Topic 8 - Acids, Bases and Salts

Question 1

What is a base?

Answer 1

Bases are proton (H+) acceptors.

Question 2

Is a base soluble?

Answer 2

Bases can either be soluble or insoluble in water. A soluble base is an alkali.

Question 3

What is an alkali?

Answer 3

Soluble bases are known as alkalis, which are substances that release hydroxide (OH-) ions in aqueous solutions.

Question 4

Examples of alkalis?

Answer 4

Alkalis are typically metal hydroxides.

Question 5

Examples of bases?

Answer 5

Bases are typically metal oxides and metal carbonates.

Question 6

What is the pH scale?

Answer 6

The pH scale is used to measure a substance’s ability to donate or accept a proton (H+).

Question 7

What is an acid?

Answer 7

Acids are proton (H+) donors.

Question 8

Examples of acids?

Answer 8

Nitric acid, sulfuric acid, hydrochloric acid

Question 9

What do acids form in water?

Answer 9

Acids form hydrogen (H+) ions when they dissolve in water.

Question 10

What do bases form in water?

Answer 10

Bases form hydroxide (OH-) ions when they dissolve in water.

Question 11

What pH is acidic?

Answer 11

<7

Question 12

What pH is neutral?

Answer 12

7

Question 13

What pH is basic?

Answer 13

> 7

Question 14

What is a strong acid?

Answer 14

An acid with a high ability to donate H+ ions and fully ionises in water e.g. Hydrochloric Acid.

Question 15

What is a weak acid?

Answer 15

An acid with a low ability to donate H+ ions that doesn’t fully ionise in water e.g. Ethanoic Acid.

Question 16

What is a strong base?

Answer 16

A base with a high ability to accept H+ ions that fully ionises in aqueous solutions e.g. Sodium/Potassium Hydroxide.

Question 17

What is a weak base?

Answer 17

A base with a low ability to accept H+ ions that doesn’t fully ionise in aqueous solutions e.g. Ammonia.

Question 18

What is ionisation?

Answer 18

Ionisation is the forming of ions, usually when reacting with water.

Question 19

What is a concentrated acid?

Answer 19

Concentrated acids have a high number of moles of H+ ions per unit volume.

Question 20

What is a dilute acid?

Answer 20

Dilute acids have a low number of moles of H+ ions per unit volume.

Question 21

What is a concentrated base?

Answer 21

Concentrated bases have a high number of moles of OH- ions per unit volume.

Question 22

What is a dilute base?

Answer 22

Dilute bases have a low number of moles of OH- ions per unit volume.

Question 23

What are indicators?

Answer 23

Substances that change colour when they are added to acidic or basic solutions e.g. Litmus Paper

Question 24

What colour is Litmus Paper in acids?

Answer 24

Red

Question 25

What colour is Litmus Paper in bases?

Answer 25

Blue

Question 26

What colour is Litmus Paper in neutral?

Answer 26

Violet

Question 27

What colour is Methyl Orange in acids?

Answer 27

Red

Question 28

What colour is Methyl Orange in bases?

Answer 28

Yellow

Question 29

What colour is Methyl Orange in neutral?

Answer 29

Yellow

Question 30

What is the equation for the reaction between metals and acids?

Answer 30

Metal + Acid ---> Salt + Hydrogen

Question 31

What does hydrochloric acid become when it reacts with a metal?

Answer 31

A Metal Chloride.

Question 32

What does sulfuric acid become when it reacts with a metal?

Answer 32

A Metal Sulfate.

Question 33

What does nitric acid become when it reacts with a metal?

Answer 33

A Metal Nitrate.

Question 34

What is the equation for the reaction between metal oxides and acids?

Answer 34

Acid + Metal Oxide ---> Salt + Water

Question 35

What is the equation for the reaction between metal hydroxides (alkalis) and acids?

Answer 35

Acid + Metal Hydroxide ---> Salt + Water

Question 36

What is the equation for the reaction between metal carbonates and acids?

