Chemical Analysis

Question 1

What is chromatography used for?

Answer 1

Separate mixtures (mainly inks and dyes) of coloured and non-coloured substances that are soluble in the same solvent

Question 2

What are the 2 phases of chromatography?

Answer 2

Mobile and stationary

Question 3

What does Rf stand for?

Answer 3

Retention factor

Question 4

What is the equation for work out the Rf value?

Answer 4

Rf = distance moved by substance / distance moved by solvent

Question 5

What is a pure substance?

Answer 5

A substance that is made up of only one type of element or compound

Question 6

What is a mixture?

Answer 6

Two or more substance that aren’t chemically bonded together

Question 7

How can you tell if a substance is pure from a graph?

Answer 7

The boiling point is sharp and at a specific temperature

Question 8

How can you tell if a substance is impure from a graph?

Answer 8

The boiling point is a range

Question 9

What is a formulation?

Answer 9

A mixture that’s been designed to produce a useful producr

Question 10

Examples of formulations

Answer 10

Perfume, medicinal drugs, paint, fuels

Question 11

What happens if a substance has a greater attraction to the mobile phase?

Answer 11

It moves a greater distance

Question 12

What happens if a substance has a greater attraction to the stationary phase?

Answer 12

Won’t travel as far

Question 13

How do you test for hydrogen?

Answer 13

Collect the gas, light a split, put fire in test tube

Question 14

What will happen if hydrogen is present?

Answer 14

A squeaky pop sound is made

Question 15

How do you test for oxygen?

Answer 15

Light a wooden split, blow it out until it’s glowing, put it in the gas

Question 16

What will happen if oxygen present?

Answer 16

The splint will relight

Question 17

How do you test for carbon dioxide?

Answer 17

Bubble the gas through limewater

Question 18

What will happen if carbon dioxide is present?

Answer 18

The limewater will go milky/cloudy

Question 19

How do you test for chlorine?

Answer 19

Put damp litmus paper near gas

Question 20

What will happen if chlorine is present?

Answer 20

The litmus paper will turn white

Question 21

How are positive ions formed?

Answer 21

When an atom loses electrons

Question 22

Examples of positive ions

Answer 22

Potassium and Lithium

Question 23

How do you carry out the flame test?

Answer 23

1. Dip a nichrome wire loop into HCl and sterilise it then dip it in HCl again
2. Dip the loop into the metal compound being tested
3. Hold the loop in a blue flame of a bunsen burner
4. Use the colour of the bunsen burner to identify the metal ion

Question 24

What colour does Lithium turn during the flame test?

Answer 24

Crimson

Question 25

What colour does Sodium turn during the flame test?

Answer 25

Yellow

Question 26

What colour does Potassium turn during the flame test?

Answer 26

Lilac

Question 27

What colour does Calcium turn during the flame test?

Answer 27

Orange/Red

Question 28

What colour does Copper turn during the flame test?

Answer 28

Green

Question 29

What metals form a white precipitate during the sodium hydroxide test?

Answer 29

Aluminium, Magnesium, Calcium

Question 30

What metal form a blue precipitate during the sodium hydroxide test?

Answer 30

Copper

Question 31

What metal form a iron(II) precipitate during the sodium hydroxide test?

Answer 31

Green

Question 32

What metal form a iron(III) precipitate during the sodium hydroxide test?

Answer 32

Brown

Question 33

What happens if you add more sodium hydroxide to the precipitate formed by aluminium ions?

Answer 33

It dissolves

Question 34

What is the test for carbonates?

Answer 34

Adding a dilute acid to the metal being tested

Question 35

How do you know if a carbonate is present?

Answer 35

Carbon dioxide is formed

Question 36

What are halides?

Answer 36

Chlorides, bromides and iodides

Question 37

How do you test for halides?

Answer 37

Add dilute nitric acid and silver nitrate to a the halide and allow a precipitate to form

Question 38

What colour precipitates do different halides form?

Answer 38

Iodide ions - yellow Bromide ions - cream Chloride ions - white

Question 39

How do you test for sulphates?

Answer 39

Add HCl and barium chloride the sulphate ion sample

Question 40

How do you know if a sulphate is present?

Answer 40

A white precipitate is formed

Question 41

What are advantages of instrumental analysis?

Answer 41

Accurate, quick, sensitive, can detect small amounts

Question 42

What are disadvantages of instrumental analysis?

Answer 42

Expensive, special training needed

Question 43

What is flame emission spectroscopy used for?

Answer 43

Analysing samples of metal ions

Question 44

How does flame emission spectroscopy work?

Answer 44

In the spectrometer, wavelengths of light are provided to be analysed. Each type of ion emits and absorbs it’s own characteristic pattern of radiation, this is called the line spectrum and it can be used to identify metal ions