Samacheer Kalvi Class 8 Science Unit 14 Acids and Bases Solutions
Welcome to NCTB Solutions. Here with this post we are going to help 8th class students by providing Solutions for Samacheer Kalvi Class 8 Science Unit 14 Acids and Bases. Here students can easily find all the solved solution for Acids and Bases Exercise questions. Also here our Expert Science Teacher’s solved all the questions with easily understandable language with proper guidance so that all the students can understand easily. Here on this post students will get Unit 14 Acids and Bases exercise solutions. Here all the solutions are based on Tamil Nadu State Board latest syllabus.
Unit 14 Acids and Bases Exercise Questions Solutions :
(I) Choose the best answer
(1) Acids are ___ in taste
(a) Sour
(b) Sweet
(c) Bitter
(d) Salty
Answer :
Correct Option → (a)
Acids are Sour in taste.
(2) Aqueous solutions of ___ conduct electricity
(a) Acid
(b) Base
(c) Salt
(d) All of these
Answer :
Correct Option → (d)
Aqueous solutions of Acid, Base, and Salt conduct electricity.
(3) In acidic solutions blue litmus changes into __ color
(a) Blue
(b) Green
(c) Red
(d) White
Answer :
Correct Option → (c)
In acidic solutions blue litmus changes into Red color.
(4) Base is a substance that gives ___ on dissolving in water
(a) OH-
(b) H+
(c) OH
(d) H
Answer :
Correct Option → (a)
Base is a substance that gives OH- on dissolving in water.
(5) Sodium hydroxide is a ___
(a) Acid
(b) Base
(c) Oxide
(d) Alkali
Answer :
Correct Option → (b)
Sodium hydroxide is a Base.
(6) Red ant sting contains ___
(a) Acetic acid
(b) Sulphuric acid
(c) Oxalic acid
(d) Formic acid
Answer :
Correct Option → (d)
Red ant sting contains Formic acid.
(7) Magnesium hydroxides are used for treating __
(a) acidity
(b) head pain
(c) teeth decay
(d) None of these
Answer :
Correct Option → (a)
Magnesium hydroxides are used for treating acidity.
(8) Acid mixed with base forms ___
(a) Salt and water
(b) Salt
(c) Water
(d) No reaction
Answer :
Correct Option → (a)
Acid mixed with base forms Salt and water.
(9) We brush our teeth with tooth paste because it is ___ in nature
(a) Basic
(b) Acidic
(c) Both a and b
(d) None of these
Answer :
Correct Option → (a)
We brush our teeth with tooth paste because it is Basic in nature.
(10) In basic solution turmeric indicator paper changes from yellow to ___
(a) Blue
(b) Green
(c) Yellow
(d) Red
Answer :
Correct Option → (d)
In basic solution turmeric indicator paper changes from yellow to Red.
(II) Fill in the blanks
(1) Benzoic acids are used for ___
(2) The word sour refers to ___ in Latin.
(3) Bases are ___ in taste.
(4) Chemical formula of calcium oxide is ___
(5) Wasp sting contains ___
(6) Turmeric is used as a ___
(7) In acidic solution the colour of the hibiscus indicator paper will change to ___
Answer :
(1) → Preserved food material
(2) → Acidus
(3) → Bitter
(4) → CaO
(5) → Alkaline substance
(6) → Natural indicator
(7) → Deep pink or deep red
(III) State true or false. If false, correct the statement
(1) Most of the acids are not soluble in water.
(2) Acids are bitter in taste.
(3) Bases are soapy to touch when they are dry.
(4) Acids are corrosive in nature.
(5) All bases are alkalis.
(6) Hibiscus flower is an example for natural indicator.
Answer :
(1) → True
(2) → False, because acid are sour in taste.
(3) → False, because bases are soapy to touch only in aqueous solution.
(4) → True
(5) → False, because not all bases are alkali but all alkalis are bases
(6) → True
(IV) Answer briefly
(1) Acid – Define.
Answer :
The compounds have sour taste are called Acids. Or acids are the chemical a substance which release hydrogen ions when dissolved water.
(2) Write any four physical properties of acids.
Answer :
Physical properties of acids are :-
- Acids are sour in taste
- Acids are corrosive in nature.
- Acids are clourless
- Acids solution conducts electricity
(3) What are the similarities between acids and bases?
Answer :
Similar properties of acids and bases are :-
- They both are corrosive in nature.
- They both undergoes ionization in aqueous solution.
- They conduct electricity in aqueous solution.
- They undergo neutralization reaction.
(4) State the difference between acids and bases.
Answer :
Acids :
- They produce H+ ions in water.
- They are sour in taste.
- Few acids are in solid state
- Acids turn blue litmus paper red
Bases :
- They produces OH- ions in water.
- They are bitter in taste.
- Most of the bases are in solid state
- Bases turns red litmus paper blue
(5) What is an indicator?
Answer :
Indicator is the chemical substance which indicates the acid or basic nature of a solution by suitable color change.
(6) What is a neutralization reaction?
Answer :
Neutralization reaction is the chemical reactions in which an acid and a base react with each other to form salt and water.
Acid + base → Salt + Water.
(7) Write any four physical properties of base.
Answer :
Physical properties of base are :-
- Bases gives soapy touch only in aqueous medium not in dry medium or nature.
- Bases are bitter in taste
- Bases are corrosive in nature.
- Bases generally colorless.
- Bases exist in solid state but some are in liquid state also for eg- ammonium hydroxide.
(V) Answer in detail
(1) What are the uses of acids?
Answer :
Acids are used in industries to produce battery, chloride salts, dyes, explosives, paints, sterilize water and to make white paper from wood pulp.
(2) What are the uses of bases?
Answer :
The uses of bases are :-
- Potassium hydroxide is used to make bathing soaps.
- Sodium hydroxide is used to make washing soaps.
- Sodium hydroxide is also used to make in paper industries,textile industries and in the preparation of medicines.
- Calcium hydroxide is used for white washing.
- Aluminum hydroxide and magnesium hydroxides are used in antacids to cure acidity problems.
- Ammonium hydroxide is used to manufacturing fertilizers, nylon ,plastics and rubber etc.
(4) How will you prepare natural indicator from turmeric powder.
Answer :
Natural indicators are the chemical substances which are obtained from the natural resources. Turmeric is also natural indicator. By adding small amount of water into turmeric powder a paste is prepared. This paste is applied on a blotting paper or filter paper and dired. These strips are used as indicators to find the nature of the solution. From this we can determine in acidic solution turmeric indicator paper has no change in colour and in basic solution the colour changes from yellow to red. This is the natural indicator of turmeric powder can indicate acid and base.
(VI) Higher Order Thinking Questions.
(1) Vinu and Priyan take their lunch at school. Vinu eats lemon rice and Priyan eats curd rice. Both lemon rice and curd rice are sour in taste. What is the reason?
Answer :
Both lemon ice and curd ice are sour in taste because lemon and curd contain acid in it and as we known acid are sour in taste, lemon contain citric acid and curd contain lactic acid therefore they are sour in taste.
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