Multiple Choice Questions
Question 1: The correct way of making a solution of acid in water is to
(a) add water to acid.
(b) add acid to water.
(c) mix acid and water simultaneously.
(d) add water to acid in a shallow container.
Solution 1: (b) add acid to water.
If we apply water to the acid, it will be an exothermic reaction that will create a lot of heat that will lead to an explosion. Water can, however, be applied to the acid.
Question 2: Products of a neutralisation reaction are always
(a) an acid and a base.
(b) an acid and a salt.
(c) salt and water.
(d) a salt and a base.
Solution 2: (c) salt and water.
In a neutralisation reaction the products we get are salt and water.
Question 3: 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 the base.
(c) Pink in acid and yellow in the base.
(d) Red in acid and blue in the base.
Solution 3: (b) Yellow in acid and red in the base.
Turmeric paste is yellow in colour and is acidic in nature, so it retains yellow in acid, while the base neutralization turns it to red.
Question 4: 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
Solution 4: (d) colourless and pink
Phenolphthalein is a synthetic indicator and its colour in acidic solutions is colourless and in basic solutions is pink.
Question 5: When the soil is too basic, plants do not grow well in it. To improve its quality what must be added to the soil?
(a) Organic matter
(b) Quick lime
(c) Slaked lime
(d) Calamine solution
Solution 5: (a) Organic matter
In order to neutralize the foundation, organic matter is applied to the essential soil, which increases its consistency.
Question 6: ‘Litmus’, a natural dye is an extract of which of the following?
(a) China rose (Gudhal)
(b) Beetroot
(c) Lichen
(d) Blueberries (Jamun)
Solution 6: (c) Lichen
Litmus is a natural dye in an extract of Lichen.
Question 7: A neutralisation reaction is a
(a) physical and reversible change.
(b) a physical change that cannot be reversed.
(c) chemical and reversible change.
(d) the chemical change that cannot be reversed.
Solution 7: (d) chemical change that cannot be reversed.
It is a chemical reaction where the acid and the base react quantitatively with each other. An inevitable mechanism is neutralization.
Question 8: A solution changes the colour of turmeric indicator from yellow to red. The solution is
(a) basic
(b) acidic
(c) neutral
(d) either neutral or acidic
Solution 8: (a) basic
Turmeric is acidic in nature and is thus turned to red because of the base's neutralization.
Question 9: Which of the following set of substances contain acids?
(a) Grapes, lime water
(b) Vinegar, soap
(c) Curd, milk of magnesia
(d) Curd, vinegar
Solution 9: (d) Curd, vinegar
Vinegar contains acetic acid and Curd contains lactic acid.
Question 10: On adding phenolphthalein indicator to a colourless solution, no change is observed. What is the nature of this solution?
(a) Basic
(b) Either acidic or basic
(c) Either acidic or neutral
(d) Either basic or neutral
Solution 10: (c) Either acidic or neutral
For an acidic or neutral solution, the phenolphthalein indicator colour will not change.
Question 11: Which of the following is an acid-base indicator?
(a) Vinegar
(b) Lime water
(c) Turmeric
(d) Baking soda
Solution 11: (c) Turmeric
The turmeric in the acid solution is yellow and in the base solution is red.
Very Short Answer Questions..............
Question 12: Look at the given reaction.
Hydrochloric acid + Sodium hydroxide (base) → Sodium chloride (salt) + Water
Sodium chloride formed in this reaction remains in solution form. Can we get solid sodium chloride from this solution? Suggest a method (if any).
Solution 12: Sodium chloride is soluble in water, so we have a sodium chloride solution. Via an evaporation process, we can get solid sodium chloride.
Question 13: State whether the following statements are true or false. Correct the false statements.
(a) All substances are either acidic or basic.
(b) A compound if acidic will turn all indicators red.
(c) Lime water turns red litmus blue.
(d) Common salt dissolved in water turns blue litmus red.
(e) Phenolphthalein is a natural indicator.
(f) Calamine can be used to treat ant’s sting.
(g) Lemon water is basic in nature.
Solution 13:
- False- Substances in nature can be acidic, basic or neutral.
- False- Acids don’t turn red colour of all indicators.
- True
- False- There will be no improvements in the colour of the litmus paper.
- False- Phenopthalein is a human-made indicator.
- True
- False- Water of lemon is acidic in nature.
Question 14: Paheli is suffering from indigestion due to acidity. Is it advisable to give her orange juice in this situation and why?
Solution 14: No, As orange juice is acidic in nature, orange juice is not recommended.
Short Answer Questions..............
Question 15: Look at Figure 5.1 which shows solutions taken in test tubes A, B, C and D. What colour is expected when a piece of red litmus paper is dropped in each test tube? Nature of the solutions is given in the table for your help.
