Chemical Analysis

Question 1

What is a pure substance?

Answer 1

A substance containing a single element or compound (that is not mixed with another substance)

Question 2

What is an impure substance?

Answer 2

A substance containing more than one type of element or compound in a mixture.

Question 3

How do you calculate the Rf value?

Answer 3

Distance moved by substance / distanced moved by solvent

Question 4

What numbers will the Rf value always be between?

Answer 4

0 and 1

Question 5

In chromatography, what is shown by how far the substance moves up the paper?

Answer 5

Higher up = more soluble

Question 6

In chromatography, what does it mean if a substance produces only one spot?

Answer 6

It is pure

Question 7

In chromatography, why must the line be drawn in pencil?

Answer 7

Pen would dissolve and travel up the paper

Question 8

What is the test for hydrogen?

Answer 8

Hold a lit splint near gas.
Positive = squeaky pop sound

Question 9

What is the test for oxygen?

Answer 9

Hold glowing splint near gas.
Positive = splint relights

Question 10

What is the test for carbon dioxide?

Answer 10

Bubble gas through limewater.
Positive = limewater turns cloudy

Question 11

What is the test for chlorine?

Answer 11

Hold piece of damp litmus paper near gas.
Positive = litmus paper bleached white

Question 12

How do you test for aluminium ions?

Answer 12

Slow addition of excess sodium hydroxide solution
Positive = white precipitate that eventually dissolves.

Question 13

How do you test for calcium ions?

Answer 13

Addition of excess sodium hydroxide solution
Positive = white precipitate that does not dissolve.

Question 14

How do you test for magnesium ions?

Answer 14

Addition of excess sodium hydroxide solution
Positive = white precipitate that does not dissolve.

Question 15

How do you test for copper (II) ions?

Answer 15

Add sodium hydroxide solution
Positive = blue precipitate

Question 16

How do you test for iron (II) ions?

Answer 16

Add sodium hydroxide solution
Positive = green precipitate

Question 17

How do you test for iron (III) ions?

Answer 17

Add sodium hydroxide solution
Positive = brown precipitate

Question 18

How do you test for carbonate anions?

Answer 18

Add dilute acid
Positive = CO2 gas formed

Question 19

How do you test for chloride anions?

Answer 19

Add silver nitrate solution in presence of nitric acid
Positive = white precipitate formed

Question 20

How do you test for bromide anions?

Answer 20

Add silver nitrate solution in presence of nitric acid
Positive = cream precipitate formed

Question 21

How do you test for iodide anions?

Answer 21

Add silver nitrate solution in presence of nitric acid
Positive = yellow precipitate formed

Question 22

How do you test for sulfate anions?

Answer 22

Add barium chloride solution in presence of hydrochloric acid
Positive = white precipitate formed

Question 23

Flame tests: what is the positive result for lithium?

Answer 23

Crimson

Question 24

Flame tests: what is the positive result for sodium?

Answer 24

yellow

Question 25

Flame tests: what is the positive result for potassium?

Answer 25

Lilac

Question 26

Flame tests: what is the positive result for calcium?

Answer 26

Orange-red

Question 27

Flame tests: what is the positive result for copper?

Answer 27

Green

Question 28

What is instrumental analysis?

Answer 28

Using complex scientific equipment to identify substances.

Question 29

What are 3 advantages of instrumental analysis?

Answer 29

Quick, accurate, sensitive

Question 30

What information does flame emission spectroscopy produce?

Answer 30

The wavelength of light given off by metal in a flame To identity of the metal and its concentration

Question 31

What group of the Periodic Table are the halogens found in?

Answer 31

Group 7

Question 32

What are ions of Group 7 elements known as?

Answer 32

Halide ions

Question 33

What is added to halide ions when tested for?

Answer 33

Nitric acid, then silver nitrate

Question 34

What precipitate is formed by a chloride ion? (in nitric acid + silver nitrate solution)

Answer 34

White

Question 35

What precipitate is formed by a bromide ion? (in nitric acid + silver nitrate solution)

Answer 35

Cream

Question 36

What precipitate is formed by an iodide ion? (in nitric acid + silver nitrate solution)

Answer 36

Yellow

Question 37

What are flame tests used to test for?

Answer 37

Alkali metals

Question 38

What group on the Periodic Table is the alkali metals?

Answer 38

Group 1

Question 39

What colour does a flame turn when lithium ions are present?

Answer 39

Crimson

Question 40

What colour does a flame turn when sodium ions are present?

Answer 40

Yellow-orange

Question 41

What colour does a flame turn when potassium ions are present?

Answer 41

Lilac

Question 42

What colour does a flame turn when calcium ions are present?

Answer 42

Brick red

Question 43

What colour does a flame turn when barium ions are present?

Answer 43

Apple green

Question 44

What is the mobile phase in chromatography?

Answer 44

The solvent that moves through the paper, carrying different substances with it

Question 45

What is the stationary phase in chromatography?

Answer 45

It is contained on the paper and does not move through it (e.g: chromatography paper)