A LevelChemistryCIETopic Questions2. Atoms, Molecules & Stoichiometry2.2 The Mole & the Avogadro Constant

Syllabus Edition

First teaching 2023

First exams 2025

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The Mole & the Avogadro Constant (CIE A Level Chemistry)

Topic Questions

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Easy
Medium
1a1 mark
Give the number of particles in one mole of a chemical.
 

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1b3 marks

i)       Give the number and type of atoms present in a molecule of water. 

[2]
 
ii)
Calculate the total number of particles and atoms present in one mole of water. 

[1]

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1c4 marks

i)

Give the number and type of ions present in one mole of sodium carbonate, Na2CO3.
[2]
 
ii)
Calculate the number of metal ions present in two moles of sodium carbonate.

[2]

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1d
Sme Calculator7 marks

i)       State the conditions when one mole of a gas occupies a volume of 24.0 dm3.

[2]
ii)
Complete Table 2.1.
Table 2.1
 
Gas Number of moles Volume of gas (dm3) Number of molecules present
Nitrogen 2.0 48.0  
Sulfur dioxide   1.8  
Carbon monoxide     9.03 x 1023
 
[5]

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1a
Sme Calculator3 marks

5.0 g of an unknown Group 2 nitrate was decomposed to produce 0.0843 moles of gas.

2X(NO3)2 (g) → 2XO (s) + 4NO2 (g) + O2 (g)

i)
Calculate the amount, in moles, of the unknown Group 2 nitrate.


.................... moles
[1]
ii)
Calculate the number of ions in the unknown Group 2 nitrate.


....................................... ions
[2]

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1b
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Identify the unknown element in the unknown Group 2 in part (a).

X = ............................

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1c2 marks

State and explain whether strontium nitrate would need to be heated more or less strongly than X(NO3)2 to decompose.

Relative strength of heating .......................................................................................

Explanation ..................................................................................................................

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2a
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Barium sulfate is a white insoluble solid and is used in stomach X-rays and as a pigment for paint.

Calculate the number of atoms in 74 mg of barium sulfate.

.............................................. particles

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2b1 mark

State the ionic equation for the formation of barium sulfate.

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2c
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A different barium compound, barium carbonate, was reacted with hydrochloric acid. 

i)
Write the balanced symbol equation for this reaction.
[1]
ii)
0.03 moles of carbon dioxide were formed in this reaction. Calculate the number of hydrogen ions that reacted.
[2]

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3a
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When magnesium reacts with hydrochloric acid, the following reaction occurs:

Mg (s) + 2HCl (aq) → MgCl2 (aq) + H2 (g)  

During the reaction, the hydrogen produced occupies 103 cm3 at 25.0 oC and 100 kPa. 

Calculate the amount, in moles, of hydrogen gas produced during the reaction. 



....................................... moles

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3b
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A student completed the same reaction as in part (a), using 3.75 g of magnesium.

Calculate the mass, in grams, of magnesium chloride produced by the student during this reaction. Give your answer to 3 significant figures.




.............................. g

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3c
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Calculate the number of hydrogen atoms produced during the student's reaction in part (b).

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