IGCSEChemistry: Double ScienceEdexcelExam Questions2. Inorganic ChemistryGroup 1 (Alkali Metals)

Group 1 (Alkali Metals) (Edexcel IGCSE Chemistry: Double Science)

Exam Questions

1 hour12 questions
Medium
Hard
1a1 mark

This question is about the elements in Group 1 of the Periodic Table and their reactions with water.

a)
State why sodium and potassium are in Group 1 of the Periodic Table.
[1]

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1b5 marks
b)
A reaction occurs when a small piece of sodium is added to a large volume of water in a trough.

i)
Give two observations that you would make during this reaction.
[2]
ii)
After the reaction has finished, a few drops of universal indicator are added to the solution in the trough. Explain the final colour of the universal indicator.
[2]
iii)
What is the most likely pH value of the solution in the trough after the reaction is complete?

  ☐ A 2
  ☐ B 5
  ☐ C 8
  ☐ D 12

[1] 

 

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1c1 mark
c)
Give the name of a Group 1 metal that is less reactive than sodium.
[1] 

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1d1 mark
d)
A small piece of potassium is added to a large volume of water in a trough.
Give one observation that is made when potassium is added to water that is not made when sodium is added to water.

[1] 

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1e1 mark
e)
Complete the equation for the reaction of rubidium with water. State symbols are not required.

........Rb + ........H2O → ........RbOH + .........H2

[1] 

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21 mark

This question is about the reaction between sodium and water.

Which statement about this reaction is correct?

(1)

  ☐ A Sodium sinks to the bottom of the water
  ☐ B A lilac flame is seen
  ☐ C A solution of sodium oxide is produced
  ☐ D Bubbles of hydrogen gas are produced 

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3a7 marks

This question is about some of the Group 1 elements and their compounds.

a)
A teacher adds a small piece of lithium to water in a trough.
 
i)
Give three observations that are made when lithium reacts with water.
 
(3)
 
ii)
After the reaction has finished, the teacher adds a few drops of universal indicator to the solution in the trough.
 
Explain the colour of the universal indicator after it is added to the solution.
 
(2)
 
iii)
Write a chemical equation for the reaction of lithium with water.
 
(2)

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3b3 marks
b)
A student does a flame test to see if a white solid contains sodium ions.
 
She cleans a platinum wire before using it for the flame test.
 
i)
Explain why the student needs to clean the platinum wire.
 
(2)
 
ii)
Which of these is the colour of the flame if the solid contains sodium ions?
 
(1)
 
  ☐ A green
  ☐ B lilac
  ☐ C red
  ☐ D yellow

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3c5 marks
c)
Potassium sulfate (K2SO4) is an ionic compound.
 
i)
Give the formula of each ion in potassium sulfate.
 
(1)
potassium ion ..................    
sulfate ion ...............
 
ii)
The melting point of potassium sulfate is 1069 °C.
 
Explain why potassium sulfate has a high melting point.
 
Refer to structure and bonding in your answer.
 
(4)

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41 mark

When lithium, a Group 1 metal, reacts with water, two products are formed.

Which is the correct balanced symbol equation, including state symbols, that represents this reaction?

(1)

  ☐ A Li (s) + 2H2O (l)  →  Li(OH)2 (l) + H2 (g)
  ☐ B 2Li (s) + 2H2O (l)  →  2LiOH (aq) + H2 (g)
  ☐ C 2Li (s) + H2O (l)  →  Li2O (aq) + H2 (g)
  ☐ D 2Li (s) + 2H2O (l)  →  2LiOH (l) + O2 (g)

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5a3 marks

This question is about some elements in Group 1 of the Periodic Table.

a)
The table gives some statements about the reaction of potassium with water.

Place ticks (✔) in three boxes to show which three statements are correct.

Statement  
 potassium reacts more vigorously than sodium when added to water  
 potassium sinks to the bottom of the water  
 bubbles of oxygen gas are produced  
 a lilac flame is seen  
 potassium moves around  
 a solution of potassium oxide is formed  

(3)

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5b2 marks
b)
After the reaction of potassium with water is complete, a few drops of universal indicator are added to the solution formed. The universal indicator turns purple.

i)
Suggest a value for the pH of the solution.

(1)

ii)
Give the formula of the ion responsible for this pH value.

(1)

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5c1 mark
c)
Sodium burns in oxygen to produce sodium oxide.

Complete the equation for this reaction.

..........Na + ..........O2 → ..........Na2O

(1)

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61 mark

Which of the following could not be predicted about caesium, based on the trends seen in Group 1 metals?

