9.2

Question 1

Some plants contain a … which show different colours in acidic and alkaline solutions. These extracts can be used as an … to distinguish between acids and alkalis

Answer 1

pigment, indicator

Question 2

… is a acid- alkali indicator commonly used in the laboratory

Answer 2

Litmus

Question 3

There are two kinds of litmus, what are they

Answer 3

Blue litmus and red litmus

Question 4

What litmus is used to identify acids

Question 5

In … substances, both blue litmus and red litmus do not change colour

Answer 5

Neutral

Question 6

pH values are used to describe

Answer 6

The relative acidity or alkalinity of substances

Question 7

pH value can be measured using … and …

Answer 7

Universal indicator, pH paper, pH indicator

Question 8

Acid in battery

Answer 8

pH 0

Question 9

Acid in stomach

Answer 9

pH 1

Question 10

Lemon juice

Answer 10

pH 2

Question 11

Orange juice

Answer 11

pH3

Question 12

Tomato juice

Answer 12

pH4

Question 13

Black coffee

Answer 13

pH 5

Question 14

Milk

Answer 14

pH6

Question 15

Distilled water

Answer 15

pH7

Question 16

Seawater

Answer 16

pH 8

Question 17

Baking soda solution

Answer 17

pH9

Question 18

Antacid 胃藥

Answer 18

pH10

Question 19

Glass cleaner

Answer 19

pH11

Question 20

Soap solution

Answer 20

pH12

Question 21

Bleach

Answer 21

13

Question 22

Drain cleaner

Answer 22

pH14

Question 23

pH meter is

Answer 23

An electronic instrument used to measure the exact pH values of solutions

Question 24

We have to … before using pH meter

Answer 24

Calibrate

Question 25

Advantage of universal indicator and pH paper

Answer 25

Convenient as no calibration is needed, less solution is needed

Question 26

Disadvantage of using universal indicator or pH paper

Answer 26

Not suitable for dark coloured solutions, cannot be reused, measurement is subjective and less accurate

Question 27

Advantage of pH meter

Answer 27

Suitable for solutions of any colour, can be reused, reading error is a small due to the small interval between readings with the proper calibration, the measured pH value is more accurate

Question 28

Disadvantage of using a pH meter

Answer 28

Calibration is needed so it is less convenient, more solution is needed