8a ii. Acids and Bases

Question 1

What does the pH scale measure?

(level 3 )

Answer 1

The acidity or alkalinity of a substance

Question 2

What is the number range of the pH scale?

Answer 2

0-14

Question 3

What is the pH range for acids?

Answer 3

Less than 7

(do NOT say 1-6)

Question 4

What is the pH range for alkalis?

Answer 4

Greater than 7

(do NOT say 8-14)

Question 5

What is a pH “indicator”?

Answer 5

A substance that changes colour in the presence of an acid or alkali.

Question 6

What is the pH value for neutral solutions?

Answer 6

7

Question 7

Name 3 indicators used in the lab

Answer 7

pH paper

universal indicator

red cabbage indicator

Question 8

What does pH measure?

(level 4)

Answer 8

The concentration of H⁺ _(aq) ions in a solution

Question 9

What is the acidic ion?

Answer 9

The H⁺ _(aq) ion

Question 10

Definition of an acid

Answer 10

A solution with a higher concentration of hydrogen (H⁺) ions than hydroxide (OH^-) ions

Question 11

How is concentration of hydrogen ions represented?

Answer 11

By using square brackets

[H⁺ _(aq)]

Question 12

What effect does diluting an acid have on its pH value?

Answer 12

It increases it towards 7

Question 13

What factor of dilution will increase the pH value of an acid by 1?

Answer 13

A dilution factor of 10

( adding 90ml of water to 10 ml of acid to make 100 ml for example)

Question 14

What is the alkali ion?

Answer 14

The OH^- _(aq) ion

Question 15

What makes solutions alkaline?

Answer 15

A solution with higher concentration of hydroxide ions than hydrogen ions

Question 16

What effect does dilution of alkalis have on their pH value?

Answer 16

It decreases it towards 7

Question 17

What factor of dilution will decrease the pH value of an alkali by 1?

Answer 17

A dilution factor of 10

( adding 90ml of water to 10 ml of alkali to make 100 ml for example)

Question 18

Why do neutral solutions a have pH of 7?

Answer 18

Because they have equal concentrations of hydroxide ions and hydrogen ions

Question 19

How is concentration of hydroxide ions represented?

Answer 19

By using square brackets

[OH^- _(aq)]

Question 20

Why can the concentration of OH- (aq) NEVER be zero even with very low pH values?

Answer 20

Because

[H⁺ _(aq)] x [OH^- _(aq)] = a number that is NOT zero

Question 21

What is acid rain?

Answer 21

Rain that falls with a pH below 5.5

Question 22

What are some uses of acids in food industry

Answer 22

• flavourings
• preservatives

Question 23

Which 2 gases are mainly responsible for acid rain?

Answer 23

sulphur dioxide

nitrogen oxides

Question 24

What is an “acidic oxide” ?

Answer 24

A NON-METAL oxide that is soluble in water and lowers the pH below 7.

Question 25

What is an “basic oxide” ?

Answer 25

A METAL oxide that is soluble in water and increases the pH above 7

Question 26

What are the 3 common lab acids?

Answer 26

Hydrochloric acid

Sulphuric acid

Nitric acid

Question 27

What is the molecular formula and the ionic solution formula for hydrochloric acid?

Answer 27

Question 28

What is the molecular formula and the ionic solution formula for sulphuric acid?

Answer 28

Question 29

What is the molecular formula and the ionic solution formula for nitric acid?

Answer 29

Question 30

What are the 3 most common lab alkalis?

Answer 30

Sodium hydroxide

Barium hydroxide

Potassium hydroxide

Question 31

What is the ionic solid and ionic solution formula for barium hydroxide?

Answer 31

Question 32

What is the ionic solid and ionic solution formula for potassium hydroxide?

Answer 32

Question 33

What is the ionic solid and ionic solution formula for sodium hydroxide?

Answer 33