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Q1. Grapes contain bases in them.

• 1) False
• 2) True

Solution

False. Grapes contain acid in them.

Q2. What will be the colour change on adding common salt dissolved in water to red litmus paper as well as blue litmus paper?

• 1) Both red and blue litmus papers remain same.
• 2) Red litmus becomes pink.
• 3) Blue litmus becomes red.
• 4) Red litmus becomes blue.

Solution

Common salt is a neutral substance and does not change the colour of both litmus papers.

Q3. Curd tastes sour due to presence of

• 1) Bases
• 2) Acids
• 3) Bacteria
• 4) Milk

Solution

Curd contains lactic acid and since acids are sour in taste so, curd tastes sour.

Q4. What is acid rain? How is it caused? What are its after effects?

Solution

The rain which contains a higher level of acid than normal is called acid rain.   Acid rain is caused by the acidic gases like sulphur dioxide, nitrogen dioxide and carbon dioxide which are released into the air as pollutants during the burning of various types of fuels. Sulphur dioxide gas dissolves in falling rain drops to form sulphuric acid; nitrogen dioxide gas dissolves in rain drops to form nitric acid whereas carbon dioxide gas dissolves in rain drops to form carbonic acid. The presence of sulphuric acid, nitric acid and carbonic acid in rain water makes the rain water acidic and when this acidic rain water falls on the earth, we call it acid rain. Acid rain causes damage to aquatic animals (like fish), trees, crop plants, metal structures and stone buildings and monuments. This happens as follows: (i) Acid rain makes the water of lakes, ponds and rivers too acidic due to which fish and other aquatic animals get killed. (ii) Acid rain eats up the leaves of the trees gradually. By losing leaves, the trees die. Acid rain also damages crop plants in the fields. (iii) Acid rain damages the metal structures like steel bridges, etc., when it falls on them. (iv) Acid rain damages the surfaces of buildings and monuments made of stone.

Q5. If a drop of lime juice is put on red litmus paper, the colour of litmus paper will change to:

• 1) Pink
• 2) Green
• 3) Blue
• 4) Remains the same

Solution

Acids change the colour of blue litmus to red but do not affect the red litmus paper so its colour will remain same.

Q6. What are the different types of salts?

Solution

Following are the main three types of salts: (a) Neutral(b) Acidic(c) Basic

Q7. Which of the following is false about indicators?

• 1) Turmeric is a synthetic indicator
• 2) Litmus is available in form of solution
• 3) Certain indicators are used to test the completion of a chemical reaction.
• 4) Indicators change colour to indicate the presence of some substances.

Solution

Turmeric is a natural indicator.

Q8. Which of these can be used as an indicator?

• 1) Lime water
• 2) Phenolphthalein
• 3) Calamine solution
• 4) Ammonia

Solution

Phenolphthalein is a synthetic indicator used for identifying acids and bases.

Q9. Which of the following contains a base?

• 1) Ant sting
• 2) Antacids
• 3) Oranges
• 4) Vinegar

Solution

Antacids are weak bases. Vinegar contains acetic acid, oranges contain citric acid and ant sting contains formic acid.

Q10. Oxalic acid is present in ________________.

Solution

Oxalic acid is present in spinach.

Q11. Acids have a ____________ taste.

Solution

Acids have a sour taste.

Q12. Fruits like orange and lemon are citrus fruits. If few drops of juice obtained from these citrus fruits are added on blue litmus paper, what colour change will be observed? Explain why?

Solution

Blue litmus paper will become red on treating with juices of citrus fruits because citrus fruits contain acid which turns blue litmus paper red.

Q13. Acetic acid is present in ________________.

Solution

Acetic acid is present in vinegar.

Q14. Lactic acid is present in spinach.

• 1) True
• 2) False

Solution

False. Oxalic acid is present in spinach.

Q15. Turmeric paper becomes red in presence of ______________.

Solution

Turmeric paper becomes red in presence of bases.

Q16. Which of these acids are present in acid rain?

• 1) Carbonic acid
• 2) Nitric acid
• 3) All of above
• 4) Sulphuric acid

Solution

The rain becomes acidic because carbon dioxide, sulphur dioxide and nitrogen dioxide (which are released into the air as pollutants) dissolve in rain drops to form carbonic acid, sulphuric acid and nitric acid respectively

Q17. The acid present in lemon is _____________.

Solution

The acid present in lemon is citric acid.

Q18. Our stomach contains which acid?

• 1) Tartaric acid
• 2) Oxalic acid
• 3) Hydrochloric acid
• 4) Ascorbic acid

Solution

Our stomach contains hydrochloric acid

Q19. Shampoo (dilute solution) turns turmeric paste red.

• 1) True
• 2) False

Solution

True

Q20. What is the taste of a base?

• 1) Bitter
• 2) Sour
• 3) Sweet
• 4) Salty

Solution

Generally all bases are bitter in taste.

Q21. Differentiate between acids and bases (four points).

Solution

Acids Bases 1. They are sour in taste. 1. They are bitter in taste. 2. They give corrosive touch. 2. They give soapy touch. 3. They turn blue litmus to red. 3. They turn red litmus to blue. 4. They have no effect on the colour of phenolphthalein. 4. They turn the colourless phenolphthalein to pink.

