show the most vigorous reaction when they react together.

Write a balanced equation for the reaction.

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10a3 marks

Chlorine is a greenish-yellow gas, bromine is a dark red liquid, and iodine is a dark grey solid.

State and explain the property which most directly causes these differences in volatility.

10b2 marks

Explain why Cl2 rather than Br2 would react more vigorously with a solution of I-.

10c3 marks

Describe what happens when aqueous bromine solution is added to separate solutions of sodium chloride and sodium iodide.

Include balanced equations for any reactions that occur.

10d2 marks

Astatine, At, is the rarest naturally occurring element in the Earth’s crust. Before it was discovered in 1940 scientists could only predict its existence and properties.

Suggest the basis for these predictions.

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11a2 marks

Explain why transition metals exhibit variable oxidation states compared to the elements in Group 1.

11b3 marks

Transition metal compounds and ions are often coloured. For example, [Cr(H2O)6]3+ is green. 

Explain why [Cr(H2O)6]3+ and other complex ions are coloured.

11c3 marks

Water acts as a ligand when it reacts with zinc and cobalt ions, forming the complexes [Zn(H2O)4]2+ and [Co(H2O)6]2+ 

Explain how water acts as a ligand in forming these complexes and predict the shape of [Co(H2O)6]2+.

11d4 marks

Explain why solutions containing [Co(H2O)6]2+ are coloured but solutions containing [Zn(H2O)4]2+ are not.

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12a3 marks

Complete Table 1 below to show the oxidation state of the transition element.

Table 1

Ion

[Cu(Cl4)]2-

[Fe(H2O)6]3+

Cr2O72-

Oxidation state

 

 

 

12b3 marks

EUK-134 is a complex ion of manganese(III) used in skin care products to protect against UV damage as it has antioxidant properties.

q2c_13-1_medium_ib_hl_sq

i)
State the electron configuration of the manganese(III) ion in the complex shown above.
[1]
ii)
State the name given to species that bond to a central metal ion, and identify the type of bond present.
[2]

12c2 marks

Transition metals have certain characteristic properties.

State two properties that are involved in EUK-134 rapidly decreasing the concentration of oxidising agents. 

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13a5 marks

A characteristic property of transition elements, like chromium, is that they form coloured compounds. Explain why Ni2+(aq) is green but Sc3+(aq) is colourless.

13b3 marks

The colour intensity of solutions of complex ions is one method of determining the concentration of transition metal ions. Excess aqueous ammonia is sometimes added before measuring the absorption of copper(II) ions. 

Describe why the addition of excess ammonia to aqueous copper(II) ions causes the shade of the blue colour to change.

13c2 marks

Increasing the concentration of chloride ions in an aqueous solution of vanadium(III) chloride causes the vanadium complex to change from [V(H2O)6]3+ to [VCl (H2O)5]2+ to [VCl2(H2O)4]+ 

Outline what would happen to the wavelength at which the vanadium complex ions would absorb light as the concentration of chloride ions is increased.

13d2 marks

Ferrocyanide salts,  [Fe(CN)6]4−, are used in the production of Prussian blue, which was the first modern synthetic pigment.

i)
Deduce the oxidation number of iron in [Fe(CN)6]4−.
[1]
ii)
Draw the abbreviated orbital diagram for the iron ion in [Fe(CN)6]4– using the arrow-in-box notation to represent electrons.
[1]

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14a1 mark

The energy level diagram showing the electrons in the five 3d orbitals of a chromium atom is shown in the figure below. 

Draw the completed diagram showing the d orbitals in [Cr(H2O)6]3+ after splitting.

q4a_13-1_medium_ib_hl

14b2 marks

State and explain what happens to the splitting of the d orbitals if the ligand is changed from H2O to NH3.

14c2 marks

Explain, in terms of acid-base theories, what type of a reaction is the formation of [Fe(H2O)6]2+ from Fe2+ and water.

