C6 CHEMICAL ANALYSIS

Question 1

pure substance?

Answer 1

consists only of one element or one compound

Question 2

how do you determine if a substance is pure?

Answer 2

measure its boiling and melting point

Question 3

when does a pure substance melt?

Answer 3

at a specific fixed temperature

Question 4

when does a pure substance boil?

Answer 4

at a specific fixed boiling point

Question 5

when does an impure substance melt or boil?

Answer 5

over a range of temperatures

Question 6

what is a formulation?

Answer 6

complex mixture that has been designed as a useful product.

in a formulation , the quantity of each component is carefully measured so that the product has the properties we need.

Question 7

examples of formulation?

Answer 7

fuels , cleaning products , paints , medicines, alloys , fertilisers and food

Question 8

what does paper chromatography allow us to do?

Answer 8

separate substances based on their different solubilitys

Question 9

what does paper chromatography allow us to do?

Answer 9

separate substances based on their different solubilitys

Question 10

explain paper chromatography

Answer 10

draw a pencil line near the bottom on the chromatography paper.

we put a dot of our first colour onto the pencil line next to that we put our second colour onto the pencil line (we can use many colours as long as we have space on the pencil line)

place the bottom into the solvent (liquid which dissolves substances)

solvent moves up the paper, it dissolves the ink and the two coloured dots , these are carried up the paper as well

Question 11

stationary phase in paper chromatography?

Answer 11

the paper does not move

Question 12

stationary phase in paper chromatography?

Answer 12

the paper does not move

Question 13

mobile phase in paper chromatography?

Answer 13

the solvent does move

Question 14

mobile phase in paper chromatography?

Answer 14

the solvent does move

Question 15

how do you know if we have a pure compound on the paper?

Answer 15

it will produce a single spots in all solvents

Question 16

how do you know if we have a pure compound on the paper?

Answer 16

it will produce a single spots in all solvents

Question 17

how do you know if we have a mixture on the paper?

Answer 17

may separate into different spots depending on the solvent

Question 18

how do you know if we have a mixture on the paper?

Answer 18

may separate into different spots depending on the solvent

Question 19

how do you know if we have a mixture on the paper?

Answer 19

may separate into different spots depending on the solvent

Question 20

how do you know if we have a mixture on the paper?

Answer 20

may separate into different spots depending on the solvent

Question 21

why does paper chromatography work?

Answer 21

because different substances have got different solubilities

more soluble substance travels further up the paper then a substance which is less soluble

Question 22

why does paper chromatography work?

Answer 22

because different substances have got different solubilities

more soluble substance travels further up the paper then a substance which is less soluble

Question 23

why do we draw our starting line in pencil in chromatography?

Answer 23

if we drew the line in pen , the pen ink would move up the paper with the solvent

Question 24

why do we draw our starting line in pencil in chromatography?

Answer 24

if we drew the line in pen , the pen ink would move up the paper with the solvent

Question 25

problems with chromatography?

Answer 25

several different substances could have the same Rf value. We might need to repeat this experiment using a different solvent

if this substance has never been analysed before, then there will not be an Rf value on the database

Question 26

test for hydrogen?

Answer 26

remove the bung and insert a burning splint, hydrogen gas burns rapidly and produces a pop sound

Question 27

test for oxygen?

Answer 27

insert a glowing splint into the test tube of oxygen, the splint relights (bursts into flames)

Question 28

test for carbon dioxide?

Answer 28

use lime water ( aqueous solution of calcium hydroxide.
draw some of the gas into a plastic pipette.
bubble the gas through the lime water, if we repeat this, the lime water may turn cloudy = carbon dioxide

Question 29

test for chlorine?

Answer 29

insert damp litmus paper into the mouth of the test tube, chlorine bleaches litmus paper white