Topic 3 - Chemical Changes

Question 1

What is the pH scale?

Answer 1

A measure of how acidic or alkaline a substance is

Question 2

How does a pH probe and metre work?

Answer 2

The pH probe is put into the substance and it electronically measures the pH producing a reading on the metre

Question 3

Why are pH probes more reliable than indicators?

Answer 3

It is more accurate (can go to decimal places) and doesn’t require humans to guess shades of colours

Question 4

What is an alkali?

Answer 4

A base that dissolves in water to form a pH of greater than 7

Question 5

What is an acid?

Answer 5

Any substance that forms an aqueous solution with a pH of less than 7

Question 6

What makes an acidic solution acidic?

Answer 6

The solution will release hydrogen ions in the solution - it will ionise

Question 7

What is a base?

Answer 7

Any substance with a pH of greater than 7

Question 8

What makes a base an alkali?

Answer 8

If it is soluble (can dissolve in water)

Question 9

What makes a solution alkaline?

Answer 9

They form hydroxide ions in water

Question 10

What will a neutralisation reaction produce?

Answer 10

A salt and water

Question 11

What are the 3 main acids and their symbols?

Answer 11

Hydrochloric acid: HCL
Sulfuric acid: H2SO4
Nitric acid: HNO3

Question 12

What are the 2 main bases and their symbols?

Answer 12

Sodium Hydroxide: NaOH
Calcium carbonate: CaCO3

Question 13

What pH does stomach acid typically have?

Answer 13

2

Question 14

What are 3 weak acids and their symbols?

Answer 14

Ethanoic acid: CH3COOH
Citric acid: C6H8O7
Carbonic acid: H2CO3

Question 15

What are 3 strong acids and their symbols?

Answer 15

Hydrochloric acid: HCL
Sulfuric acid: H2SO4
Nitric acid: HNO3

Question 16

What is special about the ionisation of weak acids?

Answer 16

It is reversible

Question 17

What is different between strong and weak acid ionisation?

Answer 17

Strong acids fully ionise and weak acids don’t fully ionise

Question 18

What does it mean if the equilibrium of an ionisation is to the left or right?

Answer 18

If the equilibrium is to the left, there are more unionised molecules of acid and vice versa

Question 19

What is strength concerning acids?

Answer 19

How much it dissociates

Question 20

What is pH?

Answer 20

A measure of the concentration of hydrogen ions in a solution

Question 21

Will a pH of 1 have a higher concentration of hydrogen ions than a pH of 7?

Answer 21

The higher the concentration to hydrogen ions, the lower the pH

Question 22

What does a difference of 1 pH correlate to in terms of concentration of hydrogen ions?

Answer 22

1 pH means 10x more or less concentration of hydrogen ions, depending on whether the pH is increasing or decreasing

Question 23

Where does the position of equilibrium lie for weak acids?

Answer 23

To the left

Question 24

What happens when a metal (hydr)oxide reacts with an acid?

Answer 24

You get a salt and water

Question 25

What happens when a metal carbonate reacts with an acid?

Answer 25

You get salt, water and carbon dioxide

Question 26

Are nitrates soluble?

Answer 26

All nitrates are soluble

Question 27

Are chlorides soluble?

Answer 27

All chlorides except from silver and lead are soluble

Question 28

Are carbonates and hydroxides soluble?

Answer 28

All carbonates and hydroxides are insoluble except for sodium, potassium and ammonium

Question 29

Are salts of sodium, potassium or ammonium soluble?

Answer 29

All common salts of sodium, potassium and ammonium are soluble

Question 30

Are sulfates soluble?

Answer 30

All sulfates except for barium, calcium and lead sulfate are soluble