(U3) Practicals

Question 1

Give the colour changes for Phenolphthalein and Methyl Orange

Answer 1

1. phenolphthalein :

• colourless in acid.
• pink in alkali solutions.
• colourless in neutral solutions

2. methyl orange :

• red in acid.
• yellow in alkali solutions.
• yellow in neutral solutions

Question 2

During any titrations, how do you ensure all chemicals are transferred between apparatus?

(2)

Answer 2

• Rinse apparatus with deionised water in a wash bottle
• transfer washings into the appropriate container

Question 3

what is a standard solution?

Answer 3

solution of a known concentration

Question 4

Describe how you can use test tube reaction to distinguish between butan-2-ol and 2-methylpropan-2-ol.

Include reagents, conditions, observations & explain chemistry involved.

Answer 4

• add acidified potassium dirchromate —> acidified in H₂SO₄ —> heat with sample
• butan-2-ol is secondary, 2-methylpropan-2-ol is tertiary
• butan-2-ol turns green from orange, 2-methylpropan-2-ol won’t
• 2-methylpropan-2-ol is tertiary and the intermediate carbocation is too stable to react
• butan-2-ol is secondary and is therefore less stable
• further oxides to a ketone

Question 5

Describe the process used to prepare a halogenoalkane (11)

Answer 5

• dissolve NaBr in water in a conical flask
• add butan-1-ol to the solution
• add conc H₂SO₄ to the solution while stirring
• add anti-bumping granules to the flask for smooth boiling
• set up reflux condenser & heat the mixture e.g for 5 mins to allow the reaction to proceed
• after refluxing, rearrange the apparatus for distillation
• distill the mixture and collect the fraction that boils at b.p. of 1-bromobutane
• transfer to a separating funnel
• wash organic layer with water to remove impurities
• dry the organic layer with an anhydrous salt
• perform a final distillation to obtain pure 1-bromobutane

Question 6

How do you release pressure in a separating funnel? (4)

Answer 6

• stopper the funnel and hold it upside down with the tap closed
• point the tap away from yourself and others
• open the tap slowly
• close the tap and turn the funnel upright again, shake gently if needed

Question 7

What 3 essential pieces of apparatus are needed for determining temperature increase of water by burning a fuel?

Answer 7

• thermometer
• spirit burner
• calorimeter / copper can