Group 7 Flashcards by Hannah Alam

What are the physical properties for F2, Cl2 , Br2 and I2?

F2= pale yellow gas
Cl2= Green/yellow gas
Br2=Orange/ brown liquid
I2= Grey/black solid and purple vapour

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What is the pattern in atomic radius down the group?

The atomic radius increases down the group

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What is the pattern in electronegativity down the group?

Electronegativity decreases down the group as there is a larger atomic radius because there is more shielding so the attraction of the outer shell electron and the positive nucleus is less.

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What is the pattern in melting and boiling point down group 7?

It increases down the group as the atomic radius increases and there are more electrons. Therefore there is stronger van Der Waals forces.

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What do you identify metal halides (except fluorine) with?

Silver ions

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What does AgCl form ?

White precipitate

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What does AgBr form?

Cream precipitate

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What does AgI form?

Yellow precipitate

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Describe the procedure of identifying metal halides with silver ions?

Step 1:
- Add dilute nitric acid HNO3 to halide solution , this gets rid of any soluble carbonate or hydroxide impurities. If C03^2- is present it would interfere with the test by forming silver carbonate or insoluble silver hydroxide.
Step 2 :
- Add a few drops of silver nitrate solution and you will observe the precipitates formed. However distinguishing between the precipitates can be quite difficult so dilute and concentrated ammonia can help with this.

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What do Oxidising agents do?

They take electrons (OAT)

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What do Reducing agents do?

They donate electrons (RAD)

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Are Halogens oxidising or reducing agents?

Oxidising

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What is the pattern of oxidising ability down group 7 and why?

The oxidising ability of the halogens decrease down the group because down the group it becomes harder to gain and electron because the atoms have a larger atomic and there is more shielding

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If the oxidation state of an element increases is it oxidation or reduction?

Oxidation

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If the oxidation state of an element decreases is it oxidation or reduction?

Reduction

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Write the equation for the reaction of Sodium Chloride reacting with Sulfuric acid.

NaCl + H2SO4 —> NaHSO4 + HCl

What type of reaction is Sodium chloride reacting with Sulfuric acid and what are the observations?

Acid-base and steamy fumes

Write the equation for the reaction of Sodium Bromide and Sulfuric acid to form Hydrogen Bromide.

NaBr + H2SO4 —-> NaHSO4 + HBr

What type of reaction is Sodium Bromide reacting with Sulfuric acid and what are the observations?

Acid- base and steamy fumes

Write the equation for the reaction between Bromide ions and sulfuric acid.

2Br- + H2SO4 + 2H+ —> Br2 + SO2 + H20

What type of reactions are happening between bromide ions and sulfuric acid and what are the observations?

Oxidation of Bromide - Brown fumes
Reduction of H2SO4 - Colourless gas

Write the equation for reaction between NaI and H2SO4.

NaI + H2SO4 —> NaHSO4 + HI

What type of reaction is Sodium Iodide with Sulfuric acid and what are the observations?

Acid base and steamy fumes

Write the ionic equation between Iodide ions and Sulfuric acid to form I2 and SO2.

2I- + H2SO4 + 2H+ –> I2 + SO2 +2H20

What type of reaction is Iodide ions reacting with Sulfuric acid and what are the observations?

Oxidation of Iodide ions - purple fumes Reduction of H2SO4 - Colourless gas

Write the equation of the reaction between Iodide ions sulfuric acid and hydrogen ions to create S and what are the observations. What type of reaction is this?

6I- + H2SO4 + 6H+ --> 3I2 + S + 4H20 Yellow solid formed Reduction of H2SO4

Write the equation of the reaction between iodide ions , sulfuric acid and hydrogen ions to form H2S and what are the observations. What type of reaction is this?

8I- + H2SO4 + 8H+ ---> 4I2 + H2S + 4H20 Gas (bad egg smell) Reduction of H2SO4

What is the reducing power trend down group 7?

Down the group it becomes easier to lose an electron because ions become larger and there is more shielding therefore the reducing power increases down the group

What are the sources of Bromine?

- Sea water contains small amounts of Bromide ions that can be oxidised by chlorine to give bromine

What are the sources of Iodine?

- Salts such as NaCl , KCl and K2SO4 are removed from kelp by washing , the residue is heated with manganese dioxide and concentrated sulfuric acid.

What is the equation for Iodide ions reacting with Manganese Dioxide and sulfuric acid.?

2I- + MNO2 + 4H+ --> Mn2+ + I2 + 2H20

What is one use of chlorine? (write as many notes as possible)

Reaction with water: - A reversible reaction occurs to form chloric acid and hydrochloric acid Cl2(g) + H20(l) ⇌ HCLO(aq) + HCL(aq) - The oxidation number of one Cl atom increases and the oxidation number of the other decreases , this is called disproportionation. - This reaction takes place when water is purified for drinking water and in swimming pools. Reaction with water and sunlight: - In sunlight a different reaction occurs 2Cl2(g) + 2H20(l) ---> 4HCl(aq) + 02(g) - Because of this chlorine is rarely lost from pools and needs chlorine added frequently Chlorination: -We can also add sodium or calcium chlorite NaClO(s) + H20(l) ⇌ Na+(aq) + OH-(aq) + HClO(AQ) - Sodium Chlorate dissolves in water to give chloric acid and in alkali conditions the equilibrium shifts to the left and removes HClO so pools must be kept slightly acidic using this method. Reaction with Alkali: Reactants- Chlorine and Sodium Hydroxide Conditions- NaOH must be cold and dilute Cl2(g) + 2NaOH(aq) ---> NaClO(aq) + NaCl(aq) + H20(l) Products- Sodium Chlorate , Sodium Chloride and water This is another disproportional reaction , sodium chlorate is an oxidising agent and an active ingredient in bleach