(1)

  ☐ A It is soft
  ☐ B It has a relatively high melting point
  ☐ C It is very reactive
  ☐ D It has a relatively low density 

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7a1 mark

Lithium, sodium and potassium are the first three elements in Group 1 of the Periodic Table.

a)
Suggest why these three elements are all stored in paraffin oil.
(1)

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7b4 marks
b)
Caesium, Cs, is below potassium in Group 1.
i)
Give a similarity and a difference between the reactions of potassium with water and caesium with water.

similarity..........................................................

difference........................................................
(2)
ii)
Give the chemical equation for the reaction between caesium and water.
(2)

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7c3 marks
c)
A student investigates the temperature change in the reaction between dilute acids and solutions of Group 1 hydroxides.
He uses this apparatus.
temperature-change-apparatus
 

This is the student’s method:

  • Measure the temperature of 50 cm3 of hydrochloric acid
  • Pour the acid into a polystyrene cup
  • Add 50 cm3 of sodium hydroxide solution to the acid
  • Measure the maximum temperature of the mixture
i)
Suggest what could be added to the apparatus to improve the experiment.
(1)
ii)
Explain a change to the method that would improve the accuracy of the experiment.
(2)

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7d
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d)
These are the student’s results:

Temperature of hydrochloric acid = 19.9 °C
Maximum temperature of mixture = 26.5 °C
 
i)
Calculate the energy change, Q, in joules for this reaction.
[mass of 1.0 cm3 of mixture = 1.0 g]
[for the mixture, c = 4.2 J / g / °C]

Q = .............................................. J
(3)
ii)
In the student’s reaction between hydrochloric acid and sodium hydroxide, 0.050 mol of water forms.

Calculate the molar enthalpy change, ΔH, in kJ / mol for this reaction.

ΔH = .............................................. kJ / mol

(2)

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81 mark

The position of an element in the Periodic Table can be used to predict its properties.

Which of the following statements could not be predicted using the trends in Group 1?

(1)

  ☐ A Rubidium has a lower melting point than lithium
  ☐ B Lithium is softer than potassium
  ☐ C Sodium will tarnish more quickly than lithium
  ☐ D Caesium is more reactive than potassium

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91 mark

A teacher adds a small piece of potassium to a large trough of water to form a solution.

When the reaction has completed she adds a few drops of universal indicator to the solution.

What is the most likely pH value of the solution?

(1)

  ☐ A 3
  ☐ B 7
  ☐ C 8
  ☐ D 12

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10a3 marks

This question is about the reactions of Group 1 metals with water.

a)
A teacher adds a piece of sodium to some water containing universal indicator.
 
sodium-in-water-trough
 
The equation for this reaction is:
 
2Na (s) + 2H2O (l) → 2NaOH (aq) + H2 (g)
 
The sodium floats on the surface of the water and the universal indicator changes colour because an alkaline solution is formed.
 
i)
Give two other observations.
 
(2)
 
ii)
Give the final colour of the universal indicator.
 
(1)

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10b4 marks
b)
The diagram represents an atom of lithium and an atom of sodium.
 
li na
lithium sodium
 
i)
Give a reason why lithium and sodium have similar reactions with water.
 
(1)
 
ii)
Explain why lithium is less reactive than sodium.
 
(3)

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11a2 marks

This question is about some of the alkali metals and their compounds.

a)
When a teacher drops a small piece of sodium into a trough of cold water, she observes bubbles of gas.
 
Give two other observations that would be made when sodium reacts with cold water.
 
(2)

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11b6 marks
b)
Lithium reacts with fluorine to form the compound lithium fluoride.
 
i)
Give a chemical equation for this reaction.
 
(1)
 
ii)
Give a test to show that lithium fluoride contains lithium ions.
 
(2)
 
iii)
Draw diagrams to show the arrangement of the electrons in a lithium ion and in a fluoride ion.
Include the charge on each ion.
 

(3)

Lithium ion

 

 

 

 

 Fluoride ion

 

 

 

 

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1a3 marks

This question is about Group 1 metals and their reactions.

a)
When lithium is added to water, bubbles of hydrogen gas are observed.

i)
Give two other observations that could be made.
(2)
ii)
Give the test for hydrogen gas.
(1)

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1b4 marks
b)
   
i)
Give one observation that would be different if potassium is used instead of lithium.
(1)

ii)
The diagram represents an atom of lithium and an atom of potassium.

lithium-and-potassium-electron-structures
Explain why potassium is more reactive than lithium.
(3)

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1c
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c)
The equation for the reaction between lithium and water is:

2Li (s) + 2H2O (l) → 2LiOH (aq) + H2 (g)

i)
A mass of 0.500 g of lithium reacts with an excess of water.
Calculate the volume, in cm3, of hydrogen gas produced at rtp.
[molar volume of a gas at rtp = 24 000 cm3]

Give your answer to three significant figures.
(3)




volume = .......................................... cm3

ii)
In a reaction between lithium and water, 150 cm3 of lithium hydroxide solution is formed.
The lithium hydroxide solution is then completely neutralised by 24.85 cm3 of 0.100 mol/dm3 sulfuric acid.

The equation for the neutralisation is

2LiOH (aq) + H2SO4 (aq) → Li2SO4 (aq) + 2H2O (l)

Calculate the concentration, in mol/dm3, of the lithium hydroxide solution.
(3)



concentration = .............................................................. mol/dm3

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