Repeated Mistakes

Question 1

What would speed up the reaction between a halogen alkane and aqueous potassium hydroxide?

Answer 1

Sodium hydroxide

The hydroxide group is a stronger nucleophile

Question 2

Why can ketones dissolve in a wide range of substances?

Answer 2

They have polar and nonpolar characteristics

Question 3

Explain the role of water in the reaction between a halogen alkane and alcoholic potassium hydroxide

Answer 3

Elimination reaction

The hydroxide from the water act as a base by accepting a proton rather than as a nucleophile

Question 4

Suggest a suitable drying agent to absorb the water remaining in the ethanol of the distillation

Answer 4

Anhydrous magnesium sulphate

Add to ethanol, leave then decant

Question 5

Why is it dangerous to have a sealed apparatus when a gas is being produced?

Answer 5

Buildup of pressure

Question 6

Why do you primary halogenoalkanes react with water via a different mechanism than that secondary or tertiary?

Answer 6

Primary carbocations ions are less stable

Question 7

What with different when potassium bromide reacts with concentrated sulphuric acid compare to potassium iodide? Observations

Answer 7

Black / (shiny) grey solid (1)
Purple / violet / pink vapour / fumes (1)
Smell of (bad) eggs (1)
Yellow solid (1)

Question 8

By considering the hydrogen bonding on water and ethanol, suggest why 2–chlorobutane is more soluble in ethanol than in the water

Answer 8

Water has 2 hydrogen bonds per molecule (on average) whereas ethanol only has 1 (1)
Needs more energy to break H bonds in water (so less soluble) / H bonding (ALLOW intermolecular forces) stronger in water (1)

Question 9

How would a more dilutes solution of sodium thiosulphate affect the accuracy of the results?

Answer 9

Larger titration reading (1)
So smaller (%)error in titration reading (1)

Question 10

How would you using less iodine affect the accuracy of the titration results?

Answer 10

Smaller titration reading as more I2 reacts/ less I2 left (1)
So greater (%) error in titration reading (1)

Question 11

What is essential if the species is to act as a nucleophile?

Answer 11

A lone pair of electrons

Question 12

What is the colour change of phenolphthalein indicator?

Answer 12

Colourless in alkali solution

To pink

Question 13

What is the organic product of the reaction between chloroethane and sodium hydroxide?

Answer 13

Alcohol

Question 14

What is the mechanism and type of reaction between aqueous sodium hydroxide and a halogenoalkane?

Answer 14

Nucleophilic substitution

Question 15

What could the reaction between an alkene and hydrogen in the presence of a nickel catalyst be classed as?

Answer 15

Addition and reduction

Question 16

What reagents and conditions are needed to convert 1-bromobutane into butan-1-ol?

Answer 16

Sodium hydroxide

Heat in aqueous solution in mixture of water and ethanol

Question 17

What reagents and conditions are needed to convert 1-iodobutane into butylamine?

Answer 17

Ammonia in ethanol

Heat and pressure

Question 18

What really didn’t think conditions are needed to convert 2-chloropropane into propene?

Answer 18

Sodium hydroxide

Heat and dissolved in ethanol

Question 19

Chloroethane can be prepared by reacting at the know with potassium chloride in the presence of concentrated sulphuric acid. Explain why a similar reaction using potassium iodide and concentrated sulphuric acid should not be used to prepare idoethane

Answer 19

Sulphuric acid is a strong enough oxidising agent

To oxidise iodide ions

Question 20

Why are some CFCs used as fire retardants?

Answer 20

Absorb heat from fire
Prevent oxygen from reaching fire
Absorb free radicals in combustion propagation
Strength of C-F bonds make them inert