9.2 Acid-alkali Indicators And pH Scale

Question 1

What’s the use of indicators?

Answer 1

We can use indicators to show the presence of acids and alkalis.

Question 2

What’s a natural indicator?

Answer 2

Indicators that can be extracted from plants in Nature.

Question 3

What’s the essential of a natural indicator? What’s it’s use?

Answer 3

Pigments. It change color when mixed with acids or alkalis.

Question 4

What’s litmus?

Answer 4

Litmus is a mixture of pigments extracted from lichen.

Question 5

What forms of litmus have in laboratory?

Answer 5

Solution and paper form.

Question 6

Compare when blue and red litmus paper touches acid or alkali.

Answer 6

Blue -> red \ Touching Acid
Red -> blue \ Touching Alkali

Question 7

What’s a universal indicator?

Answer 7

A universal indicator is a mixture of several indicators.

Question 8

On pH scale, distinguish acidic substance, alkaline substance, and natural substance’s pH value.

Answer 8

Acidic substance< 7
Alkaline substance> 7
Natural substance= 7

Question 9

Show the vague colour range of pH value.

Answer 9

Red, orange, yellow, green, blue.

Question 10

What’s the advantages and disadvantages of pH meter?

Answer 10

Pros:
-More accurate
-Can be reused
-Can be used to measure the pH value of a liquid with a deep colour.
Cons:
-More expensive
-Larger size, less convenient to carry around