1.9 Chemical Analysis

Question 1

What is a pure substance ?

Answer 1

A pure substance is a single element or compound not mixed with any other substance

Question 2

What is a mixture ?

Answer 2

A mixture is two or more substances mixed together, which are usually easy to separate

Question 3

What is the melting point

Answer 3

The melting point is the temperature at which a solid changes into a liquid

Question 4

What is the boiling point of a substance ?

Answer 4

The boiling point of a substance is the temperature at which a liquid changes into a gas

Question 5

When a substance is pure what is specific to that substance ?

Answer 5

The melting and boiling point of pure substances are specific to that substance and when pure, a substance will have a sharp melting or boiling poin meaning that it does not melt or boil over a range of temperatures

Question 6

How can any impurities in a substance be detected from melting and boiling point analysis ?

Answer 6

• an impure substance will melt over a range of temperatures and at a lower temperature than the expected melting point
• an impure substance will boil over a range of temperatures and at a higher temperature than the expected boiling point

Question 7

How do you determine if a substance is impure by analysing the melting point ?

Answer 7

An impure substance will melt over a range of temperatures and at a lower melting temperature than expected

Question 8

How do you determine if a substance is impure by analysing the boiling point ?

Answer 8

An impure substance will boil over a range of temperatures and at a higher temperature than the expected boiling point

Question 9

What is a formulation ?

Answer 9

A formulation is a mixture that has been designed as a useful product and is formed by mixing together several different substances in carefully measured quantities to ensure the product has the required properties e.g. alloys, fertilisers and medicines

Question 10

What are examples of formulations ?

Answer 10

Alloys
Fertilisers
Medicines

Question 11

What is a solute ?

Answer 11

A solute is the soluble substance which dissolves

Question 12

What is a soluble substance ?

Answer 12

A substance is described soluble if it dissolves in water

Question 13

What is an insoluble substance ?

Answer 13

A substance is described insoluble if it does not dissolve in water

Question 14

What is the solvent ?

Answer 14

The solvent is the liquid in which the solute dissolves in

Question 15

What is a solution ?

Answer 15

The mixture of the solute dissolved in the solvent is a solution

Question 16

What are miscible liquids ?

Answer 16

Miscible liquids mix

Question 17

What is the filtrate ?

Answer 17

The filtrate is the filtered solution

Question 18

What is the residue ?

Answer 18

The residue is the solid which remains on the filter paper (during filtration)

Question 19

What is the distillate ?

Answer 19

The distillate is the solution obtained from distillation

Question 20

What does filtration allow the separation of ?

Answer 20

Filtration allows an insoluble substance to be separated from a soluble substance

Question 21

During filtration what remains on the filter paper ?

Answer 21

The insoluble substance remains on the filter paper and is known as the residue

Question 22

In filtration what is the filtered liquid/solution called ?

Answer 22

The filtered liquid/solution is called the filtrate

Question 23

What apparatus is needed to carry out filtration ?

Answer 23

• A filter funnel
• Filter paper
• A conical flask

Question 24

What is crystallisation ?

Answer 24

Crystallisation is the process of forming crystals from a solution and is carried out by heating a solution in an evaporating basin which is then allowed to cool. Crystals form on cooling.

Question 25

How is crystallisation carried out ?

Answer 25

Crystallisation is carried out by heating a solution in an evaporating basin which is then allowed to cool and Crystals form on cooling.

Question 26

What apparatus is need to carry out crystallisation ?

Answer 26

- An evaporating basin - Gauze - Tripod - Heatproof mat - Bunsen burner - solution

Question 27

How are flame tests carried out ?

Answer 27

- Flame tests are carried out on a solid - A piece of nichrome wire is dipped in concentrated hydrochloric acid and the wire is then dipped into the solid sample - The wire is held in a blue Bunsen burner flame and the colour is observed - The colour of the flame can indicate the presence of specific cations (positive ions)

Question 28

State the ion present in a solid compound if the flame test colour was crimson ?

Answer 28

Li+

Question 29

State the ion present in a solid compound if the flame test colour was yellow/orange ?

Answer 29

Na+

Question 30

State the ion present in a solid compound if the flame test colour was lilac ?

Answer 30

K+

Question 31

State the ion present in a solid compound if the flame test colour was brick red ?

Answer 31

Ca+ Calcium ion

Question 32

State the ion present in a solid compound if the flame test colour was blue-green ?

Answer 32

Cu²+ Copper ion

Question 33

When the flame test is carried out what colour indicates that a Lithium (Li+) ion is present in a solid compound ?

Answer 33

Crimson

Question 34

When the flame test is carried out what colour indicates that a Sodium (Na+) ion is present in a solid compound ?

Answer 34

Yellow/orange

Question 35

When the flame test is carried out what colour indicates that a Potassium (K+) ion is present in a solid compound ?

Answer 35

Lilac

Question 36

When the flame test is carried out what colour indicates that a Calcium (Ca2+) ion is present in a solid compound ?

Answer 36

Brick red

Question 37

When the flame test is carried out what colour indicates that a Copper (Cu2+) ion is present in a solid compound ?

Answer 37

Blue-green