Researching Chemistry

Question 1

What is recrystallisation?

Answer 1

A process used to purify solids

Question 2

What is an example of something that can be purified by recrystallisation?

Answer 2

Aspirin

Question 3

What are the required qualities for the solvent in a recrystallisation reaction ?

Answer 3

The solid must have a low solubility in the solvent at room temp or below but be readily soluble in the solvent at higher temperatures

Question 4

What is mixed melting point analysis ?

Answer 4

A process used to identify if a product is pure or not

Question 5

What is vacuum filtration ?

Answer 5

A filtration under reduced pressure that uses a Büchner funnel (lined with filter paper) and a vacuum flask.

Question 6

What is refluxing ?

Answer 6

A technique which allows substances to be heated for long periods of time without volition substances escaping

Question 7

What are essential to preventing accidents in refluxing?

Answer 7

Anti-bumping granules

Question 8

What is distillation ?

Answer 8

A process used to purify a liquid compound by heating away its impurities

Question 9

Which end does the water go IN in a reflux reaction ?

Answer 9

The bottom

Question 10

Which end does water do IN in a distillation reaction ?

Answer 10

At the top

Question 11

What can distillation be used for (besides separation) ?

Answer 11

Identifying compounds - but their boiling point

Question 12

What is solvent extraction ?

Answer 12

The process used to remove crude product from the reaction mixture

Question 13

How much crude product is left in the separation funnel after each solvent extraction ?

Answer 13

30%

Question 14

How does solvent extraction work ?

Answer 14

The crude product must be more soluble in the chosen solvent than in the reaction mixture. The solvent has to be immiscible in the reaction mixture thus creating two distinct layers. The layers are separated using a separation funnel

Question 15

What is gravimetric analysis?

Answer 15

A method of analysis for finding the mass of an element or substance in a compound.

Question 16

How does a gravimetric analysis experiment work ?

Answer 16

A substance of an unknown composition is forced to form a solid substance of known composition. It uses precipitation

Question 17

What are the essential qualities of a product of gravimetric analysis ?

Answer 17

A low solubility
A large particle size
Be a stable compound at temps between 100-110C

Question 18

What are back titrations used for ?

Answer 18

Finding the number of moles of a substance by reacting it with excess of a reactant of known concentration.
This mixture is then titrated to work out the number of moles used in the first reaction.

Question 19

When are titrations useful ?

Answer 19

When trying to work out the quantity of a substance with a low solubility

Question 20

What are Complexometric Titrations ?

Answer 20

Often to determine the concentration of metal ions present in a solution

Question 21

How do complexometric titrations work ?

Answer 21

Complexes are formed.

EDTA is often used - a ligand that binds in a 1:1 ratio with most metal ions

Question 22

What is a desiccator?

Answer 22

Sealed glass container used in gravimetric analysis