5

Q1. Which type of reaction is curing of indigestion?

Solution

Curing of indigestion is an example of a neutralisation reaction.

Q2. What is an antacid? How does an antacid work?

Solution

Antacids are a group of mild bases which have no toxic effects on body and are used to cure indigestion. Being basic in nature, antacids react with excess acid in the stomach and neutralise it.

Q3. What will be the colour change on addition of vinegar to blue litmus paper?

Solution

Vinegar contains acetic acid and turns blue litmus to red.

Q4. 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.

Q5. 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.

Q6. (a) What is an indicator? (b) Three liquids are given to you. One is sulphuric acid, another is sodium hydroxide and the third is a salt solution. How will you identify them? You have only turmeric paper indicator.

Solution

(a) An indicator is a dye that changes color when it is put into an acid or a base. (b) Put one drop of each liquid on turmeric paper, turn by turn. (i) The liquid which turns the yellow turmeric paper red will be sodium hydroxide (base). The red turmeric paper formed here can now be used to test sulphuric acid. (ii) Put one drop each of the remaining two liquids on red turmeric paper. The liquid which makes the red turmeric paper yellow again will be sulphuric acid (This is because sulphuric acid cancels the effect of sodium hydroxide base on turmeric paper). (iii) The liquid which has no effect on the red turned turmeric paper will be salt solution (because it is neutral).

Q7. Neutralisation reactions play a very important role in soil treatment. Elaborate. 

Solution

Neutralisation reactions play a very important role in soil treatment. The soil may be acidic or basic naturally. The plants do not grow well if the soil at a place is too acidic or too basic. The excessive use of chemical fertilisers in the fields also makes the soil too acidic. When the soil is too acidic, it is treated with bases such as quicklime (calcium oxide) or slaked lime (calcium hydroxide). The bases such as quicklime (or slaked lime) neutralise the excess acid present in the soil and reduce its acidic nature. Thus, a farmer should add quicklime (or slaked lime) in the fields if the soil is too acidic. Sometimes, however, the soil is too basic. If the soil is too basic, then decaying organic matter (called manure or compost) is added to it. The decaying organic matter releases acids which neutralise the excess bases present in the soil and reduce its basic nature. Thus, a farmer should add decaying organic matter (manure or compost) in his fields if the soil is too basic.

Q8. What will be the effect of basic substance on blue litmus solution?

Solution

Basic substance has no effect on blue litmus solution.

Q9. Which indicator will turn blue on adding lime water?

Solution

Red litmus paper will turn blue on adding lime water because lime water is basic in nature.

Q10. Is litmus a natural indicator or synthetic? What color change does it undergo in distilled water?

Solution

Litmus is a natural indicator. In distilled water, its color is purple.

Q11. 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.

Q12. Give two damages caused by acid rain.

Solution

Damages caused by acid rain: 1. It makes the water of lakes, rivers and ponds too acidic due to which aquatic animals get killed. 2. It damages the metal structures like bridges, buildings etc.

Q13. Write name of the base present in milk of magnesia.

Solution

Magnesium hydroxide is the base present in milk of magnesia.

Q14. Name the indicator obtained from lichens.

Solution

Litmus indicator is obtained from lichens.

Q15. Give one use of magnesium hydroxide.

Solution

Magnesium hydroxide is used in making antacids.

Q16. Which type of substances-acidic, basic or neutral can turn the China rose indicator to green?

Solution

Basic substances can turn the China rose indicator to green colour.

Q17. Name the two indicators used for testing acids.

Solution

Indicators used for testing acids are: (a) Blue litmus paper (b)China rose solution

Q18. 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)

Q19. 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.

Q20. What are alkalis? Give one example.

Solution

The bases which are soluble in water are called alkalis. Ex: Sodium hydroxide.

Q21. (a) What is a salt? (b) What are the different types of salts? Give one example of each.

