C10

Question 1

Purity

Answer 1

A pure substance is one that is made up of just one substance. That substance can be either an element or compound

Question 2

What is purity not?

Answer 2

-Its not referring to chemical purity

-e.g. orange juice advertised as pure

Question 3

What are the fixed points of an element or compound?

Answer 3

The melting and boiling points

Question 4

Use of melting and boiling points:

Answer 4

-to identify pure substances

Question 5

Test for purity of water:

Answer 5

-is that its melting point is 0 degrees and its boiling point is exactly 100 degrees

Question 6

Melting and boiling points of an impure substance:

Answer 6

Impurities tend to lower the melting points of a substance and raise the boiling points

Question 7

Melting point of purified sample of caffeine:

Answer 7

234-237 degrees

Question 8

Melting point of impure sample of caffeine:

Answer 8

180-220 degrees

Question 9

What is a formulation?

Answer 9

A mixture that has been made of definite proportions, designed to give a product the best properties to carry out a function

Question 10

Examples of formulations:

Answer 10

Fuels, alloys, fertilisers, cosmetics, food products

Question 11

Formulations in tablet form:

Answer 11

Aid their dissolving at the most effective place in the digestive tract

Question 12

What do paints contain:

Answer 12

-pigment, to provide colour
-a binder, to help paint attach
-a solvent, help pigment spread

Question 13

What do washing up liquids contain?

Answer 13

-a surfactant, to remove the grease

-water, to thin out the mixture so it squirts easily

-colouring and fragrance addictives

-rinse agent, to help water drain off

Question 14

What might chromotography be used for?

Answer 14

To seperate and identify mixtures of amino acids

Question 15

Amino acids

Answer 15

They are colourless but appear as purple spots on paper when sprayed with a locating agent and dried

Question 16

Rquired practical for paper chromotography?

Answer 16

Seperate dyes in inks or food colourings

Question 17

What does chromotography always involve?

Answer 17

Mobile phase and stationary phase

Question 18

Process of chromotography:

Answer 18

-The mobile phase moves through the stationary phase
-each component in the mixture will have a different attraction for the mobile phase and stationary phase
-substance with stronger attraction to mobile phase will travel a greater distance in a given time
-substance with stronger attraction to stationary phase will travel less

Question 19

What is the mobile phase in paper chromotography?

Answer 19

The solvent

Question 20

What is the stationary phase in paper chromotography?

Answer 20

The paper

Question 21

What will the results be if the unknown sample is a mixture of compounds?

Answer 21

There will be more than one spot formed

Question 22

What does a single spot suggest?

Answer 22

Its a pure substance

Question 23

Rf (retention factor) equation

Answer 23

Distance moved by substance/distance moved by solvent

Question 24

Rf values:

Answer 24

Can be measured and matched against databases to identify substances

Question 25

Test for hydrogen

Answer 25

A lighted splint pops

Question 26

Example of equation to make hydrogen gas to test:

Answer 26

Zince + sulfuric acid ➡️ zince sulfate + hydrogen

Question 27

Test for oxygen

Answer 27

A glowing splint relights

Question 28

How to test for oxygen?

Answer 28

-collect 15cm^3 hydrogen peroxide solution in a conical flask
-add manganese oxide from the end of spatula
-inset glowing splint in the mouth of flask

Question 29

Test for carbon dioxide?

Answer 29

Limewater turns milky (cloudy white)

Question 30

How to test for carbon dioxide?

Answer 30

Bubble carbon dioxide gas through limewater using approapriate apparatus

Question 31

Test for chlorine?

Answer 31

Damp blue litmas paper turns white (as it gets bleached)