Chemical Analysis

Front 1

What is a pure substance?

Back 1

a pure substance may consist of a single element or compound which contains no other substances

Front 2

melting and boiling point of puresubstances?

Back 2

They are sharp

Front 3

How to identify pure substances from graphe

s?

Back 3

straight line on the graph

Front 4

What is paper chromatography used for ?

Back 4

This technique is used to separate substances that have different solubilities in a given solvent

Front 5

How to carry out the chromatography experiment?

Back 5

A pencil line is drawn on chromatography paper and spots of the sample are placed on it. A pencil is used for this as ink would run into the chromatogram along with the samples The paper is then lowered into the solvent container, making sure that the pencil line sits above the level of the solvent, so the samples don’t wash into the solvent container The solvent travels up the paper by capillary action, taking some of the coloured substances with it Different substances have different solubilities so will travel at different rates, causing the substances to spread apart .Those substances with higher solubility will travel further than the others This will show the different components of the ink/dye If two or more substances are the same, they will produce identical chromatograms. If the substance is a mixture, it will separate on the paper to show all the different components as separate spots An impure substance will show up with more than one spot, a pure substance should only show up with one spot.

Front 6

What is the mobile and stationary phase?

Back 6

The mobile phase is the solvent, The stationary phase in paper chromatography is the actual chromatography paper itself

Front 7

How to calculate the reference value of a chromatogram?

Back 7

Front 8

What do we calculate the Rf value for?

Back 8

Rf values is a viable method of identifying unknown mixtures given reference material

Front 9

How to test for Hydrogen gas?

Back 9

If hydrogen is present in a test tube, a lighted splint held near its mouth ignites with a squeaky pop.

Front 10

What is the test for oxygen?

Back 10

If oxygen is present in a test tube, a glowing splint relights when it is held inside.

Front 11

What's the test For Carbon dioxide?

Back 11

Uses limewater.If the gas is carbon dioxide, the limewater turns cloudy

Front 12

How to test for chlorine gas?

Back 12

The test for chlorine makes use of litmus paperIf chlorine gas is present, damp blue litmus paper will turn red and then be bleached white

Front 13

What is the flame tests used for?

Back 13

The flame test is thus used to identify metal ions by the colour of the flame they produce

Front 14

How to do a general flame test?

Back 14

Dip the nichrome wire into the solid sample and place it in the edge of the blue Bunsen flame

Avoid letting the wire get so hot that it glows red otherwise this can be confused with a flame colour

Front 15

Flame test result for :

Lithium

Sodium

Potassium

Calcium

Copper

Back 15

Flame test result for :

Lithium - Red

Sodium - Yellow

Potassium - Lilac

Calcium - Orange/red

Copper - green

Front 16

How to distinguish between Ca2+ and Mg2+ AND Al3+?

Back 16

Ca2+ and Mg2+ ions can be distinguished from Al3+ as calcium hydroxide and magnesium hydroxide precipitates do not dissolve in excess NaOH but aluminium hydroxide does

Front 17

How to distinguish between Ca2+ and Mg2+?

Back 17

Another test could be used to distinguish between the Ca2+ and Mg2+ ions, for example a flame test

Front 18

How to test for metal Cations?

Back 18

Add sodium hydroxide to them

Front 19

What are the effects of adding sodium hydroxide to Aluminium?

Back 19

White precipitate, dissolves in excess sodium hydroxide to form a colourless solution.

Front 20

What are the effects of adding sodium hydroxide to Magnesium ?

Back 20

White precipitate, insoluble so remains in excess sodium hydroxide

Front 21

What are the effects of adding sodium hydroxide to Calcium ?

Back 21

White precipitate, insoluble so remains in excess sodium hydroxide

Front 22

What are the effects of adding sodium hydroxide to Copper ?

Back 22

light blue percapitate, insoluble in excess

Front 23

What are the effects of adding sodium hydroxide to Iron (2) ?

Back 23

Green percapitale, insoluble in excess

Front 24

What are the effects of adding sodium hydroxide to Iron (3) ?

Back 24

Red- Brown percipitate, insoluble in excess

Front 25

How to test for carbonates?

Back 25

Add a few drops of dilute hydrochloric acid. Bubbles are produced if carbonate ions are present. Confirm that the gas is carbon dioxide - limewater turns milky/cloudy.

Front 26

How to test for Halides?

Back 26

Add dilute nitric acid followed by silver nitrate.

Front 27

How to know which Halide iron is which?

Back 27

Silver Chloride - white

Silver bromide - cream

Silver iodide - yellow

Front 28

How to test for sulphates?

Back 28

dilute hydrochloric acid and then add a few drops of aqueous barium chloride

If a sulphate is present then a white precipitate

Front 29

What instruments can we use to do Chemical analysis?

Back 29

Flame Emission Spectroscopy

Front 30

What are the advantages of using instrumental methods

Back 30

They provide greater accuracyThey are faster and easier to useThey are automated and can perform multiple simultaneous sampling and testingModern instruments are very sensitive and can work with very small sample sizes