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Flashcards in GCSE Key Topics Revision Deck (60):
1

What is HPLC or Gas-Liquid Chromatography used for?

To separate mixtures of volatile liquids.

2

What are the advantages of Mass Spectrometry/HPLC ?

Small samples are only required

Results are obtained quick

Gas-Liquid Chromatography and Mass Spectrometry can be combined to separate and identify compounds. This allows chemists to determine exactly what compounds are contained in a sample of an unknown mixture.

3

What are the disadvantages of Mass Spectrometry/HPLC ?

Equipment expensive

Requires the expertise of trained analytical chemists

Care is taken too observe the necessary health and safety procedures

4

Test for Cations

Flame Test - Method

Clean a nichrome wire (a nickel-chromium alloy) by dipping it into concentrated hydrochloric acid.

Hold the wire in a hot Bunsen flame. Repeat until the wire does not produce any colour in the flame.

Dip the clean nichrome wire into the concentrated hydrochloric acid again and dip it into a small amount of the unknown solid.
(A small sample of he solid will stick to the wire)

Place the wire in the Bunsen flame

Observe the colour of the flame

5

Results for the: Test for Cations - Flame Test

Sodium ion - Yellow (persistent)

Potassium ion - Lilac

Calcium ion - Brick red

Barium ion - Apple green

Copper ion - Green/Blue

6

Test for Cations

Using Sodium Hydroxide Solution - Method

Dissolve a small sample of the solid salt in water

Place approximately 10cm*3 of the solution into a test tube

Add Sodium hydroxide solution drop by drop

Observe the colour of the precipitate if one is produced

For any white precipitate produced, continue to add Sodium hydroxide solution, drop by drop

Observe what happens to the precipitate.

7

Test for Cations

Using Sodium hydroxide solution - Results

Blue - Copper(II) ion

Green - Iron(II) ion

Red-Brown - Iron(III) ion

White - Magnesium ion

White precipitate that redissolves in excess Sodium hydroxide solution - Aluminium ion or Zinc ion

8

Test for Anions

Test for Halide ions - Method

Dissolve a small sample of the solid salt in water

Place approximately 10cm*3 of the solution into a test tube

Add four drops of nitric acid

Add silver nitrate solution drop by drop

Observe the colour of the precipitate if one is produced

9

Test for anions

Test for Halide ions - Results

Colour of precipitate produced

White - Chloride ion

Cream - Bromide ion

Yellow - Iodide ion

10

Test for anions

Test for Sulfate ions - Method

Dissolve a small sample of the solid salt in water

Place about 10cm*3 of the solution into a test tube

Add barium chloride solution drop by drop

Observe the colour of the precipitate if one is produced

11

Test for anions

Test for Sulfate ions - Results

Colour of the precipitate

White - Sulfate ions are present

12

Test for anions

Test for Carbonate ions - Method

Add hydrochloric acid to the solid salt

Collect and test any gas formed with limewater

If the limewater turns milky/cloudy the gas evolved is carbon dioxide and the salt is a carbonate

13

Factors affecting solubility

Volume of solvent

Temperature of solvent

Stirring the solution (Kinetic Energy)

Increasing the surface area of the solute

14

Definition - Hydrated

When some solids crystallise from aqueous solution they contain water and are said to be hydrated.

15

Anhydrous - Definition

When some solids lose their crystal structure and water of crystallisation, they are said to be anhydrous.

16

Dehydration - Definition

The removal of the elements of water from a compound to form a new compound.

17

Water of crystallisation

Water that is chemically combined with the solid and forms part of the compound. Water chemically joined in this way is called water of crystallisation.

18

How can water of crystallisation be removed from the compound?

Heating the hydrated solid to constant mass.

19

Safety precautions when carrying out experiments with halogen gases.

Safety gloves

Fume cupboard

Safety glasses

20

What colour will bromine dissolved in water appear in low, medium and high concentrations?

Low = Yellow

Medium = Orange

High = Brown

21

What colour will iodine dissolved in water appear in low, medium and high concentrations?

Low = Yellow

Medium = Brown

High = Purple?

(Think of iodine solution in biology which will turn blue/black in the presence of starch)

22

What is Chromatography used for?

To separate mixtures of coloured compounds

23

Similarities and differences between simple distillation and fractional distillation.

Fractional Distillation

- Used to separate liquids with close boiling points

- Uses a complex apparatus with a fractionating column

- Process has to be repeated several times to get the pure components

- Cannot be used to separate a solvent from a solute

- Used in crude oil refinery

Simple Distillation

- Simple distillation is used to separate liquids with boiling point gaps of at least 50 degrees (apart from water and ethanol = 22°C boiling point gap)

- Uses a simple apparatus with 2 flasks and a condenser (Liebeg condenser)

- Process doesn't have to be repeated to get the pure components

Can be used to separate a solvent from a solute

24

Element definition

A substance that consist of only one type of atom

25

Compound definition

A substance that consists of two or more different elements chemically bonded together

26

Mixture definition

A mixture consisting of two or more substances not chemically bonded together.

