Chemical Changes

Question 1

What ions are acids sources of?

Answer 1

H+ ions

Question 2

What ions are alkalis sources of?

Answer 2

OH- ions

Question 3

What is the pH of a neutral solution?

Answer 3

7

Question 4

What is the pH of an acidic solution?

Answer 4

Less than 7

Question 5

What is the pH of an alkaline resolution?

Answer 5

Greater than 7

Question 6

What are the effects of acids, alkalis and neutral solutions on litmus?

Answer 6

Acid - red
Neutral - purple
Alkali - blue

Question 7

What are the effects of acids, alkalis and neutral solutions on Universal Indicator?

Answer 7

A spectrum from red strong acid to green neutral to purple strong alkali

Question 8

What are the effects of acids, alkalis and neutral solutions on methyl orange?

Answer 8

Acid - red
Neutral - yellow
Alkali - yellow

Question 9

What are the effects of acids, alkalis and neutral solutions on phenolphthalein?

Answer 9

Acid - colourless
Neutral - colourless
Alkali - pink

Question 10

How does the pH change as the concentration of hydrogen ions increases?

Answer 10

It decreases, becomes more acidic

Question 11

How does the pH change as the concentration of hydroxide ions increases?

Answer 11

It increases, becomes more alkaline

Question 12

As the pH of a solution decreases by 1, the concentration of hydrogen ions increases by a factor of what?

Answer 12

10

Question 13

What makes an acid concentrated/dilute?

Answer 13

The concentration of an acid basically refers to how watered down it is. The more watered down, the less concentrated, the more dilute.

Question 14

What makes an acid strong?

Answer 14

The strength of an acid depends on how much it ionises (splits up to produce hydrogen ions) in water. The more ionisation, the stronger.

Question 15

What is a base?

Answer 15

Any substance that reacts with an acid to form a salt and water (only).

Question 16

What is an alkali?

Answer 16

A soluble base

Question 17

acid + metal oxide =

Answer 17

salt + water

Question 18

acid + metal hydroxide =

Answer 18

salt + water

Question 19

acid + metal =

Answer 19

salt + hydrogen

Question 20

acid + metal carbonate =

Answer 20

salt + water + carbon dioxide

Question 21

What is the chemical test for hydrogen?

Answer 21

Hydrogen makes a ‘squeaky pop’ with a lit splint.

Question 22

What is the chemical test for carbon dioxide?

Answer 22

Carbon dioxide makes limewater turn cloudy.

Question 23

What is a neutralisation reaction?

Answer 23

A reaction between an acid and a base

Question 24

In a neutralisation reaction, what ions react to make water?

Answer 24

H+ and OH- ions

Question 25

Name the three main stages of making a soluble salt using an acid and an insoluble base and explain why they are done

Answer 25

1) Mix the insoluble base into the acid until it is in excess - to make sure all of the acid is reacted
2) Filter off the excess base
3) Leave the solution - to let the water evaporate over time leaving the pure salt

Question 26

Why should you use titration when making a soluble salt from an acid and a soluble base (alkali)?

Answer 26

Using titration, you can make sure there is no excess base and the solution remaining is only the salt and water

Question 27

How do you carry out an acid-alkali titration?

Answer 27

Pg 47 in CGP guide

Question 28

Are nitrates soluble?

Answer 28

Yes, all of them

Question 29

Are chlorides soluble?

Answer 29

Yes, except silver and lead

Question 30

Are sulphates soluble?

Answer 30

Yes, except lead, barium and calcium

Question 31

Are carbonates soluble?

Answer 31

No, except sodium, potassium and ammonium

Question 32

Are hydroxides soluble?

Answer 32

No, except sodium, potassium and ammonium

Question 33

What must the two reactants of a precipitation reaction be?

Answer 33

Soluble salts

Question 34

How do you obtain a pure, dry sample of an insoluble salt?

Answer 34

Pg 46 in CGP guide