2.3 - Acid–base and redox reactions

Question 1

Name and write the formula of some common acids ?

Answer 1

• Hydrochloric acid (HCl )
• Nitric acid ( HNOv3 )
• Sulphuric acid ( Hv2SOv4 )

Question 2

Name and write the formula of some common alkalis ?

Answer 2

• Sodium hydroxide ( NaOH )
• Potassium hydroxide ( KOH )
• Ammonia ( NHv3 )

Question 3

What happens when an acid dissolved in water ?

Answer 3

When an acid dissolves in water it releases H+ ions forming an aqueous solution

Question 4

What happens when an alkali dissolved in water ?

Answer 4

When an alkali dissolved in water it released OH- ions forming an aqueous solution

Question 5

What is the difference between a strong and weak acid ?

Answer 5

• A strong acid is one that dissociates ( ionises ) completely when in water
• A weak acid is one that dissociates partially when in water

Question 6

What is a neutralisation reaction ?

Answer 6

A neutralisation reaction where an acid and alkali react forming a salt and water

Question 7

Write the ionic equation for a neutralisation reaction ?

Answer 7

OH-(aq) + H+(aq) —> Hv2O (l)

Question 8

Write the equation for the following reaction : acid + alkali ?

Answer 8

Acid + alkali —> salt + water

Question 9

Write the equation for the following reaction : Acid + metal carbonate ?

Answer 9

Acid + Metal carbonate —> salt + water + carbon dioxide

Question 10

Describe what you would observe when a metal carbonate reacts with an acid ?

Answer 10

The solid/ metal carbonate would dissolve or disappear and there would be bubbling/ fizzing

Question 11

Write the equation for the following reaction : Acid + Metal oxide ?

Answer 11

Acid + Metal oxide —> salt + water

Question 12

Describe what you would observe when a metal oxide would react with an acid?

Answer 12

The solid/ metal oxide would dissolve or disappear

Question 13

Do you know how to do calculations to find the concentration of an unknown solution ?

Answer 13

Yes

Question 14

Define the term ‘oxidation’ ( both in terms of oxidation number and not ) ?

Answer 14

Oxidation - Oxidation is loss of electrons/ gain of oxygen and when the oxidation number of an element in an atom, molecule or ion increases

Question 15

Define the term ‘reduction’ ( both in terms of oxidation number and not ) ?

Answer 15

Reduction - Reduction is the gain of electrons/ loss of oxygen and when the oxidation number of an element in an atom, molecule or ion decreases

Question 16

What is a monoprotic acid ?

Answer 16

A proton donor that donates one H+ ( one proton )

Question 17

What is a base ?

Answer 17

A proton acceptor, a substance that readily accepts H+ ions

Question 18

What are diprotic and tripotic acids ?

Answer 18

• A diprotic acid is a proton donor which donates two H+ ions ( two protons )
• A triprotic acid is a proton donor which donates three H+ ions ( three protons )

Question 19

Do you know how to use roman numerals to indicate the various oxidation number of elements in a compound ?

Answer 19

Yes

eg. Iron ( II ) chloride
Iron ( III ) chloride

Question 20

What is oxidation number used for ?

Answer 20

Oxidation numbers are assigned to atoms to represent the relative ( in comparison to something else ) state of oxidation of the atom

Question 21

What are the rules for assigning oxidation number ?

Answer 21

1 ) The oxidation number of all elements is ( 0 )
2 ) The oxidation number of ions are the same as their charges
3 ) Overall, oxidation number must equal zero in a compound, and equal the charge of any molecular ion
4 ) Roman numerals give the charge of an ion and oxidation number whether metallic/ non-metallic ( eg. Iron ( ll ) chloride = Fe2+ )

Question 22

How can we determine whether something has been oxidised/ reduced using oxidation number ?

Answer 22

• A substance is oxidised when their oxidation number increases
• A substance is reduced when their oxidation number decreases

Question 23

How do we balance using oxidation number ?

Answer 23

1 ) Assign oxidation numbers and then balance for any species that is oxidised or reduced
2 ) Now balance for electron transfer
3 ) Now finish by balancing other atoms checking charges on each side of the equation are the same

Question 24

Can you use oxidation number to identify what substances have been oxidised/ reduced and whether it is a redox reaction ?

Answer 24

Yes

Question 25

Can you balance an equation using oxidation number ?

Answer 25

Yes

Question 26

What are the anomalies for oxidation number ?

Answer 26

• F always has an oxidation number of ( -1 )
• Hydrogen exists commonly as ( +1 ) but can exist as hydride ( H- ) with an oxidation number of ( -1 )
• Oxygen when in peroxides has an oxidation number of ( -1 )

Question 27

What is a disproportionation reaction ?

Answer 27

A reaction in which a compound undergoes oxidation as well as reduction ( it both increases and decreases in oxidation number )