Acids, Bases & Salts

Question 1

What is produced when an acid reacts with a metal?

Answer 1

When an acid reacts with a metal, it produces a salt and hydrogen gas.

Question 2

What is an alkali?

Answer 2

An alkali is a water-soluble base.

Question 3

What colour does litmus paper turn in acidic conditions?

Answer 3

In acidic conditions, litmus paper turns red.

Question 4

Why is litmus not suitable for titrations?

Answer 4

Litmus is not suitable for titrations because its color change is not sharp and it goes through a purple transition color in neutral solutions.

Question 5

What is an indicator?

Answer 5

An indicator is a substance that changes colour in acidic or alkaline conditions, used to determine the pH of a solution.

Question 6

Define the term neutralisation.

Answer 6

A neutralisation reaction is a reaction between an acid and a base to form a salt and water.

Question 7

Name the products formed from the reaction between sodium hydroxide and hydrochloric acid.

Answer 7

The products formed from the reaction between sodium hydroxide and hydrochloric acid are sodium chloride and water.

Question 8

What is the general equation for the reaction of a metal carbonate with an acid?

Answer 8

metal carbonate + acid ⟶ salt + carbon dioxide + water

Question 9

What determines the identity of the salt produced in an acid-base neutralisation reaction?

Answer 9

The identity of the salt produced depends on the acid used and the positive ions in the base.

Question 10

What substances act as bases in acid-base reactions?

Answer 10

Metal oxides, metal hydroxides and metal carbonates act as bases in acid-base reactions.

Question 11

Which ions causes a substance to be acidic?

Answer 11

The ion that causes a substance to be acidic is a hydrogen ion / H+.

Question 12

Which ions causes a substance to be alkaline?

Answer 12

The ion that causes a substance to be alkaline is a hydroxide ion / OH-.

Question 13

What pH is classed as neutral?

Answer 13

pH 7 is classed as neutral.

Question 14

What pH range is classed as alkaline?

Answer 14

The pH range for alkaline is 8-14.

Question 15

What pH range is classed as acidic?

Answer 15

The pH range for an acid is 0-6.

Question 16

What is the pH of distilled water?

Answer 16

The pH of distilled water is 7.

Question 17

Describe how to use universal indicator to test the pH of a substance.

Answer 17

Add a few drops of universal indicator solution to the substance.

Check the colour against a colour chart to determine the pH value.

Question 18

What is a proton donor?

Answer 18

A proton donor is an acid that ionises in solution producing protons (H+ ions).

Question 19

What is a proton acceptor?

Answer 19

A proton acceptor is a base that accepts protons donated by an acid.

Question 20

Define strong acid.

Answer 20

A strong acid is an acid that completely dissociates (or ionises) in water, producing solutions of a very low pH.

Question 21

Define weak acid.

Answer 21

A weak acid is an acid that partially dissociates (or ionises) in water, producing pH values closer to the middle of the pH scale, while still being below 7.

Question 22

What is an example of a weak acid?

Answer 22

propanoic acid

Question 23

Define concentrated solution.

Answer 23

A concentrated solution is a solution that contains a higher number of solute molecules per dm3 of solution.

Question 24

What is an oxide?

Answer 24

An oxide is a compound made from one or more atoms of oxygen combined with one other element.

Question 25

What is an acidic oxide?

Answer 25

An acidic oxide is an oxide formed when a non-metal element combines with oxygen, reacting with bases to form a salt and water.

Question 26

What is a basic oxide?

Answer 26

A basic oxide is an oxide formed when a metal element combines with oxygen, reacting with acids to form a salt and water.

Question 27

What type of solution do acidic oxides produce when dissolved in water?

Answer 27

Acidic oxides produce an acidic solution with a low pH when dissolved in water.

Question 28

What type of solution do basic oxides produce when dissolved in water?

Answer 28

Basic oxides produce a basic solution with a high pH when dissolved in water.

Question 29

What is an amphoteric oxide?

Answer 29

An amphoteric oxide is an oxide that can behave as both acidic and basic, depending on whether the other reactant is an acid or a base.

Question 30

Give two examples of amphoteric oxides.

Answer 30

Two examples of amphoteric oxides are zinc oxide (ZnO) and aluminium oxide (Al2O3).

Question 31

Why is the insoluble base added in excess during the preparation of a soluble salt?

Answer 31

The insoluble base is added in excess to ensure that all of the acid has reacted.

Question 32

What step is taken to remove the excess insoluble base after the reaction?

Answer 32

The excess insoluble base is removed by filtration.

Question 33

What is left in the solution after the excess base is removed?

Answer 33

After removing the excess base, only the salt and water remain in the solution.

Question 34

Define the term insoluble base.

Answer 34

An insoluble base is a base that does not dissolve in water.

Question 35

How are crystals produced from a salt solution?

Answer 35

The solution is heated gently and then left to cool.

Question 36

Name the method used to prepare a soluble salt from an acid and alkali.

Answer 36

The method used to prepare a soluble salt from an acid and alkali is titration.

Question 37

Why is an indicator used during the preparation of a soluble salt by titration?

Answer 37

An indicator will indicate when neutralisation has occured.

Question 38

Define precipitation reaction.

Answer 38

A precipitation reaction is a reaction where an insoluble solid (precipitate) is formed from two soluble reactants

Question 39

What is meant by a precipitate?

Answer 39

A precipitate is an insoluble solid that is formed from a reaction between two soluble reactants.

Question 40

Why is the precipitate washed with distilled water?

Answer 40

The precipitate is washed with distilled water to remove traces of the solutions it was made from.

Question 41

Give three examples of insoluble sulfates.

Answer 41

barium sulfate calcium sulfate lead(II) sulfate

Question 42

Give an example of a soluble hydroxide.

Answer 42

sodium hydroxide potassium hydroxide calcium hydroxide

Question 43

Define a hydrated substance.

Answer 43

A hydrated substance is one which is chemically combined with water.

Question 44

Define an anhydrous substance.

Answer 44

An anhydrous substance is a substance containing no water.

Question 45

Define water of crystallisation.

Answer 45

Water of crystallisation refers to the water molecules present in a hydrated substance.