Bases

Question 1

Define base

Answer 1

A base is a substance that reacts with an acid to form a salt and water only

Question 2

Define alkali

Answer 2

Alkalis are bases that dissociate in water to produce hydroxide ions, OH-

Question 3

Define strong alkali

Answer 3

A strong alkali completely dissociates in water to give hydroxide ions

Question 4

What are physical properties of alkali

Answer 4

Bitter, soapy, turns red litmus paper blue, can conduct electricity

Question 5

Reaction between alkali and ammonium salt

Answer 5

Alkali + Ammonium salt –> salt+ ammonia gas + water

Question 6

What are observations when ammonium salt is warmed with alkali

Answer 6

Colourless and pungent gas is produced. Gas turns moist red litmus paper blue, gas is ammonia

Question 7

Why does moist red litmus paper turn blue when ammonia gas is in contact with it

Answer 7

Ammonia dissociates in water to produce hydroxide ions which turn red litmus paper blue

Question 8

State the reaction that occurs during precipitation using base

Answer 8

Solution containing metal ion + alkali –> insoluble metal hydroxide +salt

Question 9

Define precipitation

Answer 9

Precipitation is a chemical reaction between which an insoluble product is formed when two aqueous solutions are mixed

Question 10

What happens during neutralisation between acid and an alkali

Answer 10

Acid + Alkali –> Salt + Water

Question 11

Define pH

Answer 11

pH is a measure of acidity or alkalinity in aqueous solution

Question 12

What does pH measure

Answer 12

pH measures the concentration of hydrogen ions in the aqueous solution and is numbered between 0 to 14.

Question 13

Name three strongly acidic substances

Answer 13

hydrochloric acid, nitric acid, sulfuric acid

Question 14

Name three weakly acidic substances

Answer 14

Carbonic acid, ethanoic acid, phosphuric acid

Question 15

Name a neutral substance

Answer 15

Water/aqueous sodium chloride

Question 16

Name three weakly alkaline substances

Answer 16

Aqueous sodium carbonate, aqueous sodium bicarbonate, aqueous ammonia

Question 17

Name two strongly alkaline substances

Answer 17

Aqueous sodium hydroxide, aqueous potassium hydroxide

Question 18

Define an indicator

Answer 18

An indicator is an organic compound which changes colour in accordance with the pH of the solution

Question 19

What are two advantages of using a pH meter over indicators

Answer 19

More reliable and accurate, can be used in data logging to record rapid changes in pH

Question 20

Why should a farmer not add calcium hydroxide and ammonium nitrate into the soil at the same time for his plants?

Answer 20

Slaked lime will react with ammonium nitrate to produce ammonia gas which will escape into the air. This will result in the loss of nitrogen content from the fertiliser to the soil

Question 21

Properties of acidic oxides

Answer 21

• are oxides of non-metals
• usually dissolve and react with water to produce acids
• react with alkalis

Question 22

Properties of basic oxides

Answer 22

• oxides of metals
• if soluble, dissolve and react with water to produce alkalis
• react with acids

Question 23

Properties of amphoteric oxides

Answer 23

• are oxides of metals
• do not dissolve in water
• can behave as acidic oxides or basic oxides

Question 24

Properties of neutral oxides

Answer 24

• oxides of non-metals
• do not dissolve in water
• do not react with acids or alkalis

Question 25

Name 4 acidic oxides

Answer 25

sulfur dioxide, carbon dioxide, nitrogen dioxide, phosphorus(V) oxide

Question 26

State type of oxide of dinitrogen monoxide and nitrogen monoxide

Answer 26

Neutral oxides