Group 7: the halogens

The elements in group 7 of the periodic table are called the halogens.

Give the symbol of the element astatine.

Use the periodic table to help you.

What is the colour of chlorine gas at room temperature?

Damp blue litmus paper can be used to test for chlorine gas.

Use words from the box to complete the sentences.

When damp blue litmus paper is added to chlorine gas there are two colour changes.

The damp blue litmus paper changes from blue to_........ .

The colour of the litmus paper then changes to_........ .

Figure 1 shows the atomic number and boiling point of some of the halogens.

Describe the trend in the boiling points of the first three halogens in Figure 1.

Using the information in Figure 1, predict the boiling point of iodine.

Write your prediction on the answer line below.

This question is about molecules containing two atoms.

In an experiment, hydrochloric acid is reacted with zinc.

The volume of gas produced is measured by collecting the gas in an upturned measuring cylinder over water.

Give a method of collecting and measuring the gas that would give a more accurate volume of gas.

Iodine has an atomic number of 53 and a mass number of 127.

How many electrons are there in an iodine molecule, I₂?

Iodine reacts with hydrogen to form hydrogen iodide, H I.

Explain whether or not a solution of hydrogen iodide in water conducts electricity.

Chlorine gas is bubbled through a colourless solution of potassium bromide, KBr. The mixture turns orange.

Give the name of the substance that causes the orange colour.

Write the balanced equation for this reaction.

Hydrogen iodide reacts with oxygen to form water and iodine.

The equation for this reaction is

Calculate the energy change for this reaction using the bond energies in Figure 11.

Include a sign and unit in your answer.

This question is about bromine.

Give the colour and physical state of bromine at room temperature.

Bromine reacts with hydrogen to form hydrogen bromide.

Write the word equation for this reaction.

Hydrogen bromide dissolves in water to form a solution.

This solution of hydrogen bromide reacts with alkalis.

State the type of reaction that occurs when a solution of hydrogen bromide reacts with an alkali.

Bromine and the other halogens react with hot iron wool.

Figure 11 shows the relative speed of some of these reactions.

Fluorine also reacts with hot iron wool.

Use Figure 11 to predict the relative speed of this reaction.

Potassium bromide contains 32.8% potassium by mass.

Calculate the mass of potassium and the mass of bromine in 500 g potassium bromide.

The elements in group 7 of the periodic table are the halogens.

Which row shows the colour and physical state of iodine at room temperature?

Iron wool is heated with bromine vapour as shown in Figure 12.

At the end of the reaction, a solid forms at the top of the test tube.

Identify the solid.

Aluminium reacts with bromine.

Write the balanced equation for the reaction between aluminium and bromine.

*(d) (i) The order of reactivity of the halogens can be found by displacement reactions.

A student was provided with

• solutions of bromine, chlorine and iodine

• solutions of sodium bromide, sodium chloride and sodium iodide.

Describe experiments the student could carry out using these solutions to find the order of reactivity of bromine, chlorine and iodine, explaining how the results would show the order of reactivity.

You should use equations to support your answer.

Explain why the displacement reactions of halogens are redox reactions.

Figure 6 shows some information about the group 1 metals.

Explain, in terms of their electronic configurations, why these metals are placed in group 1 of the periodic table.

Which row shows two correct properties of group 1 metals?

The word equation for the reaction of potassium with bromine is

potassium + bromine potassium bromide

Add the missing state symbol and balance the equation for this reaction.

A sample of potassium contains three isotopes, potassium-39, potassium-40 and potassium-41.

Explain the meaning of the term isotopes.

This sample of potassium contains

93.25% potassium-39

0.02% potassium-40

6.73% potassium-41

Calculate the relative atomic mass of this sample of potassium.

Chlorine gas can be prepared by reacting concentrated hydrochloric acid with solid potassium manganate(VII).

Figure 10 shows the apparatus used.

Figure 11 shows the hazard symbols for concentrated hydrochloric acid, potassium manganate(VII) and chlorine gas.

Use the information in Figure 11 to help you answer (a)(i) and (a)(ii).

What are the hazards associated with potassium manganate(VII)?

Explain one precaution that should be taken when preparing the sample of chlorine gas.

precaution

reason

State the purpose of the delivery tube.

Suggest why damp blue litmus is placed at the top of the gas jar.

In the reaction, potassium manganate(VII), KMnO₄, reacts with hydrochloric acid to form manganese chloride, MnCl₂, potassium chloride, chlorine and water.

Write the balanced equation for the reaction.

This question is about elements in group 7, the halogens.

Which halogen is a green gas at room temperature and pressure?

Bromine, chlorine and iodine all react with heated iron wool.

Figure 9 shows the speed of these reactions.

When iron wool is heated with chlorine, iron chloride is formed.

Write the word equation for this reaction.

Give the name of the halogen in Figure 9 that is the most reactive with iron.