14d4 marks

The complex ion [Ni(NH3)6]2+ is blue and [Ni(H2O)6]2+  is green 

Explain why the  [Ni(H2O)6]2+ complex ion is coloured and outline why changing the identity of the ligand changes the colour of the ion.

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15a4 marks

Dilute copper(II) chloride solution is light blue, while copper(I) chloride is colourless. 

Describe how the blue colour is produced in the copper(II) chloride. Refer to Section 15 of the Data Booklet.

15b2 marks

Explain why the copper(I) chloride is colourless.

15c2 marks

When excess ammonia is added to copper(II) chloride solution, the dark blue complex ion, [Cu(NH3)4(H2O)2]2+, forms. 

State the molecular geometry of this complex ion and the bond angles within it.

15d3 marks

Outline the relationship between the Brønsted–Lowry and Lewis definitions of a base, referring to the ligands in the complex ion [CuCl4]2−.

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1a3 marks

This question refers to the elements in the first three periods of the Periodic Table.

Select an element from the first three periods that fits each of the following descriptions.

i)
The element with the highest first ionisation energy

[1]

ii)
The element that forms a 1 ion with the same electron configuration as helium

[1]

iii)
An element which forms a compound with hydrogen in which the element has an oxidation number of −4

[1]

1b5 marks

This question is about the elements which have atomic numbers 33 to 37.

The first ionisation energies of these elements are shown in the table below.

Element

As

Se

Br

Kr

Rb

Ionisation energy value in kJ /mol-1

947

941

1340

1351

403

i)
Suggest the formulae of the hydrides of arsenic and selenium

[2]

ii)
Explain why the first ionisation energy of rubidium is lower than that of krypton

[2]

iii)
State which of the elements, arsenic to rubidium, has atoms with the smallest atomic radius

[1]

1c3 marks

The first 3 elements of Period 3 show a general increase in melting point.

Explain this trend in melting point across these Period 3 elements.

1d3 marks

This question is about hydrogen, the element with the atomic number Z = 1.

Hydrogen can be placed in several different positions in periodic tables. One is immediately above lithium in Group 1 as shown in section 6 of the data booklet. Another is in the centre of the first row.

Evaluate the position of hydrogen when it is placed immediately above lithium and state one reason in favour and two against. 

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2a2 marks

This question is about Period 4 of the Periodic Table. 

State and explain which of K+ and Ca2+ is the smaller ion.

2b1 mark

Write the electron configuration for a Ca+ ion.

2c4 marks

The first ionisation energies of the elements H to K are shown below.

periodicity-diagram-1

State and explain the trend in first ionisation energies shown by the elements with the atomic numbers 2, 10 and 18.

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3a3 marks

Electrons in atoms occupy orbitals.

The figure below shows the first ionisation energies for six consecutive elements labelled AF

periodicity-diagram-2

Complete the graph of the first ionisation energies for the next five elements.

3b2 marks

Explain why the value of the first ionisation energy for D is greater than for C.

3c4 marks

The sequence of the first three elements in the Periodic Table is hydrogen, helium and then lithium.

Explain why the first ionisation energy of hydrogen is less than that of helium but greater than that of lithium.

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4a3 marks

First ionisation energies decrease down groups in the Periodic Table.

Explain this trend and the effect on the reactivity of groups containing metals.

4b3 marks

The ionisation energy values show a general increase across period 4 from gallium to krypton.

State and explain how selenium deviates from this trend. 

4c1 mark

Give one other element from period 2 or 3 which also deviates from this general trend, similar to selenium.

4d6 marks

State and explain the trends in electronegativity down group 2 and across period 3.

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5a1 mark

Describe the trends in first ionisation energy and atomic radius as you move up Group 1. 

5b2 marks
Explain the connection between first ionisation energy and atomic radius seen in the alkali metals.
5c3 marks

Potassium reacts with water to form hydrogen gas. Using sections 1 and 2 of the data booklet, determine the volume, in cm3, of hydrogen gas that could theoretically be produced at 273 K and 1.01105 Pa when 0.0587 g of potassium reacts with excess water.

