Syllabus Edition

First teaching 2023

First exams 2025

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The Ionic Model (HL IB Chemistry)

Exam Questions

2 hours22 questions
1a1 mark

Define ionic bonding.

1b1 mark

State the type of bonding in potassium chloride which melts at 1043 K.

1c2 marks

Describe the structure and bonding in solid magnesium oxide.

1d1 mark

Outline why solid magnesium chloride does not conduct electricity.

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2a2 marks

Predict whether phosphorus(V) oxide and sodium oxide conduct electricity in their solid and molten states. Complete the boxes with “yes” or “no”.

  Phosphorus(V) oxide Sodium oxide
Solid state    
Molten state    
2b2 marks

State the formula of the compounds formed between the elements below.

i)    Sodium and sulfur.

[1]

ii)    Magnesium and phosphorus.

[1]

2c2 marks

Describe the covalent bond present in a chlorine molecule and how it is formed.

2d1 mark

Draw the Lewis (electron dot) structure of chloromethane.

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3a2 marks

This question is about ionic lattices.

i)
State the definition of lattice enthalpy, ΔHθlatt
[1]
ii)
Explain why lattice enthalpy is always endothermic
[1]

3b2 marks

Magnesium forms a stable ion of Mg2+

i)
Which noble gas has the same electronic structure as Mg2+?

[1]

ii)
Write the electronic structure of the magnesium ion, Mg2+, in full

[1]

3c3 marks

Predict the electrical conductivity of magnesium fluoride in each of the following states:

 
State Electrical conductivity (Y / N)
Solid  
Liquid  
Aqueous  

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1a2 marks

Calcium sulfide is an ionic solid that is phosphorescent and glows in the dark after a light source is removed.

i)
Describe the nature of the bonding in calcium sulfide.

[1]

ii)
State one physical property of calcium sulfide.

[1]

1b3 marks

Suggest why the melting point of calcium sulfide is much higher than that of elemental calcium or sulfur.

1c4 marks

Calcium sulfide has a lattice structure similar to sodium chloride.

Describe the lattice structure of calcium sulfide and draw a representative 3D diagram.

Label each ion and use different size spheres to distinguish between the different types of ions present.

1d2 marks

State the formula of calcium phosphate and calcium hydroxide.

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2a2 marks

The table shows the properties of four substances.

substance boiling point electrical
conductivity of solid
electrical conductivity
when molten
copper high conducts conducts
lithium bromide high does not conduct conducts
sulfur low does not conduct does not conduct

State the meaning of the term ionic bonding.

2b2 marks

Identify the information in the table that shows that lithium bromide is an ionic compound.

2c4 marks

Lithium bromide dissolves in organic solvents, whereas potassium fluoride is insoluble in organic solvents. 

Suggest a reason for the difference in solubility in organic solvents.

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3a2 marks

Strontium nitride reacts with water to form strontium hydroxide and ammonia.

Write the balanced symbol equation for this reaction. 

3b2 marks

Strontium nitride has a melting point of 1200 °C. 

i)
Explain why its melting point is high.
[1]
ii)
State and explain the conditions under which strontium nitride will act as an electrical conductor.

[3]

3c2 marks

The melting point of magnesium nitride is 1500 °C. Explain the difference between the melting point for strontium nitride and magnesium nitride.

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1a5 marks

Magnesium fluoride is a white crystalline salt that has a giant ionic lattice structure.

State whether the following substances conduct electricity when solid or molten, and explain your answers in terms of the particles involved:

  • magnesium
  • magnesium fluoride
  • boron tribromide
1b2 marks

Sodium chloride and iodine are both solids. Sodium chloride does not melt until it reaches a temperature of 1074 K yet iodine sublimes when heated gently, giving off purple vapours. Sodium chloride will conduct electricity when molten and iodine is a very poor conductor of electricity.

State the type of crystal structure for each of iodine and sodium chloride.

1c2 marks

Explain why iodine vaporises easily.

1d3 marks

Explain the differences in the electrical conductivity of sodium chloride and iodine.

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2a2 marks

The nitrate (V) ion, NO3-, is a polyatomic ion, bonded by covalent bonds. 

The three oxygen atoms are bonded by one single covalent bond, one double covalent bond and one dative covalent bond.

Draw the Lewis structure for NO3-

2b2 marks

An ionic compound has the empirical formula H4N2O3

Suggest the formulae of the ions present in this compound.

2c4 marks

The compounds SO2 and MgO are both oxides but with different melting points as shown below.

Compound

Melting point / ℃

SO2

-72

MgO

2852

Describe the bonding in, and the structure of, SO2 and MgO and explain the difference in their melting points.

2d2 marks

Ammonia, NH3, has the same crystalline structure as SO2 and yet its melting point is 2 oC. Explain the difference in melting point between SO2 and NH3.

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3a4 marks

This question is about ionic compounds.

The table shows the formulae of some positive and negative ions, and the formulae of some compounds containing these ions.

  Mg2+ Al3+ NH4+
S2- MgS Al2S3  
NO3-   Al(NO3)3 NH4NO3
CO32- MgCO3   (NH4)2CO3

i)
Complete the table by giving the three missing formulae.

[3]

ii)
Give the name of the compound with the formula NH4NO3

[1]

3b7 marks

Magnesium nitrate is an ionic compound. Explain the following physical properties in terms of its structure:

i)
Volatility
[2]
ii)
Electrical conductivity
[2]
iii)
Solubility
[3]

3c2 marks

Write an equation to show the lattice enthalpy for magnesium sulfide

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