34.4 % of the mass of iron chloride is iron.

Calculate the mass of iron and the mass of chlorine in 125 g of iron chloride.

Alkenes react with halogens.

When iron chloride is added to the reaction mixture, the reaction is much faster but the products are the same.

Use words from the box to complete the sentences.

The iron chloride speeds up the reaction because it is_........

After the reaction, the mass of iron chloride is_........

The elements in group 7 of the periodic table are known as the halogens.

Name the halogen that is in period 4 of the periodic table.

Explain why chlorine is more reactive than iodine.

A piece of burning sodium is placed into a gas jar containing chlorine gas, as shown in Figure 9.

At the end of the reaction, the inside of the gas jar is coated with white crystals.

Identify the white crystals.

Sodium also reacts with bromine.

Write the balanced equation for the reaction between sodium and bromine.

In another experiment, a student adds colourless sodium bromide solution to chlorine water.

State what you would see in this reaction.

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

Explain which species has been oxidised in this reaction.

Fluorine, chlorine, bromine and iodine are elements in group 7 of the periodic table.

State the name given to the group 7 elements.

Name one other element that is in group 7. Use the periodic table on the back of this exam paper to help you.

Which element is liquid at room temperature and pressure?

Which element is dark-grey in colour at room temperature and pressure?

Tin reacts with chlorine to form tin chloride. A sample of tin chloride contains 1.19 g of tin and 1.42 g of chlorine.

Calculate the empirical formula of this tin chloride.

(relative atomic masses: C l = 35.5, Sn = 119.0)

You must show your working.

empirical formula of this tin chloride =_........

Tin also reacts with fluorine. The reaction between fluorine and tin is much more vigorous than the reaction between chlorine and tin.

Figure 8 shows the electronic configurations of fluorine and chlorine.

Explain, in terms of their electronic configurations, why fluorine reacts with tin more vigorously than chlorine reacts with tin.

This question is about some of the elements in group 7 of the periodic table.

Which row in the table correctly shows the colours and physical states of the elements at room temperature?

The compound phosphorus oxychloride has the formula POCl₃.

Calculate the percentage by mass of chlorine in phosphorus oxychloride.

(relative atomic masses: O = 16.0, P = 31.0, C l = 35.5)

percentage by mass of chlorine =_........

When iron reacts with chlorine, iron chloride is formed.

Two possible equations for this reaction are

A Fe + Cl₂ FeCl₂ B 2Fe + 3Cl₂ 2FeCl₃

In an experiment, 8.40 g iron reacts with chlorine to form 19.05 g iron chloride.

Show, using a calculation, which reaction, A or B, is taking place.

You must show your working.

(relative atomic masses: C l = 35.5, Fe = 56.0)

*(d) Group 1 metals react with the elements from group 7 to form salts.

Some examples of these reactions are shown in Figure 10.

You will find the position of these elements in their groups on the periodic table.

Explain, in terms of their electronic configurations and the relative reactivity of these elements, which of the reactions shown in Figure 10 would be the most violent.

Chlorine, bromine and iodine are elements in group 7 of the periodic table.

Chlorine is toxic.

State one safety precaution that should be taken when using chlorine in the laboratory.

Chlorine reacts with hydrogen to form hydrogen chloride.

Write the word equation for this reaction.

Hydrogen chloride dissolves in water to form an acidic solution.

State what is seen when blue litmus paper is placed into this solution.

A chlorine atom has seven electrons in its outer shell. A hydrogen atom has one electron in its outer shell.

Complete the dot and cross diagram of a molecule of hydrogen chloride. Show outer shell electrons only.

Name the type of bonding in a molecule of hydrogen chloride.

If chlorine solution is added to sodium bromide solution a reaction occurs.

chlorine + sodium bromide sodium chloride + bromine

Give a reason why this reaction occurs.

Figure 8 shows apparatus used to find out if a solution conducts electricity.

Glucose solution and sodium chloride solution are tested. Glucose is a typical simple molecular covalent compound. Sodium chloride is an ionic compound.

State what would happen to the lamp when glucose solution is tested.

State what would happen to the lamp when sodium chloride solution is tested.

Figure 9 shows how the conductivity of one solution changes as its concentration increases.

Figure 9

Describe how the conductivity of this solution changes as its concentration increases from 0 to 500 g dm^–3.

An atom of potassium has atomic number 19 and mass number 39.

Give the electronic configuration of this potassium atom.

This potassium atom forms the ion K⁺.

Which row shows the number of protons and the number of neutrons in this potassium ion, K⁺?

Potassium and caesium are in the same group of the periodic table.

Explain, in terms of electrons, why potassium and caesium are in the same group.

Fluorine boils at –188C. There are forces between fluorine molecules.

Explain, in terms of these forces, why the boiling point of fluorine is low.

Potassium reacts with fluorine to form potassium fluoride. Potassium fluoride is a solid.

