Chemical Analysis C8

Question 1

What is a pure substance in chemistry?

Answer 1

something that only contains one compound or element throughout

Question 2

How can you test for a pure substance?

Answer 2

By checking the boiling and melting point as pure substances have pre determined boiling and melting points

Question 3

What is a formulation?

Answer 3

Formulations are useful mixtures with a precise purpose made by following a specific formula

Question 4

What industry are formulations very prominent in?

Answer 4

The pharmaceutical industry so the drug has the right concentration and correct shelf life

Question 5

Where can you find formulations in everyday life?

Answer 5

Cleaning products, fuel, cosmetics, fertilisers

Question 6

What is chromatography?

Answer 6

An analytical method used to separate the substances in a mixture. It can then be used to identify substances

Question 7

What is a mobile phase?

Answer 7

Where the molecules can move. This is always a liquid or gas

Question 8

What is a stationary phase?

Answer 8

Where the molecules cant move. This can be a solid or very thick liquid

Question 9

What is the stationary phase in paper chromatography?

Answer 9

The chromatography paper

Question 10

What is the mobile phase in paper chromatography?

Answer 10

The solvent

Question 11

What is the RF value meant to represent?

Answer 11

The ratio between the distance travelled by the dissolved substance and the distance travelled by the solvent.

Question 12

How do you calculate RF value?

Answer 12

by dividing the distance travelled by the dissolved substance and the distance travelled by the substance

Question 13

What is the test for chlorine?

Answer 13

Chlorine bleaches damp litmus paper, turning it white

Question 14

What is the test for Oxygen

Answer 14

when you put a glowing splint inside a test tube containing oxygen, the glowing splint will reignite

Question 14

What is the test for carbon dioxide

Answer 14

Bubbling carbon dioxide through lime water causes the solution to turn cloudy

Question 15

What is the test for hydrogen?

Answer 15

If you hold a lit splint at the end of test tube containing carbon dioxide, you will get a squeaky pop

Question 16

How do you test for sulfates with HCL and Barium chloride?

Answer 16

Use a pipette to add drops of dilute HCL followed by drops of BaCl₂ to test tube. If sulfate ions present a white precipitate will form

Question 17

How to test for halide ions?

Answer 17

add a couple of drops of dilute nitric acid followed by drops of silver nitrate solution.
Chloride: white precipitate (milk)
Bromide: cream precipitate (cream)
iodide: yellow precipitate (butter)

Question 18

What colours form for certain metal ions in flame test?

Answer 18

Lithium ions - Crimson flame
Sodium ions - Yellow flame
Potassium ions - Lilac flame
Calcium ions - Orange red flame
Copper ions - Green flame

Question 19

How does flame emission spectroscopy work?

Answer 19

1: When sample is placed in flame, electrons and become excited and heat up
2: When electrons drop back to normal energy level, light is produced from transferred energy
3: this energy is picked up by spectroscope which shows the different wavelengths of certain lights
4: You can then match the wavelengths to a substance

Question 20

How to test for Carbonates?

Answer 20

By putting a dilute acid in carbonates, carbon dioxide is produced which can be bubbled through limewater which proves that it is carbon dioxide if it turns cloudy

Question 21

How can we test for the presence of metals in a compound other than in a flame test

Answer 21

By adding Sodium hydroxide to a compound it may form a metal hydroxide, many metal hydroxides are insoluble so it will form a precipitate and you can work out what metal it is by the colour

Question 22

What colours will metals form when added to Sodium Hydroxide

Answer 22

Calcium - White
Copper - Blue
Iron 2 - Green
Iron 3 - Brown
Aluminum - White at first but then colourless when in excess Sodium Hydroxide
Magnesium - White