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

This question is about the reaction between sodium and water.

Which statement about this reaction is correct?

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

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

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)

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?

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?

\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)

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.

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)