Group 7 (halogens) (Edexcel IGCSE Chemistry (Modular): Unit 2)

This question is about some of the halogens and their compounds.

i) Which element is a liquid at room temperature?

(1)

 ii) Which element has the palest colour?

(1) 

 iii) Which element is the least reactive?

(1)

A teacher uses displacement reactions to demonstrate the reactivities of some halogens. She adds solutions of chlorine, bromine and iodine separately to three different sodium halide solutions. The table shows some of the teacher’s results.

A change in colour of the solution indicates that a reaction has occurred.

i) Complete the table by predicting the missing results.

(2)

ii) State why the teacher does not add bromine solution to sodium bromide solution.

(1)

iii) The word equation for the reaction of bromine with sodium iodide is

bromine + sodium iodide → iodine + sodium bromide

Write a chemical equation for this reaction.

(1)

A technician sees an unlabelled bottle containing a liquid. He knows that the liquid is a solution of one of these compounds.

• copper(II) chloride

• copper(II) bromide

• iron(II) chloride

• iron(II) bromide

Describe chemical tests that the technician could use to identify the compound in the solution.

Astatine is found below iodine in Group 7 of the Periodic Table.

What is its formula and state at room temperature?

The reaction between aqueous chlorine and aqueous potassium bromide results in the formation of an orange solution.

Which is the correct statement about this reaction?

Bromine water is an aqueous solution of bromine which is orange in colour.

What would be seen if bromine water was added to the test tubes in the diagram?

The table gives some information about the halogens, chlorine, bromine and iodine.

Complete the table.

Chlorine has two isotopes of mass numbers 35 and 37. The relative percentage of each isotope in a sample of chlorine is

chlorine-35 77.78%    chlorine-37 22.22%

Calculate the relative atomic mass of this sample of chlorine. Give your answer to one decimal place.

Relative atomic mass = .........................

A student is given an aqueous solution of chlorine and an aqueous solution of potassium bromide.

Explain how he can use these two solutions to compare the reactivity of chlorine with the reactivity of bromine.

Separate: Chemistry Only

 The ionic equation for the reaction between chlorine and sodium bromide is:

Cl₂ (g) + 2Br^– (aq) → 2Cl^– (aq) + Br₂ (aq)

This reaction occurs because chlorine is more reactive than bromine.

Which of the statements explaining why chlorine is more reactive than bromine is not true?

This question is about the halogens.

The table gives some information about the halogens. Complete the table by predicting the physical state of astatine at room temperature and the colour of astatine.

Bromine has two isotopes with mass numbers 79 and 81

i) The relative percentages of each isotope in a sample of bromine are

bromine-79 = 51.0%                   bromine-81 = 49.0%

Calculate the relative atomic mass of this sample of bromine. Give your answer to one decimal place.

(3)

relative atomic mass = ..............................................................

ii) Give a reason why both isotopes of bromine have the same chemical properties.

(1)

A student investigates the reactivity of some halogens. She uses these solutions of halogens and their halides.

• bromine, chlorine and iodine

• sodium bromide, sodium chloride and sodium iodide

She adds each halogen solution to each halide solution. The table shows her results.

i) Explain how these results show the order of reactivity of bromine, chlorine and iodine.

(3)

ii) Suggest why the student does not need to add bromine solution to sodium bromide solution.

(1)

iii) The ionic equation for the reaction between bromine and sodium iodide is

Br₂ (aq) + 2I⁻ (aq) → I₂ (aq) + 2Br⁻ (aq)

Explain why this is a redox reaction.

(2)

The Group 7 elements are called halogens. Halogens form compounds called halides. Three of the halogens are represented by the formulae X₂ , Y₂ and Z₂ Solutions of these halogens are added separately to solutions of sodium halides, NaX, NaY and NaZ. The table shows whether or not a reaction occurs.

Use the information in the table to deduce the order of reactivity of the halogens X₂ , Y₂ and Z₂ 

most reactive ...................................           ....................................

least reactive ....................................

An aqueous solution of halogen Y₂ is orange. This solution is decolourised when it reacts with an alkene. Deduce the identity of halogen Y₂.

The table shows some physical properties of the halogens.

i) Complete the table by predicting a boiling point for chlorine, the state of fluorine at room temperature and the colour of astatine.

(3)

ii) Why do the halogens have similar chemical properties?

(1) 

A teacher uses this apparatus to demonstrate the reaction between chlorine gas and iron wool. The teacher does the reaction in a fume cupboard.

i) Suggest why the teacher does the reaction in a fume cupboard.

(1)

ii) The product of the reaction between iron and chlorine is iron(III) chloride. The ions in iron(III) chloride are Fe³⁺ and Cl⁻.

Use this information to give the chemical equation for this reaction.

(2)

This question is about elements in Group 7 and their compounds.

The table gives information about some of these elements.

 i) Predict the colour of fluorine at room temperature.

(1)

ii) How many of the elements in the table are liquids at room temperature (20 °C)?

(1)

iii) The element astatine is below iodine in Group 7. Predict the formula of a molecule of astatine.

(1)

Separate: Chemistry Only

 Sea water contains bromide ions.

Bromine can be obtained by bubbling chlorine through a sample of sea water.

The ionic equation for the reaction is

Cl₂ (g) + 2Br ^– (aq) → 2Cl^– (aq) + Br₂ (aq)

i) Explain which species acts as an oxidising agent in this reaction.

(2)

ii) The reaction occurs because chlorine is more reactive than bromine. Bromine is below chlorine in Group 7. Explain the decrease in reactivity from chlorine to bromine.

(3)

Elements in Group 7 react with elements in Group 1 to form ionic compounds.

Which pair of ions both have the electronic configuration 2.8.8?

The halogens are found in Group 7 of the Periodic Table.

Table 1 shows the melting point and boiling point of some of the halogens.

Table 1

What is the state of chlorine at -100 ^oC and at 0 ^oC?  State at -100 ^oC: ____________________ State at 0 ^oC: ____________________

Explain why the boiling point of the Group 7 elements increases as you go down the group as shown in Table 1.

The halogens all react with hydrogen to form the corresponding hydrogen halide. Explain why the halogens all react in a similar way.

Separate: Chemistry Only

Predict and explain the difference in the rate of the reaction between hydrogen with chlorine and between hydrogen and iodine.

Chorine is a halogen.

Chlorine reacts with aqueous potassium iodide to form aqueous potassium chloride and iodine.

i) Give the balanced symbol equation for this reaction.

(2)

ii) State what would be seen when this reaction occurs.

(1)

Separate: Chemistry Only

This reaction is a redox reaction. Explain, using half equations, what is being oxidised and what is being reduced.

Separate: Chemistry Only

Explain, in terms of their electronic configuration, why chlorine is more reactive than iodine.

Chlorine reacts with potassium to form the solid, potassium chloride. Write the balanced symbol equation for this reaction, including state symbols.