A-Level AQA Chemistry: Group 2 and Group 7

How does the trend in electronegativity change in group 7, from fluorine to iodine?

The atoms become less electronegative as you go down the group

Why is there a decrease in electronegativity as you go down group 7?

1) Atomic radius increases 2) More inner shell electrons so more shielding. These factors mean there is less attraction between the shared electrons in the covalent bond, and the nucleus.

How does the trend in boiling point change as you go down group 7?

The boiling points increase

Why is there an increase in boiling point as you go down group 7?

The molecules get larger down the group, as there is an increase in the number of inner electron shells. Van der Waals forces are stronger with larger molecules, so they require more energy to overcome.

What two chemicals are used to make bleach? What 3 products are produced from the reactions between these?

Chlorine and sodium hydroxide. Sodium chlorate, sodium chloride and water

Give 3 uses of chlorine in water.

1) it kills disease causing micro organisms. 2) some of the chlorine remains and prevents re-infection. 3) it prevents algae from growing = no bad smells, tastes or discolouration

Is chlorine's reaction with cold water a reversible or irreversible reaction?

Reversible

Give the balanced equation for chlorine's reaction with cold water.

Cl2 + H20 to HClO and HCl

What is the formula for chloric acid and how does it kill bacteria?

Chloric acid (HClO) is an oxidising agent and kills bacteria by oxidation

What is the name of the reaction that occurs when chlorine reacts with sunlight?

A photochemical reaction

Give the balanced equation of the reaction between water and chlorine in sunlight.

2H2O + 2Cl2 to 4HCl + O2

Is the photochemical between chlorine and water reversible or irreversible?

It is an irreversible reaction.

What type of reaction is the reaction between cold water and chlorine (answer is not reversible)?

Disproportionation

What is the word equation of chlorine and another product to make bleach?

Chlorine + sodium hydroxide to Sodium chlorate, salt and water

What is the balanced eqauation of chlorine and sodium hydroxide to make bleach?

Cl2 + 2NaOH to NaCl + NaClO + H2O

Give the balanced equation for the reaction between sodium chloride and sulfuric acid.

NaCl + H2SO4 to NaHSO4 + HCl

What type of reaction is the reaction between sulfuric acid and sodium chloride to form hydrochloric acid and sodium hydrogen sulfate?

Acid-base reaction

Give the balanced equation for the acid base reaction between sodium bromide and sulfuric acid.

NaBr + H2SO4 to NaHSO4 + HBr

Why does a further reaction occur when bromide ions react with sulfuric acid, but not when chloride or fluoride ions do?

Bromide is a better reducing agent, because its atomic radius is bigger and it has an extra filled inner shell of electrons. This means it can reduce other atoms more easily because there is less attraction between the outer shell electrons and the nucleus.