They can be easily separated by, for example iron and sulfur, salt and sand.

27

Distillation definition

A process that can be used to separate a pure liquid from a mixture of liquids.

28

In Mass Spectrometry, all of the atoms and molecules are measured relative to ________________________.

Answer: one twelfth the mass of a Carbon-12 atom,

12
6 C

29

By carefully interpreting the data from mass spectrometry we can see that it is possible to deduce ____________________________.

Answer:

- The relative atomic masses of elements

- The number of isotopes an element contains

- The relative molecular masses of compounds and molecules

30

Molecule definition

Two or more atoms covalently bonded

31

Copper(II) Oxide is the colour .....

Black

32

Copper(II) Carbonate is ....

Green

33

Hydrated Copper(II) Sulfate is ....

Blue

34

Most Copper Salts are ____ in solution.

Blue

35

Group 1 Compounds

Group 2 Compounds

Aluminium Compounds
Zinc Compounds

Colour = ?

Solution Colour = ?

Colour = White

Solution = Colourless

36

Why is it that some alloys are harder than the pure metal they contain?

Alloys contain atoms of different sizes which distorts the regular arrangement of atoms. This makes it more difficult for the layers to slide easily over each other.

37

Uses of Aluminium

Overhead electrical wiring

Alloys for aircraft

38

Uses of Copper

Electrical wiring

Plumbing

Brass (Alloy)

Coinage

39

Uses of Iron

Bridges

Infrastructure

40

Uses of Magnesium

Flares

High strength alloys for aircraft

41

Chemical reactions use up _________ and produce new substances called ________.

Answers:

Reactants

Products

42

John Newland proposed the Law of Octaves but his work was rejected by other scientists. Why?

- His classification assumed that all of the elements had been discovered, even though a number of new elements had been recognised a few years prior to his publication

He grouped some elements together which were not alike, e.g Manganese + Nitrogen, Phosphorus + Arsenic, Copper + [Lithium + Sodium + Potassium + Rubidium]

He placed two elements together, Cobalt and Nickel

43

Dmitri Mendeleev created the 'Periodic Table' in 1869. What features did his arrangement and classification of elements include?

He arranged elements in order of increasing relative atomic mass.

He placed elements with similar properties in the same vertical columns (Groups).

He left gaps - For undiscovered elements, helped keep his elements in their proper groups and allowed him to predict elements with unexpected accuracy (e.g Gallium and Germanium).

44

Mendeleev's Periodic Table of 1869 differs from today's Modern Periodic Table of elements. In what ways?

Mendeleev = Increasing atomic mass
Today = Atomic number

Group 8/0 Noble Gases added

Transition metals added in between group 2 and 3

Some groups have been given common names

Clear distinction between metals and non-metals thanks to a solid black line starting at group 3 separating the elements

45

Fluorine

Colour and state at 25°C

Yellow

Gas

46

Chlorine

Colour and State at 25°C

Green

Gas

47

Bromine

Colour and state at 25°C

Brown

Liquid

48

Iodine

Colour and state at 25°C

Purple/Dark grey

Solid

49

Astatine

Colour and state at 25°C

Black

Solid

50

The darkness in colour and appearance of the group 7 elements _________ as you go down the group.

Increases

51

The melting and boiling points of the Group 7 halogen elements _________ as you move down the group.

Increases

Fluorine has the lowest melting and boiling point.

52

Acid + Alkali = ?

Salt + Water

53

What is concentration measured in?

mol/dm3️⃣

54

Give an example of a strong acid

Hydrochloric acid

Sulfuric acid

Nitric acid

55

Give an example of a strong alkali

Sodium hydroxide

Potassium hydroxide

56

Give an example of a weak acid

Ethanoic acid

Carbonic acid

57

Give an example of a weak alkali

Ammonia

58

Pure hydrogen burns with a squeaky pop and can be tested by placing a lighted splint into a test tube containing Hydrogen gas. The combustion of hydrogen gas in the air (With oxygen) produces a pop. Recall the balanced symbol equation.

2H2️⃣ + O2️⃣ --> 2H2️⃣O

59

Give the chemical name for limewater

Calcium hydroxide solution

60

To test for Cations, one may use Sodium hydroxide solution. Magnesium ions, Zinc ions and Aluminium ions all form white precipitates in this test. When excess Sodium hydroxide solution is added, the Magnesium precipitate does not dissolve, leaving only Zinc and Aluminium. What alkali could be used to prove that Zinc ions are present, increasing the validity of the test?

Ammonium hydroxide solution

If Zinc ions are present a white precipitate will form (Zinc hydroxide) which will, unlike Aluminium, will dissolve in excess Ammonium hydroxide solution.