Question

A. STATE WHETHER THE FOLLOWING STATEMENTS ARE TRUE OR FALSE.
CORRECT THE FALSE STATEMENTS.
(a) All substances are either acidic or basic.
False. Substances can be neutral as well.
(b) A compound if acidic will turn all indicators red.
False. Acids do not turn all indicators red.
(c) Lime water turns red litmus blue.
True.
(d) Common salt dissolved in water turns blue litmus red.
False. It does not change the colour of litmus at all.
(e) Phenolphthalein is a natural indicator.
False. It is a man-made indicator.
(f) Lemon water is basic
True
(a) Lemon juice and vinegar taste sour because they contain acids.
(b) Turmeric and litmus are natural acid-base indicators.
(c) Phenolphthalein gives pink colour with lime water.
(d) When an acidic solution is mixed with a basic solution, they neutralize each other forming salt.
C. ANSWER THE FOLLOWING-
1. What are bases? What are their physical properties?
Answer. Bases taste bitter, feel slippery, It conduct electricity when dissolved in water. Indicator compounds such as litmus can be used to detect bases. Bases turn red litmus paper blue.
2. Give two uses of each.
a.Calcium hydroxide
b. Ammonium hydroxide
Answer. Calcium hydroxide has many industrial uses, such as in the Kraft paper process, as a flocculent in water and sewage treatment, ammonia preparation, and as a pH modifier. It is also an important ingredient in cement, plaster and mortars.
3. What is an acid-base indicator? Give one example.
Answer: Acid-base indicators are special substances that are used to detect the acidity or basicity of other substances. The change in colour of the indicators helps us in understanding which substance is acidic and which one is basic. Example: Litmus paper is a natural acid-base indicator.
4. Name the base used to manufacture the soap.
Answer. Sodium hydroxide (caustic soda) is used in the manufacture of soap.
D. MULTIPLE CHOICE QUESTIONS:
1. Turmeric is a natural indicator. On adding its paste to acid and base separately, which colours would
be observed
(a) Yellow in both acid and base.
(b) Yellow in acid and red in base.
(c) Pink in acid and yellow in base.
(d) Red in acid and blue in base.
2. Phenolphthalein is a synthetic indicator and its colours in acidic and basic solutions, respectively are
(a) Red and blue.
(b) Blue and red.
(c) Pink and colourless.
(d) Colourless and pink
3. Litmus’, a natural dye is an extract of which of the following?
(a) China rose (Gudhal)
(b) Beetroot
(c) Lichen
(d) Blueberriesacid-base (Jamun)
4. A solution changes the colour of the turmeric indicator from yellow to red. The solution is
(a) Basic
(b) Acidic
(c) Neutral
(d) Either neutral or acidic
5. Which of the following is an acid-base indicator?
(a) Vinegar
(b) Lime water
(c) Turmeric
(d) Baking soda

Answer 1

Answer:

question3) ( c) Lichen

question 4) (a) Basic

Answer 2

Explanation:

Litmus is a natural indicator.

(1 Point)

True

False