chemical analysis

Question 1

what is a pure substance

Answer 1

contains only one type of compound or element

Question 2

physical properties of pure substances

Answer 2

• melt and boil at specific temperatures
  
  • helps us identify what substance it is

Question 3

impure substance properties

Answer 3

• melting point decreases
• boiling point increases

Question 4

Formulation definition

Answer 4

mixtures that have been prepared using a specific formula
- precise amount of different
components
- have a particular function

Question 5

chemical analysis

Answer 5

instruments and methods we use to identify, separate and quantify different substances

Question 6

example of paint and why it has to be a formulation

Answer 6

• pigment
• solvent - to dissolve the other components
• binder - to stack onto the wall

Question 7

test for chlorine

Answer 7

take a damp litmus paper into a test tube with the sample gas
- if chlorine is present the damp litmus
paper will turn blue to white

Question 8

Why might the blue litmus paper turn red before turning white when testing for chlorine

Answer 8

The solution of chlorine is acidic

Question 9

risk assessment of chlorine test

Answer 9

wear a mask as chlorine is poisonous

Question 10

Test for oxygen

Answer 10

insert a glowing splint into a test tube with sample gas
- if oxygen is present the splint will
relight

Question 11

Test for hydrogen

Answer 11

when a burning splint is placed near a test tube with hydrogen, there should be a squeaky pop

Question 12

when testing for hydrogen, why is there a squeaky pop noise?

Answer 12

the heat energy from the flame causes the hydrogen to burn with the oxygen in the air to form water

Question 13

When testing for oxygen, why does the splint relight

Answer 13

burning requires oxygen so providing a lot of O2 will spark up the reaction again

Question 14

test for carbon dioxide

Answer 14

bubbling carbon dioxide through limewater causes the soultion to turn cloudy

Question 15

When testing for carbon dioxide, why does calcium hydroxide turn cloudy?

Answer 15

calcium carbonate (product) is a solid and these solid particles makes it appear cloudy

Question 16

what is a chromatogram

Answer 16

the pattern of spots on the filter paper after chromatography

Question 17

mobile phase

Answer 17

where molecules can move
- liquid
- gas

Question 18

stationary phase

Answer 18

where molecules cant move
- solid
- thick liquid

Question 19

Rf value equation

Answer 19

distance travelled by solvent (H2o)

Question 20

What is chromotography used for?

Answer 20

To separate a mixture of soluble substances in liquids

Question 21

What are anions

Answer 21

negatively charged ions

Question 22

carbonate reacting with acid word equation

Answer 22

carbonate + acid —->
salt + carbon dioxide + water

Question 23

what do carbonate substances contain?

Answer 23

. -2
CO
3

Question 24

test for carbonate ions

Answer 24

• use a pipette to add a few drops of
  dilute HCL acid to a test tube
  containing the sample
• then bubble the test tube through lime
  water
• it will turn cloudy

Question 25

sulfate ions

Answer 25

. -2 SO 4

Question 26

test for sulfate

Answer 26

- using a pipette add few drops of dilute HCL acid ( removes any other ions in our sample ) - add few drops of barium chloride solution - positive result = white precipitate

Question 27

what are the halide ions

Answer 27

- chloride - ions - iodide - ions - bromide - ions

Question 28

test for halides

Answer 28

- with pipette add few drops of dilute nitric acid - add silver nitrate so the silver ions can react with the halide to form a precipitate - colour of precipitate depends on the halide the silver ions react with

Question 29

sulfate word equation

Answer 29

. +2 -2 Ba + SO ----> BaSO 4 4

Question 30

chlorine colour precipitate

Answer 30

white

Question 31

bromide colour precipitate

Answer 31

cream

Question 32

iodide colour precipitate

Answer 32

yellow

Question 33

what are cations?

Answer 33

positively charge ions

Question 34

positive result for lithium flame test

Answer 34

crimson flame

Question 35

positive result for sodium flame test

Answer 35

yellow flame

Question 36

positive result for potassium flame test

Answer 36

lilac flames

Question 37

positive result for calcium flame test

Answer 37

orange-red flame

Question 38

positive result for copper flame test

Answer 38

green flame

Question 39

what is a limitation of the flame test

Answer 39

if there are 2 or more different metals in the sample the colours of the flames will mix

Question 40

calcium precipitate

Answer 40

white

Question 41

copper precipitate

Answer 41

blue

Question 42

iron II precipitate

Answer 42

green

Question 43

iron III precipitate

Answer 43

brown

Question 44

aluminium precipitate

Answer 44

colourless

Question 45

magnesium precipitate

Answer 45

white