Practicals- Please Do Well

Question 1

Preparing standard solution

Answer 1

• weigh solid
• dissolve solid in a beaker using distilled water
• transfer to volumetric flask
• rinse flask
• fill up to 250cm^3
• invert several times

Question 2

Explain the effect of the flask is filled with water above the graduation line

Answer 2

Titre would be less as solution is more dilute

Question 3

Explain what would happen if you did not invert the flask

Answer 3

Solution used in the 1st titre would be more dilute than solution used later
1st titre would need less solution

Question 4

Carrying out a titration

Answer 4

• add measured volume of one solution using a pipette into a conical flask
• add other solution to burette, record reading
• add indicator to flask
• add solution from burette
• with swirling
• stop at end point
• repeat

Question 5

Preparing a liquid product

Answer 5

• use of a separating funnel to remove an organic layer from an aqueous layer
• drying with an anhydrous salt (e.g. MgSO4, CaCl 2)
• redistillation

Question 6

Filtration under reduced pressure apparatus

Answer 6

• buchner flask
• buchner funnel
• pressure tubing
• filter paper
• vaccum

Question 7

Filtration under reduced pressure

Answer 7

• ensure good seal of flask and funnel by adding pressure to it
• place filter paper and wet it
• filter the sample
• rise beaker

Question 8

Why is it important to heat the sample slowly when carrying out a melting point determination

Answer 8

• Sample melts over a range of temp

- heating too quickly will result i the thermometer recording a higher temp than actual range

Question 9

What effect would not cooling the mixture after recrystallisation have on the final yield?

Answer 9

• some of the solid will still be dissolved in the solvent and so not all the solid will have crystallised
• yield would be lower because of the solid is still dissolved in the solvent

Question 10

What does Rf stand for?

Answer 10

Retention factor

Question 11

How to calculate Rf

Answer 11

Distance moved by the compound/ distance moved by the solvent front

Question 12

What does TLC indicate?

Answer 12

How many compounds are in a mixture

Question 13

Identify carboxylic acid

Answer 13

Add aqueous sodium carbonate

Effervescence