Answer 36

Acid + Metal Carbonate ---> Salt + Water + Carbon Dioxide

Question 37

What is a neutralisation reaction?

Answer 37

When an acid and alkali react, yielding a salt and water.

Question 38

What is the equation for the heated reaction between ammonium salts and bases?

Answer 38

Base + Ammonium Salt ---> Salt + Ammonia + Water

Question 39

What compound creates a colour change when it reacts?

Answer 39

Copper Sulfate

Question 40

Separating Mixtures Practical - Step 1

Answer 40

Use a Bunsen burner to gently warm the acid.

Question 41

Separating Mixtures Practical - Step 2

Answer 41

Add the insoluble solid (with stirring) until the reaction no longer happens.

Question 42

Separating Mixtures Practical - Step 3

Answer 42

Filter the solution to remove the excess insoluble solid and leave a solution of the salt dissolved in water.

Question 43

Separating Mixtures Practical - Step 4

Answer 43

Heat the solution in an evaporating basin above a beaker of water. The 'water bath' ensures gentle heating.

Question 44

Separating Mixtures Practical - Step 5

Answer 44

Let the solution cool and allow more water to evaporate. As water evaporates, the solution will become more concentrated and the salt will begin to crystallise.

Question 45

What is universal indicator?

Answer 45

The indicator changes to a particular colour depending on the pH of a solution.

Question 46

What is a pH probe?

Answer 46

The probe returns a number that represents the pH of a solution.

Question 47

Specifically, what is the pH scale a measure of?

Answer 47

The numerical pH scale is a measure of the concentration of H+ ions in a solution. For every increase of 1 in pH, the concentration of H+ ions gets divided by 10.

Question 48

What is the ionic equation for a neutralisation reaction?

Answer 48

H+(aq) + OH-(aq) ---> H2O(l)

Question 49

What is titration?

Answer 49

Titration is a technique that measures the volumes of acid and base solutions that are needed in a neutralisation reaction.

Question 50

What are the variables of titration?

Answer 50

The concentration of the acid to be added and the volume of the base.

Question 51

What colour is Phenolphthalein in acids?

Answer 51

Colourless

Question 52

What colour is Phenolphthalein in bases?

Answer 52

Pink

Question 53

Which point of neutralisation reactions do titration indicators help us see?

Answer 53

End-point

Question 54

In titration calculations, what unit is concentration measured in?

Answer 54

Moles/dm3

Question 55

In titration calculations, what unit is volume measured in?

Answer 55

Dm3

Question 56

What is the equation to find concentration?

Answer 56

Number of moles/Volume

Question 57

What is the equation to find the number of moles?

Answer 57

Concentration x Volume

Question 58

What is the equation to find volume?

Answer 58

Number of moles/Concentration

Question 59

1 dm3 is equal to how many cm3?

Answer 59

1000

Question 60

Titration Calculations - Step 1

Answer 60

Write down the balanced symbol equation of the equation. Work out the ratio of reactants.

Question 61

Titration Calculations - Step 2

Answer 61

Divide the volume by 1000 if it's in cm3. Then, work out how many moles of the known substance you have using the formula n=cV.

Question 62

Titration Calculations - Step 3

Answer 62

The number of moles for either substance follows the ratio found in Step 1. Complete any calculations necessary.

Question 63

Titration Calculations - Step 4

Answer 63

Work out the concentration/volume of the "unknown" substance using the equation c=n/V or V=n/c .

Question 64

What can be seen when a metal carbonate and an acid react?

Answer 64

Effervescence

Question 65

Which compound is used to test for sulfates?

Answer 65

Barium Chloride

Question 66

How can you test for sulfates?

Answer 66

Add Barium Chloride. If a white precipitate of Barium Sulfate is seen then a displacement reaction has happened.

Question 67

How do you separate a sulfate test?

Answer 67

Filter through filter paper, wash with distilled water and dry.