2b.3 - Acids, Alkalis and Bases

Question 1

What does the pH scale go up to?

Answer 1

pH 14

Question 2

What makes an acid an acid?

Answer 2

H+ ions

Question 3

What is a base?

Answer 3

A substance with a pH greater than 7

Question 4

What is an alkali?

Answer 4

A base dissolved in water

Question 5

What makes an alkali an alkali?

Answer 5

OH- ions

Question 6

What is the word equation for neutralisation?

Answer 6

acid + base -> salt + water

Question 7

What is the symbol equation for neutralisation in terms of H+ and OH- ions?

Answer 7

H+ + OH- -> H2O

Question 8

Write the word equation for the reaction of acids and metals

Answer 8

acid + metal -> salt + hydrogen

Question 9

What is the test for hydrogen?

Answer 9

Squeaky pop

Question 10

Why do copper, silver, gold and platinum not react with dilute acid?

Answer 10

They are less reactive than hydrogen

Question 11

What type of salts are produced when hydrochloric acids are reacted with metals?

Answer 11

Chloride salts

Question 12

What type of salts are produced when sulfuric acids are reacted with metals?

Answer 12

Sulfate salts

Question 13

What type of salts are produced when nitric acids are neutralised?

Answer 13

Nitrate salts

Question 14

Give examples of bases

Answer 14

• Metal oxides

- Metal hydroxides

Question 15

What is produced when you react hydrochloric acid with copper oxide?

Answer 15

Copper chloride and water

Question 16

What is produced when you react hydrochloric acid with sodium hydroxide?

Answer 16

Sodium chloride and water

Question 17

What is produced when you react sulfuric acid with zinc oxide?

Answer 17

Zinc sulfate and water

Question 18

What is produced when you react sulfuric acid with calcium hydroxide?

Answer 18

Calcium sulfate and water

Question 19

What is produced when you react nitric acid with magnesium oxide?

Answer 19

Magnesium nitrate and water

Question 20

What is produced when you react nitric acid with potassium hydroxide?

Answer 20

Potassium nitrate and water

Question 21

What is the chemical formula of ammonia?

Answer 21

NH3

Question 22

What is the word equation for the neutralisation of ammonia?

Answer 22

ammonia + nitric acid -> ammonium nitrate

Question 23

Why is the neutralisation of ammonia different from most other neutralisation reactions?

Answer 23

There is no water produced - just the ammonium salt

Question 24

Why is ammonium nitrate a good fertiliser?

Answer 24

It has nitrogen from two sources, the ammonia and nitric acid and plants need nitrogen to make proteins

Question 25

How do you make a soluble salt using a metal or an insoluble base? (5)

Answer 25

• Add the metal or insoluble base the acid
• The solid will dissolve in the acid as it reacts
• Excess solid will sink to the bottom of the flask
• Filter the excess metal
• Crystallise it

Question 26

How do you make soluble salts using an alkali? (3)

Answer 26

• You need to know exactly the right amount of alkali to neutralise the acid - you use an indicator
• Then repeat using exactly the same volumes of acid and alkali so the salt isn’t contaminated with indicator
• Then crystallise as normal

Question 27

How do you crystallise when making soluble salts? (the last step)

Answer 27

Evaporate some water then leave it to evaporate slowly. This is crystallisation.

Question 28

What do you need to do if the salt you are trying to make is insoluble?

Answer 28

Use a precipitation reaction

Question 29

How do you do a precipitation reaction? (2)

Answer 29

• Pick two solutions that contain the ions you need (e.g to make lead chloride you need a solution with lead ions and chloride ions. You can use lead nitrate (most nitrates are soluble) solution with sodium (all group one compounds are soluble) chloride solution
• Filter it, wash it and dry it

Question 30

Other than making insoluble salts, what else are precipitation reactions used for?

Answer 30

Removing poisonous ions from drinking water and making water softer