Solution 15:
Question 16: While playing in a park, a child was stung by a wasp. Some elders suggested applying the paste of baking soda and other lemon juice as the remedy. Which remedy do you think is appropriate and why?
Solution 16: When a wasp stings, it pushes a liquid fluid into the body. This product is acidic in nature, so baking soda can be used as a treatment and the discomfort and redness can be intensified by adding lemon juice.
Question 17: Form a sentence using the following words – baking soda, ant bite, moist, effect, neutralised, rubbing.
Solution 17: Rubbing the moist baking soda will neutralize the effect of an ant bite.
Question 18: Match the substances in Column I with those in Column II.
Solution 18:
Question 19: Fill the blanks in the following sentences:
(a) Lemon juice and vinegar taste ___________ because they contain ___________.
(b) Turmeric and litmus are _________ acid-base indicators.
(c) Phenolphthalein gives _________ colour with lime water.
(d) When an acidic solution is mixed with a basic solution, they _________ each other forming _________ and water.
Solution 19:
(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 and water.
Long Answer Questions...............
Question 20: Boojho, Paheli and their friend Golu were provided with a test tube each containing China rose solution which was pink in colour. Boojho added two drops of solution ‘A’ in his test tube and got a dark pink colour. Paheli added 2 drops of solution ‘B’ to her test tube and got green colour. Golu added 2 drops of solution ‘C’ but could not get any change in colour. Suggest the possible cause for the variation in their results.
Solution 20: Since solution A transforms the rose colour of China into dark pink, solution A is also an acidic solution. Solution B transforms the rose colour of China to green, so Solution B is a basic solution. It is a neutral solution, because Solution C did not affect the colour of the Chinese rose solution.
Question 21: Fill in the crossword given as Figure 5.2 with the help of the clues provided.
Across
(2) The solution which does not change the colour of either red or blue litmus.
(4) Phenolphthalein gives pink colour in this type of solution.
(7) Colour of blue litmus in lemon juice.
Down
(1) It is used to test whether a substance is acidic or basic.
(3) It is a natural indicator and gives a pink colour in a basic solution.
(5) Nature of ant’s sting.
(6) It is responsible for the increase in temperature during a neutralisation reaction.
Solution 21:
Across
(2) The solution which does not change the colour of either red or blue litmus: Neutral
(4) Phenolphthalein gives pink colour in this type of solution: Base
(7) Colour of blue litmus in lemon juice: Red
Down
(1) It is used to test whether a substance is acidic or basic: Indicator
(3) It is a natural indicator and gives a pink colour in a basic solution: Turmeric
(5) Nature of ant’s sting: Acidic
(6) It is responsible for the increase in temperature during a neutralisation reaction: Heat
Question 22: A farmer was unhappy because of his low crop yield. He discussed the problem with an agricultural scientist and realised that the soil of his field was either too acidic or too basic. What remedy would you suggest the farmer to neutralise the soil?
Solution 22: It is treated with bases such as rapid lime (calcium oxide) or slaked lime if the soil is too acidic (calcium hydroxide). If the ground is too basic, it is applied to it with organic matter. Acids which neutralize the basic nature of the soil are released by organic matter.
Question 23: You are provided with four test tubes containing sugar solution, baking soda solution, tamarind solution, salt solution. Write down activity to find nature (acidic/basic/neutral) of each solution.
Solution 23: For test tubes containing sugar solution, baking soda solution, tamarind solution, salt solution, apply blue litmus solution and then red litmus solution. In order to find the essence of each of them, one should note the color variations. It's just as follows.
(i) As there is no color change, the sugar and salt solution is neutral.
(ii) Baking soda transforms to blue with red litmus and is a simple remedy.
(iii) Blue litmus transforms to red tamarind solution and it is acidic in nature.
Question 24: You are provided with three test tubes A, B and C as shown in Figure 5.3 with different liquids. What will you observe when you put
(a) a piece of blue litmus paper in each test tube.
(b) a piece of red litmus paper in each test tube.
(c) a few drops of phenolphthalein solution to each test tube.
Solution 24:
Question 25: Paheli observed that most of the fish in the pond of her village were gradually dying. She also observed that the waste of a factory in their village is flowing into the pond which probably caused the fish to die.
(a) Explain why the fish were dying.
(b) If the factory waste is acidic in nature, how can it be neutralised?
Solution 25:
a) Since factory waste is disposed of in the water, it can destroy the fish as acids, bases and other poisonous substances can be found in factory waste.
b) It may be neutralized by adding basic compounds if the factory waste is acidic in nature.
Question 26: Explain two neutralisation reactions related to a daily life situation.
Solution 26:
A) Acidity
Acidity is caused in the stomach when indigestion produces a lot of acids. This can be managed by taking antacids like milk of magnesia.
(b) Ant’s sting
The Ant's bite releases the skin with formic acid. It may be neutralized by rubbing or placing calamine lotion with baking soda.