Chemistry core practical 4

Question 1

Aim

Answer 1

To investigate the relative rates of hydrolysis comparing chloroalkanes, bromoalkanes and iodoalkanes

Question 2

Step 1

Answer 2

Set up a water bath to 50°c

Question 3

Step 2

Answer 3

Fill 3 test tubes with 3cm of ethanol and 2 drops of halogenoalkane in each
Place bung on top loosely

Question 4

Step 3

Answer 4

Pour 5cm3 silver nitrate solution into 3 separate test tubes

Question 5

Step 4

Answer 5

Place all 6 test tubes into 50°c water bath and wait until it reaches 50°c

Question 6

Step 5

Answer 6

Add silver nitrate solution to one halogenoalkane and time how long it takes for a precipitate to be formed
Repeat for other halogenoalkanes

Question 7

Step 6

Answer 7

Repeat using 1-bromobutane, 2- bromobutane and 2-bromo-2-methylpropane instead of the other halogenoalkanes

Question 8

What precipitate is formed when adding silver nitrate?

Answer 8

A silver halide eg silver chloride
Which halogen had been substituted with OH from water to form this silver halide

Question 9

What is acting as the nucleophile (electron pair donor) to hydrolyse the halogenoalkanes?

Answer 9

Water in the silver nitrate solution
Substitutes halogen atom which reacts with the silver to form silver halide

Question 10

Why use ethanol?

Answer 10

To dissolve halogenoalkanes so they can react with water

Question 11

Why can water act as a nucleophile?

Answer 11

Contains a lone pair of electrons on oxygen a to be donated

Question 12

Why is water used as a nucleophile here and not hydroxide compound?

Answer 12

Because white precipitate formed instantly = not long enough to time

Question 13

What precipitate is formed fastest in terms of halogen atom?

Answer 13

Silver iodide because the carbon-iodine bond is the weakest due to longest bond length so faster rate of hydrolysis

Question 14

What precipitate is formed fastest in terms of primary, secondary, tertiary halogenoalkane?

Answer 14

Tertiary