Q22. Which of the following base is used as a cleansing agent?

• 1) Ammonium hydroxide
• 2) Calcium hydroxide
• 3) Sodium hydroxide
• 4) Magnesium hydroxide

Solution

Ammonium hydroxide is used as a cleansing agent.

Q23. Which of the following is not a property of acids?

• 1) Acids can be corrosive or non-corrosive.
• 2) Acids are used in soap and detergent industry.
• 3) Acids find use in preparing fertilizers.
• 4) Acids are sour in taste.

Solution

Sodium hydroxide base is used in soap and detergent industry.

Q24. Guava is a rich source of oxalic acid.

• 1) True
• 2) False

Solution

False. Curd is a rich source of oxalic acid.

Q25. Base and water are produced in a neutralisation reaction.

• 1) True
• 2) False

Solution

False. Salt and water are produced in a neutralisation reaction.

Q26. Industrial waste should be neutralised before disposing it into the water bodies. What is the nature of these waste? How are these treated?

Solution

The industrial waste is either too acidic or too basic in nature. This too much acid or base must be neutralised before disposing this waste into water bodies. Too acidic waste can be treated with quicklime or slaked lime and too basic waste can be treated with either acid or acidic waste discharged from some other industry.

Q27. Tamarind juice turns red litmus blue.

• 1) True
• 2) False

Solution

False. Tamarind juice turns blue litmus red.

Q28. What is the other name of mineral acids. Why is it advised to never taste and touch these acids?

Solution

Mineral acids are also called inorganic acids. These acids should never be tasted and touched since they are corrosive in nature and can cause skin burns.

Q29. Which of the following compound/compounds feel soapy to touch?

• 1) All of the above
• 2) Calcium hydroxide
• 3) Sodium hydroxide
• 4) Potassium hydroxide

Solution

Bases feel soapy to touch.

Q30. Which of the following is not a base?

• 1) Sodium hydrogen carbonate
• 2) Sodium hydroxide
• 3) Soap
• 4) Carbon dioxide

Solution

Sodium hydroxide, soaps and sodium hydrogen carbonate all are bases.

Q31. Which of the following substances will turn China rose indicator to green colour?

• 1) All of above
• 2) Milk of magnesia
• 3) Lime water
• 4) Soap solution

Solution

Lime water, milk of magnesia and soap solution all are bases. Bases turn China rose indicator green.

Q32. Toothpaste is slightly acidic in nature.

• 1) True
• 2) False

Solution

False. Toothpaste is slightly basic in nature.

Q33. What colour change is observed when few drops of antacid (solution) are put on turmeric paste? Explain why antacid changes colour of turmeric paste?

Solution

Antacid changes colour of turmeric paste to red. Since antacid contains magnesium hydroxide as base, it changes the colour of turmeric paste to red.

Q34. Ascorbic acid is present in ______________ fruits.

Solution

Ascorbic acid is present in sour fruits.

Q35. What are indicators?

Solution

Substances which show a change of colour with acidic or basic substance are called indicators.

Q36. Name three acids consumed by human beings through their diet and one source for each.

Solution

No. Acids consumed by human beings through their diet Source of acid 1. Tartaric acid Tamarind 2. Citric acid Orange and lemon 3. Ascorbic acid Amla

Q37. Vinegar is ________________ in nature.

Solution

Vinegar is acidic in nature.

Q38. Soaps contain _____________ in it.

Solution

Soaps contain bases in it.

Q39. Name two substances taken up by human beings in their diet which turn China rose indicator to dark pink or magenta.

Solution

Two substances taken up by human beings in their diet which turn China rose indicator to dark pink or magenta are: a. Tea b. Apples

Q40. Why are soaps slippery in nature?

Solution

Soaps contain bases like potassium hydroxide and sodium hydroxide in it. Since bases are slippery to touch, so soaps feel slippery.

Q41. What will be the effect of curd (in solution form) on blue litmus paper?

Solution

Curd will turn blue litmus to red being acidic in nature.

Q42. Which two items/substances found in kitchen will change the colour of blue litmus to red?

Solution

Substances found in kitchen that will change the colour of blue litmus to red are:(a) Vinegar(b) Tamarind (dilute solution)

Q43. Tannic acid is present in tea.

• 1) True
• 2) False

Solution

True

Q44. Sulphuric acid and nitric acid are responsible for acid rain.

• 1) True
• 2) False

Solution

True

Q45. Phenolphthalein will turn to pink colour on addition of ______________.

Solution

Phenolphthalein will turn to pink colour on addition of basic solution.

Q46. What will be the effect of basic substance on blue litmus solution?

Solution

Basic substance has no effect on blue litmus solution.

Q47. How can you correct soil of an agricultural field that has become too basic?

Solution

Basic soil can be corrected by using organic matter/manure. The decaying organic matter produces acid and this neutralises the effect of excess base in the soil.

Q48. Bases feel ________________ in touch.

Solution

Bases feel soapy in touch.