c8 - chemical analysis

Question 1

What is a pure substance

Answer 1

A single element or compound, not mixed with any other substance.

Question 2

What is a formulation

Answer 2

A mixture that has been designed as a useful product.

Question 2

How could you distinguish between a pure substance and a mixture

Answer 2

Pure substances melt and boil at specific temperatures. Melting and boiling point data could be used.

Question 3

How are formulations made

Answer 3

Mixing the components in carefully measured quantities to ensure the product has the required properties.

Question 4

Give two examples of formulations.

Answer 4

Fuels, cleaning agents, paints, medicines, alloys, fertilisers and foods.

Question 5

what is chromatography

Answer 5

to help separate mixtures and determine what substances are in each mixture

Question 6

what is the stationary phase

Answer 6

the paper

Question 7

what is the mobile phase

Answer 7

the mixture

Question 8

what is the equation to find the rf value

Answer 8

distance moved by substance / distance moved by solvent

Question 9

how to test for hydrogen

Answer 9

uses a burning splint held
at the open end of a test tube of the gas.
Hydrogen burns rapidly with a pop sound.

Question 10

how to test for oxygen

Answer 10

uses a glowing splint inserted into a test tube of the gas. The splint relights in oxygen.

Question 11

how to test for carbon dioxide

Answer 11

uses an aqueous solution of calcium hydroxide (lime water). When carbon dioxide is shaken or bubbled through limewater the limewater turns milky

Question 12

how to test for chlorine

Answer 12

uses litmus paper. When damp litmus paper is put into chlorine gas the litmus paper is bleached and turns white.

Question 13

What is a flame test

Answer 13

Rod dipped in water and then in the compound; placed in flame; observe colour of flame.

Question 14

What colour flame would the following metal ions have in a flame test

Lithium
Sodium
Potassium
Calcium
Copper

Answer 14

Lithium crimson red
Sodium yellow
Potassium lilac
Calcium orange-red
Copper green

Question 15

What might cause some flame colours to be masked

Answer 15

A sample containing a mixture of ions.

Question 16

What is a precipitate

Answer 16

A insoluble solid product produced in a liquid.

Question 17

Sodium hydroxide is used to identify some metal ions. What colour precipitate do aluminium, calcium and magnesium ions
form

Answer 17

White.

Question 18

How is are aluminium ions distinguished from calcium and magnesium ions in the reaction with sodium hydroxide

Answer 18

Aluminium hydroxide precipitate dissolves in excess sodium hydroxide solution.

Question 19

What colour precipitate do the following ions make with sodium hydroxide

Copper (II)
Iron (II)
Iron (III)

Answer 19

Copper (II) blue
Iron (II) green
Iron (III) brown

Question 20

How would you test for a carbonate

Answer 20

React with dilute hydrochloric acid to form carbon dioxide gas.

Question 21

How would you test for halide ions

Answer 21

Produce precipitate with silver nitrate in the presence of nitric acid.

Question 22

How could you distinguish between halide
ions?

Silver chloride
silver bromide
silver iodide

Answer 22

Silver chloride = white
silver bromide = cream
silver iodide = yellow.

Question 23

How would you test for sulfate ions

Answer 23

Add barium chloride solution in the presence of hydrochloric acid; white precipitate formed.

Question 24

Give three advantages of instrumental methods for detecting ions compared with chemical methods.

Answer 24

accurate
sensitive
rapid

Question 25

What is flame emission spectroscopy used for

Answer 25

To analyse metal ions in solution.

Question 26

How is flame emission spectroscopy carried out

Answer 26

Sample is put into a flame, light given out is passed through a spectroscope, line spectrum produced is analysed to identify
metal ions