Complete the balanced equation for this reaction and add the state symbols.

What are the elements in group 1 of the periodic table called?

Figure 14 shows the melting points and boiling points of elements in group 7 of the periodic table.

Give, using Figure 14, the boiling point of bromine.

State which two elements from Figure 14 are solids at room temperature.

Sodium thiosulfate solution, Na₂S₂O₃, reacts with dilute hydrochloric acid.

When dilute hydrochloric acid is mixed with sodium thiosulfate solution, the mixture turns cloudy.

Explain why the mixture turns cloudy.

In an investigation, different concentrations of hydrochloric acid are reacted with sodium thiosulfate solution. The mixture goes cloudy at different rates.

Describe how the rate at which the mixture goes cloudy can be measured.

You are provided with some dilute hydrochloric acid which has a concentration of 50 g dm^–3.

For this experiment, dilute hydrochloric acid with a concentration of 20 g dm^–3 is required.

How much water must be added to 100 cm³ of 50 g dm^–3 hydrochloric acid to make dilute hydrochloric acid with a concentration of 20 g dm^–3?

Sodium iodide solution is colourless.

When a solution of bromine is added to sodium iodide solution, a reaction occurs.

The mixture turns brown.

Give the name of the substance causing the brown colour.

Explain which substance has been reduced in this reaction.

Complete the following sentences.

The name given to group 7 in the periodic table is_........ .

The name given to group 0 in the periodic table is_........ .

Which of the following rows gives the colours of the group 7 elements chlorine and bromine at room temperature?

Figure 2 shows the melting and boiling points of bromine and iodine.

element	melting point in C	boiling point in C
bromine	–7	59
iodine	114	184

Using the information in Figure 2, which row shows the physical states of these elements at 50C?

The densities of some elements in group 0 are shown in Figure 3.

Use the information in Figure 3 to suggest the density of krypton.

For many years, argon was used to fill filament light bulbs.

A filament light bulb is shown in Figure 4.

When the bulb is in use the metal filament becomes extremely hot.

Explain why argon, rather than air, was used to fill filament light bulbs.

Fluorine, chlorine, bromine, iodine and astatine are elements in group 7.

Describe the test to show that a gas is chlorine.

Bromine reacts with hydrogen to form hydrogen bromide. Hydrogen bromide dissolves in water to form a solution.

State the name of the solution formed.

There is a trend in the colour and the state of the halogens at room temperature.

Predict the colour and state of astatine at room temperature.

Bromine, chlorine and iodine are dissolved in water to make aqueous solutions. Potassium iodide solution is added to each of these solutions.

Figure 6 shows the observations.

Explain the observations shown in the table.

Fluorine reacts vigorously with iron to produce iron(III) fluoride, FeF₃.

Write the balanced equation for this reaction.

(a) A chlorine atom contains 17 electrons, 18 neutrons and 17 protons.

State the mass number of this chlorine atom.

Give the electronic configuration of this chlorine atom.

Describe what you would see if damp, blue litmus paper is placed into chlorine gas.

Chlorine exists as diatomic molecules.

In a molecule, two chlorine atoms are joined by a covalent bond.

Describe what is meant by a covalent bond.

Explain why chlorine is a gas, rather than a liquid, at room temperature.

When the gas hydrogen chloride, HC l, is dissolved in water, a solution forms. Blue litmus paper dipped in this solution turns red.

State why the litmus paper turns red.

Figure 13 lists the halogens in the order in which they appear in group 7 of the periodic table.

The melting points of four of the halogens are given.

Estimate the melting point of iodine.

Bromine reacts with heated iron.

Give the name of one halogen that would react with iron more vigorously than bromine.

(a) A chlorine atom contains 17 electrons, 18 neutrons and 17 protons.

State the mass number of this chlorine atom.

Give the electronic configuration of this chlorine atom.

Describe what you would see if damp, blue litmus paper is placed into chlorine gas.

Chlorine exists as diatomic molecules.

In a molecule, two chlorine atoms are joined by a covalent bond.

Describe what is meant by a covalent bond.

Explain why chlorine is a gas, rather than a liquid, at room temperature.

When the gas hydrogen chloride, HC l, is dissolved in water, a solution forms. Blue litmus paper dipped in this solution turns red.

State why the litmus paper turns red.

Describe what is seen when chlorine water is added to potassium bromide solution and the mixture shaken.

Chlorine reacts with potassium bromide to form potassium chloride and bromine. In this reaction chlorine forms chloride ions

In this reaction, chlorine has been reduced.

Explain, using the equation, how you know that chlorine has been reduced.

Write the half equation for the formation of bromine from bromide ions.

Aluminium reacts with chlorine to form aluminium chloride.

Write the balanced equation for this reaction.

A solid ionic compound is dissolved in water to form a solution.

Describe a simple experiment to show that charged particles are present in this solution.