Topic C4 - Chemical Change

Question 1

What does the lower PH numbers mean

Answer 1

That they are more acidic

Question 2

What does the higher pH numbers mean

Answer 2

That they are more alkaline

Question 3

How can you measure the pH of the solution

Answer 3

By using an indicator in the form of a dye that changes colour. For example universal indicator

Are using a pH probe attached to a pH meter

Question 4

What is an acid

Answer 4

an acid is a substance that forms aqueous solution with a pH of less than seven. Acids form H+ ions in water

Question 5

What is a base

Answer 5

Is a substance with a pH greater than seven

Question 6

What is an alkali

Answer 6

Is a base that is dissolved in water to form a solution with a pH greater than seven. Alkalis form OH- ions in water

Question 7

What is the Chemical formula of hydrochloric acid

Answer 7

HCl

Question 8

What is the symbol equation for nitric acid

Answer 8

HNO3

Question 9

What is the chemical formula for sulfuric acid

Answer 9

H2SO4

Question 10

What is the chemical formula for phosphorus acid

Answer 10

H3PO4

Question 11

What are common bases

Answer 11

Metal oxides

Metal carbonates

Question 12

What are common alkalis

Answer 12

Ammonia

Metal hydroxide

Question 13

What is the Chemical formula of ammonia

Answer 13

NH3

Question 14

What is the salt created by sulphuric acid

Answer 14

Sulfates

Question 15

What is the salt created by hydrochloric acid

Answer 15

Chloride

Question 16

What is the salt created by nitric acid

Answer 16

Nitrate

Question 17

What is the salt created by phosphoric acid

Answer 17

Phosphate

Question 18

What are the products created by a

acid + reactive metal

Reaction

Answer 18

salt + hydrogen

Question 19

What are the products created by a

acid + base/alkali

Reaction

Answer 19

salt + water

Question 20

What are the products created by a

acid + carbonate

Reaction

Answer 20

salt + water + carbon dioxide

Question 21

How do we know if an acid is strong

Answer 21

If the ions completely ionise in water

All acid particles dissociate to release H+ ions

Question 22

How do we know if an acid is weak

Answer 22

If the ions does not fully ionise in solution

Only a small proportion of acid particles dissociate to release H+ ions

This is a reversible reaction

Question 23

What is PH a measure of

Answer 23

The concentration of H+ ions in the solution

Question 24

How do you workout concentration in terms of ph

Answer 24

For every decrease of one on the pH scale, the concentration of H+ ions increased by a factor of 10

Question 25

What is the reactivity series

Answer 25

Is a list of metals in order of reactivity towards other substances

Question 26

How are metal ores formed

Answer 26

By oxidation

Question 27

How are metals extracted from its ores

Answer 27

By reduction

Question 28

What is oxidation

Answer 28

The gain of oxygen

Question 29

What is reduction

Answer 29

The loss of oxygen

Question 30

How do you determine if a metal can be extracted by reduction with carbon

Answer 30

It is determined by the position of the metal in the reactivity series against carbon

Question 31

What happens if the metal is higher than carbon in the reactivity series

Answer 31

It will have to be extracted using electrolysis which is explosive

Question 32

How do you remember redox reactions

Answer 32

OIL RIG ``` Oxidisation is loss reduction is gain ``` In terms of electrons

Question 33

What's the meaning of electrolysis

Answer 33

Splitting up with electricity

Question 34

What happens in electrolysis

Answer 34

1) During electrolysis and electric current is passed through an electrolyte. The ions move towards the electrodes 2) The positive ion (cation) in the electrolyte will move towards the cathode (the negative electrode) and gain electrons 3) The negative ion (anion) in the electrolyte will move towards the anode (the positive electrode) and lose electrons

Question 35

What happened to cations in electrolysis

Answer 35

They are reduced (redox) to the element at the cathode

Question 36

What happens to nonmetals in electrolysis

Answer 36

They are oxidised (redox) to the element at the anode

Question 37

What happens in electrolysis of aqueous solutions

Answer 37

1) in aqueous solutions: there are ions from the ionic compound as well as hydrogen ions and hydroxide ions from water 2) at the cathode- if H+ ions and metal ions are present . Hydrogen gas will be produced if the metal ions form an element that is more reactive than hydrogen If it is less reactive than hydrogen a solid layer of the pure metal will be produced instead 3) At the anode - if OH- and halide ions (Cl-,Br- I-) are present: Molecules of chlorine,bromine and iodine and will form If no halide ions (Cl-,Br- I-) are present: Then the OH- ions are discharged and oxygen will be formed