Solution

(a) A salt is a substance formed by the reaction of an acid with a base. (b) Salts can be of three types:  (i) Neutral salts- Those salts which form a neutral solution on dissolving in water are called neutral salts. The salts formed by the neutralisation of a strong acid by a strong base are neutral salts. Example: Sodium chloride (NaCl).  (ii) Acidic salts- Those salts which form an acidic solution on dissolving in water are called acidic salts. The salts formed by the neutralisation of a strong acid with a weak base are acidic salts. Examples: Ammonium chloride (NH₄Cl).  (iii) Basic salts- Those salts which form basic solutions on dissolving in water are called basic salts. The salts formed by the neutralisation of weak acids with strong bases are basic salts. Example: Sodium carbonate (Na₂CO₃).

Q22. Why do turmeric stain becomes red after washing the clothes with soap solution?

Solution

Soap solution contains sodium hydroxide or potassium hydroxide. Bases turn turmeric stain to red.

Q23. 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

Q24. Classify the following as strong and weak acids: Sulphuric acid, acetic acid, carbonic acid, nitric acid.

Solution

Strong acids: Sulphuric acid and nitric acid Weak acids: Acetic acid and carbonic acid

Q25. What are the different types of salts?

Solution

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

Q26. 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.

Q27. 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.

Q28. Name three indicators obtained from nature.

Solution

Indicators obtained from nature are: a. Litmus b. Turmeric c. China rose

Q29. Name three fruits which will turn blue litmus to red.

Solution

Three fruits that will turn blue litmus to red are: a. Mango b. Grapes c. Orange

Q30. (a) Which acid is produced in our stomach? Write its chemical formula. (b) What is the use of this acid? (c) What happens if there is an excess of acid in the stomach? (d) How can its effect be cured?

Solution

(a) Our stomach produces hydrochloric acid. Its chemical formula is HCl. (b) This hydrochloric acid helps in digesting our food without harming the stomach. (c) Excess of acid in the stomach causes indigestion which produces pain and irritation. (d) In order to cure indigestion and get rid of pain, we can take bases called antacids. These are a group of mild bases which have no toxic effects on the body. Being basic in nature, they react with excess acid in the stomach and neutralise it.

Q31. What is the origin of word acid?

Solution

The word acid comes from the Latin word 'acere' which means sour.

Q32. Name three substances which do not show colour change with China rose indicator.

Solution

Substances which do not show colour change with China rose indicator are: a. Water b. Sugar solution c. Salt solution

Q33. Name three fruits having tartaric acid in them.

Solution

Following fruits contain tartaric acid:- (i) Unripe mango(ii) Grapes(iii) Tamarind

Q34. 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.

Q35. 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

Q36. How will you show the presence of acid in orange juice?

Solution

We can perform the litmus test to show the presence of acid in orange juice as follows: (i) Take some orange juice in a test-tube and add a little water to it. (ii) Put a drop of the orange juice solution on a strip of red litmus paper with the help of a dropper. We will find that there is no change in the colour of red litmus paper. This means that orange juice is not basic in nature (because only basic substances or bases turn red litmus to blue). (iii) Now put a drop of orange juice solution on a strip of blue litmus paper. The blue litmus paper turns red. This shows that orange juice is acidic in nature (or orange juice contains an acid). This is because only acidic substances or acids turn blue litmus to red.

Q37. Name the base present in milk of magnesia. What is it used for?

Solution

Magnesium hydroxide is the base present in milk of magnesia. It is used to neutralise the excess acid present in stomach and is hence used as an antacid.

Q38. Define organic acids. Give one example.

Solution

Organic acids are the naturally occuring acids found in fruits and vegetables. For ex: Lactic acid.

Q39. Will common salt solution show any change on turmeric powder?

Solution

No, common salt solution will not show any change on turmeric paper since it is a neutral substance.

Q40. Name the acid present in spinach.

Solution

Oxalic acid is present in spinach.

Take Another Test