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6a3 marks

Write equations for the separate reactions of lithium oxide and carbon dioxide with excess water and differentiate between the solutions formed. 


Lithium oxide
................

Carbon dioxide.............

Differentiation..............

6b1 mark

Suggest why it is surprising that dinitrogen monoxide dissolves in water to give a neutral solution.

6c1 mark

Calcium carbide reacts with water to form ethyne, C2H2, and one other product.

Estimate the pH of the resultant solution.

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7a
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3 marks

Impurities cause phosphine to ignite spontaneously in the air to form an oxide of phosphorus and water.

The oxide formed in the reaction with air contains 56.3 % phosphorus by mass. Determine the empirical formula of the oxide, showing your method.

7b
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1 mark

The molar mass of the oxide is approximately 220 g mol−1. Determine the molecular formula of the oxide.

7c1 mark

State the equation for the reaction of this oxide of phosphorus with water.

7d1 mark

Predict how dissolving an oxide of phosphorus would affect the electrical conductivity of water.

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8a4 marks

When chromium(III) sulfate dissolves in water, a green solution containing the [Cr(H2O)6]3+ ion forms.

i)
State the bond angles found in this complex ion.
[1]
ii)
Explain why the chromium(III) complex ion is coloured.
[3]
8b2 marks

Vanadium(V) oxide is the catalyst used in the Contact process as shown by the reactions:

SO2 (g) + V2O5 (s) → SO3 (g) + V2O4 (s)

V2O4 (s) + ½O2 (g) → V2O5 (s)

i)     Explain, using the equations, why V2O5 is a catalyst.

[1]

ii)     Explain why V2O5 can act as a catalyst in this reaction.

[1]
8c1 mark

Excess ammonia is added to a solution of Cu2+ ions resulting in the substitution of 4 ligands.

Explain why this reaction results in a shift in the wavelength of light absorbed by the Cu2+ complex.

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9a1 mark

Iron is a transition element that forms several ions with iron in different oxidation states.

Deduce the condensed electron configuration of the iron cation that can form the complex ion [Fe(CN)6]4−.

9b2 marks

Co(III) has the same electron configuration as the iron cation in part(a). 

Explain why, despite this, solutions of the two ions are different colours.

9c1 mark

Rhenium forms salts containing the perrhenate(VII) ion, ReO4.

Suggest why the existence of salts containing an ion with this formula could be predicted. Refer to section 7 of the data booklet.

9d2 marks

Rhenium is used with platinum to speed up reactions used in the production of gasoline.

Predict two other chemical properties you would expect rhenium to have, given its position in the periodic table.

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10a2 marks

1,2-diaminoethane is a bidentate ligand which can form a complex with [Co(NH3)4(H2O)2]2+. In this reaction, only the ammonia molecules are replaced.                                              

i)    Write an equation for this reaction.

[1]

ii)          State the molecular geometry of the complex formed.

[1]

10b2 marks

Explain why Ti forms variable oxidation states, but Ca only occurs in the +2 oxidation state. 

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11a2 marks

The following three step synthesis route was carried out:

rightwards arrow with straight i right parenthesis space straight H subscript 2 SO subscript 4 space ii right parenthesis space straight H subscript 2 straight O on top  B rightwards arrow with straight K subscript 2 Cr subscript 2 straight O subscript 7 space plus space straight H subscript 2 SO subscript 4 on top  rightwards arrow with straight H subscript 2 SO subscript 4 on top

Reactant A is a hydrocarbon containing 85.71% carbon and shows 4 peaks in a 1H NMR spectrum. Deduce the identity of A.

11b
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2 marks

Intermediate B shows a fragment at m/z 43 in the mass spectrum and has a molecular ion at m/z 74.

Deduce the identity of B, giving a reason.

11c2 marks

The question is about intermediate C in the synthesis.

i)
Suggest an identity for intermediate C.

[1]

ii)
State the reaction conditions for the conversion of B to C.
[1]
11d2 marks

Deduce the identify of the reaction product, D, and give one piece of spectral data that would support your answer.

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