Further Analysis

Question 1

Pure substance

Answer 1

A single element or compound not mixed with any substance

Question 2

Formulation

Answer 2

A mixture of substances designed to be a useful product

Question 3

Impure substance

Answer 3

A substance that contains other substances (impurities)

Question 4

How to identify pure vs impure substance

Answer 4

A pure substance has a fixed melting and boiling point. An impure substance has a range of temperatures.

Question 5

Hydrogen gas test

Answer 5

Lit splint in test tube → gas burns with squeaky pop

Question 6

CO2 test

Answer 6

Bubble gas through limewater → White prep

Question 7

Cl test

Answer 7

Damp blue litmus paper → Bleaches

Question 8

Alkene

Answer 8

Bromine water → Orange to colourless

Question 9

Acid/Alkali

Answer 9

Indicators colour change

Question 10

pH

Answer 10

Universal indicator → colour change

Question 11

Acid

Answer 11

Add metal carbonate

Bubble gas through limewater

If CO2 produced goes cloudy

Question 12

Excited electrons

Answer 12

• When provided with energy, electrons are promoted to higher energy levels in the atom, e.g. thermal energy
• They then drop down to ground state, releasing energy.

Question 13

Why do excited electrons produce light

Answer 13

• Different atoms have different electron arrangements, giving off different light frequencies.
• Some frequencies are in the visible region of the EM spectrum.

Question 14

Li+ (flame)

Answer 14

Crimson

Question 15

Na+ (flame)

Answer 15

Yellow

Question 16

K+ (flame)

Answer 16

Lilac

Question 17

Ca 2+ (flame)

Answer 17

Orange/Red

Question 18

Cu 2+ (flame)

Answer 18

Green

Question 19

Limitations of flame tests for identifying ions

Answer 19

• Some colours of flame are hard to tell from their background
• Some metals give similar colours of flame
• Some metals give no flame colour as the frequency they give off is not in visible light e.g. UV rays or Infrared

A mixture of metals will give a mixture of colours. One colour may mask the others.

Question 20

Al 3+ NaOH

Answer 20

White

Question 21

Ca 2+ NaOH

Answer 21

White

Question 22

Mg 2+ NaOH

Answer 22

White

Question 23

Cu 2+ NaOH

Answer 23

Blue

Question 24

Fe 2+ NaOH

Answer 24

Green

Question 25

Fe 3+ NaOH

Answer 25

Brown

Question 26

Stationary phase

Answer 26

Paper

Question 27

Mobile phase

Answer 27

Water

Question 28

Separates chemicals based on the

Answer 28

Solubility of components. The more soluble it is, the more it moves across the chromatogram in a given time.

Question 29

Rf values from chromatographs

Answer 29

Distance chemical moves / Distance solvent moves

Question 30

Rf values to draw conclusions about substances

Answer 30

- Pure substances will show one result per chemical. - Mixtures will show more than one. - Identical chemicals will move at the same rate. → The retention factor (proportion of the chromatograph they cover) will be the same.

Question 31

Carbonate ions

Answer 31

Add a dilute acid → Effervescence MUST BE DONE FIRST. CARBONATES GIVE FALSE POSITIVE RESULTS.

Question 32

Sulfate ions

Answer 32

Add HCl to check for no CO Add BaCl → White precipitate

Question 33

Halide ions

Answer 33

Add HNO3 to check for no CO Silver nitrate (dissolves in dilute NH4OH)

Question 34

Cl- Br- I-

Answer 34

White Cream Yellow

Question 35

Flame emission spectroscopy description

Answer 35

Mechanical methods to scan individual frequencies of light

Question 36

Advantages of flame spectrometry

Answer 36

Even tiny quantities of metal can be identified Mixtures can be analysed and compared to known spectra to identify the contents

Question 37

Uses

Answer 37

Detection of trace elements Determining the composition of stars

Question 38

Qualitative chemical tests

Answer 38

Simple Inaccurate Requires larger samples

Question 39

Instrumental tests

Answer 39

Rapid Sensitive Accurate Expensive

Question 40

- Describe why qualitative may be used over instrumental

Answer 40

Simpler and less expensive

Question 42

Mass spectrometer

Answer 42

Reports relative mass of compounds

Answer 43

Separates mixture by compounds so that they can be identified and gives their concentration