Group 7: the halogens

This question is about some Group 2 elements and their compounds.

Magnesium is reacted with titanium(IV) chloride to extract titanium metal.

Give the equation for this reaction.

State the role of magnesium in this reaction.

Equation

Role of magnesium

Complete Table 1 by giving the formula of a suitable calcium compound for each use.

Magnesium hydroxide is used to relieve the symptoms of indigestion by neutralising stomach acid.

Suggest why magnesium hydroxide is safer than sodium hydroxide as a treatment for indigestion.

An ionic compound of a Group 2 element dissolves in water to form solution X.

Separate samples of solution X are tested to identify the ions.

Table 2 shows the observations.

Identify the Group 2 cation in solution X.

Give an ionic equation for the reaction that occurs in Test 1.

Ionic equation

Identify the anion in solution X.

Give an ionic equation, including state symbols, for the reaction that occurs in Test 2

Explain why AgNO₃(aq) is acidified.

Ionic equation

Give one property of barium sulfate that makes it useful in hospitals.

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

Explain why chlorine has a lower boiling point than bromine.

Bromine reacts with fluorine to form BrF₃

Determine the oxidation state of bromine and of fluorine in BrF₃

Draw the shape of a BrF₃ molecule.

Include any lone pairs of electrons that influence the shape.

Explain why the BrF₃ molecule has the shape you have drawn.

Shape

Explanation of shape

Solid sodium bromide reacts with concentrated sulfuric acid.

Two reactions occur

• an acid-base reaction

• a redox reaction.

Give an equation and an observation for each reaction.

Equation for acid-base reaction

Observation for acid-base reaction

Equation for redox reaction

Observation for redox reaction

Iodide ions reduce copper(II) ions in aqueous solution to form a precipitate of copper(I) iodide.

Give an equation for this redox reaction.

This question is about chlorine.

Give an equation to show how chlorine forms an acidic solution in water.

Give an equation for the reaction between chlorine and cold, dilute aqueous sodium hydroxide.

In acidic conditions, ClO₃^– ions oxidise Cl^– ions to form Cl₂

Deduce a half-equation for the oxidation of Cl^– to Cl₂

Deduce a half-equation for the reduction of ClO₃^– to Cl₂

Deduce the overall equation for this reaction.

Half-equation for the oxidation of Cl^– to Cl₂

Half-equation for the reduction of ClO₃^– to Cl₂

Overall equation

Give the equation for the reaction of solid sodium chloride with concentrated sulfuric acid.

State the role of the chloride ions in this reaction.

Equation

Draw the shape of the Cl₃^– ion. Include any lone pairs of electrons that influence the shape.

Chlorine forms an ion with the Group 3 element thallium (T l).

State and explain the bond angle in TlCl₂⁺

Which statement correctly describes a trend down Group 7 from C l to I ?

X represents C l, Br or I

Which statement about chloride ions is correct?

A student is given two aqueous solutions, L and M, that both contain iron salts.

The student does a series of tests on the solutions.

Table 1 shows these tests and the observations.

Identify L and M using the results in Table 1.

In your answer:

• identify all precipitates

• explain why effervescence is seen in the reaction of sodium carbonate with L but not with M

• give ionic equations for all reactions.

Which species is the strongest reducing agent?

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

Chlorine is added to some drinking water supplies to decrease the risk of people suffering from diseases such as cholera.

State why the amount of chlorine added must be controlled.

Give an equation for the reaction of chlorine with water to form a solution containing two acids.

Explain, with reference to electrons, why this is a redox reaction.

Equation

A student bubbles chlorine gas through a solution of sodium iodide.

State the observation the student would make.

Give an ionic equation for the reaction.

Ionic equation

The student adds a few drops of concentrated sulfuric acid to a small amount of solid sodium iodide.

Two gaseous sulfur-containing products are formed.

Give an equation for the formation of each of these sulfur-containing products.

State the role of sulfuric acid in the formation of these products.

Equation 1

Equation 2

The student adds a few drops of acidified silver nitrate solution to a solution of an unknown impure sodium halide. The student observes bubbles of gas and a colourless solution. The student bubbles the gas through calcium hydroxide solution and a white precipitate forms.

Deduce the identity of the sodium halide.

Suggest the identity of the gas.

Give an ionic equation for the formation of this gas from the impurity.

Identity of sodium halide

Ionic equation

The ClF₂⁺ ion contains two different Group 7 elements.

Use your understanding of the electron pair repulsion theory to draw the shape of this ion.

Include any lone pairs of electrons that influence the shape.

Explain why the ion has the shape you have drawn.

Suggest a value for the bond angle in the ion.

Shape

Magnesium is used in the extraction of titanium from titanium(IV) chloride.

Give an equation for this reaction.

A test for chloride ions in aqueous solution involves adding dilute nitric acid followed by aqueous silver nitrate.

What is the reason for adding the nitric acid?

This question is about Group 7 chemistry.

Give an equation for the reaction of solid sodium bromide with concentrated sulfuric acid to form bromine.

State one observation made during this reaction.

Equation

A solution that is thought to contain chloride ions and iodide ions is tested.

1. Dilute nitric acid is added to the solution.

2. Aqueous silver nitrate is added to the solution.

3. A pale yellow precipitate forms.

4. Excess dilute aqueous ammonia is added to the mixture.

5. Some of the precipitate dissolves and a darker yellow precipitate remains.

Give a reason for the use of each reagent.

Explain the observations.

Give ionic equations for any reactions.

Which statement about chloride ions is not correct?

Which compound forms a white precipitate when added to aqueous silver nitrate?

This question is about sodium halides.

State what is observed when silver nitrate solution is added to sodium fluoride solution.

State one observation when solid sodium chloride reacts with concentrated sulfuric acid.

Give an equation for the reaction.

State the role of the chloride ions in the reaction.

Equation

Give an equation for the redox reaction between solid sodium bromide and concentrated sulfuric acid.

Explain, using oxidation states, why this is a redox reaction.

Equation

State what is observed when aqueous chlorine is added to sodium bromide solution.

Give an ionic equation for the reaction.

Ionic equation

In the test for a halide ion in aqueous solution, dilute nitric acid is added before the addition of silver nitrate solution.

Why is nitric acid added?

This question is about some Group 7 compounds.

Solid sodium chloride reacts with concentrated sulfuric acid.

Give an equation for this reaction. State the role of the sulfuric acid in this reaction.

Equation

Fumes of sulfur dioxide are formed when sodium bromide reacts with concentrated sulfuric acid.

For this reaction

• give an equation

• give one other observation

• state the role of the sulfuric acid.

Equation

Chlorine reacts with hot aqueous sodium hydroxide as shown in the equation.

3Cl₂ + 6NaOH → NaClO₃ + 5NaCl + 3H₂O

Give the oxidation state of chlorine in NaClO₃ and in NaCl

State, in terms of redox, what happens to chlorine in the reaction in Question 05.3.

Solution Y contains two different negative ions.

To a sample of solution Y in a test tube a student adds

• silver nitrate solution

• then an excess of dilute nitric acid

• finally an excess of concentrated ammonia solution.

The observations after each addition are recorded in Table 3.

Give an equation to show the conversion of D into G.

Ionic equation to form E

Equation to show the conversion of D into G

An aqueous solution of a salt gives a white precipitate when mixed with aqueous silver nitrate and when mixed with dilute sulfuric acid.

Which could be the formula of the salt?

Which statement is not correct about the trends in properties of the hydrogen halides from HC l to HI ?