Group 1 (alkali metals) (Edexcel IGCSE Chemistry (Modular): Unit 2)

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

State why sodium and potassium are in Group 1 of the Periodic Table.

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?

(1)  

Give the name of a Group 1 metal that is less reactive than sodium.

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.

Complete the equation for the reaction of rubidium with water. State symbols are not required.

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

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

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)

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)

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)

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?

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

The table gives some statements about the reaction of potassium with water. Place ticks (✔) in three boxes to show which three statements are correct.

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)

Sodium burns in oxygen to produce sodium oxide. Complete the equation for this reaction.

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

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?

This question is about sodium and potassium.

A trough is filled with water and a few drops of phenolphthalein indicator are added.

 A small piece of sodium is dropped into the water. One of the products of the reaction is an alkali.

i) Complete the chemical equation for the reaction of sodium with water.

(2)

___Na (.......) + ___H₂O (l) → ___NaOH (........) + H₂ (g)

ii) Identify the ion that causes the solution to become alkaline.

(1)

iii) Give three observations that would be made when sodium reacts with water.

(3)

Separate: Chemistry Only

Explain why potassium is more reactive than sodium. Refer to the electronic configurations of the atoms in your answer.

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

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.

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)

Separate: Chemistry Only

The table shows the electronic configurations of sodium and potassium. 

Explain, in terms of their electronic configurations, why potassium is more reactive than sodium.

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

Suggest why these three elements are all stored in paraffin oil.

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)

A student investigates the temperature change in the reaction between dilute acids and solutions of Group 1 hydroxides.

He uses this 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)

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)

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

A teacher adds a piece of sodium to some water containing universal indicator.

 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)

The diagram represents an atom of lithium and an atom of sodium. 

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)

Separate: Chemistry Only

 The teacher adds 0.150 g of lithium to an excess of water and collects the hydrogen gas produced.

 The equation for the reaction is 

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

The teacher collects 254 cm³ of hydrogen gas at room temperature and pressure (rtp). 

Show by calculation that 1 mol of hydrogen gas has a volume of approximately 24000 cm³ at rtp.

This question is about Group 1 metals and their reactions.

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)

Separate: Chemistry Only  

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.

Explain why potassium is more reactive than lithium.

(3)

Separate: Chemistry Only

 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

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

When a teacher drops a small piece of potassium into a trough of cold water, they observe bubbles of gas. 

Give two other observations that would be made when potassium reacts with cold water.

When the reaction between potassium and cold water is complete, the teacher adds some universal indicator to the trough. 

Explain the final colour of the universal indicator.

Suggest why the teacher does not repeat the experiment using hydrochloric acid instead of cold water.

Separate: Chemistry Only  

i) Give the balanced chemical equation for the reaction of potassium with hydrochloric acid. State symbols are required.

 (2)

 ii) Draw diagrams to show the arrangement of the electrons in the product of this reaction.

 (2)

This question is about some Group 1 metal oxides.

When lithium is exposed to oxygen, it is oxidised and traces of lithium peroxides are produced. 

i) Explain why the formation of lithium oxide is a redox reaction.

 (3)

 ii) Lithium oxide and a gas are produced by the thermal decomposition of lithium peroxide, Li₂O₂.

 Write the balanced chemical equation for this reaction. State symbols are not required.

 (2)

Lithium oxide can also be produced by heating lithium hydroxide. 

2LiOH → Li₂O + H₂O

 State the type of reaction that occurs during this process.

The oxidation of potassium can produce potassium oxide, K₂O, and potassium superoxide, KO₂. 

Compare the oxidation of potassium with the combustion of carbon.

Potassium superoxide is sometimes used as a water dehumidifier, carbon dioxide scrubber and oxygen generator on board space craft and submarines. 

As it absorbs and reacts with carbon dioxide, it locks the carbon dioxide up as potassium carbonate and releases oxygen.

 i)mWrite the balanced chemical equation for this chemical reaction. State symbols are not required.

 (2)

 ii) Determine the number of moles of carbon dioxide absorbed and the number of moles of oxygen released by one mole of potassium superoxide.

 (2)