General Science Solutions Solutions for Class 8 Science Chapter 12 Introduction To Acid & Base are provided here with simple step-by-step explanations. These solutions for Introduction To Acid & Base are extremely popular among Class 8 students for Science Introduction To Acid & Base Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the General Science Solutions Book of Class 8 Science Chapter 12 are provided here for you for free. You will also love the ad-free experience on Meritnation’s General Science Solutions Solutions. All General Science Solutions Solutions for class Class 8 Science are prepared by experts and are 100% accurate.

Page No 88:

Question 1:

Identify the following solutions, whether they are acid or alkali.
 

Solution Change in Indicator Acid/Alkali
  Litmus Phenolphthalein Methyl orange  
1. ... No change ...  
2. ... ... Orange colur turns red  
3. Red litmus turns blue ... ...  

Answer:

Identify the following solutions, whether they are acid or alkali.
 

Solution Change in Indicator Acid/Alkali
  Litmus Phenolphthalein Methyl orange  
1. Blue litmus turns red No change Orange colour turns red Acid
2. Blue litmus turns red No change Orange colour turns red Acid
3. Red litmus turns blue Colourless to pink Orange colour turns yellow Alkali

Page No 88:

Question 2:

Write chemical names from given formulae.
H2SO4,   Ca(OH)2,    HCl,  NaOH,  KOH, NH4OH

Answer:


H2SO4 = Hydrogen sulphate
Ca(OH)2 = Calcium hydroxide
HCl = Hydrogen chloride
NaOH = Sodium hydroxide
KOH = Potassium hydroxide
NH4OH = Ammonium hydroxide

Page No 88:

Question 3:

Sulphuric acid has highest importance in chemical industry. Why?

Answer:


Sulphuric acid is a chemical of major industrial importance. It is difficult to imagine life without it. Since, it is used in the manufacturing of a vast array of materials. Sulphuric acid can either be Concentrated or Diluted.

  • Concentrated sulphuric acid is a colourless, viscous liquid that absorbs water vapour from the air and becomes a solution. It is hygroscopic. It is a good dehydrating agent and shows some oxidising ability.
  • Dilute sulphuric acid behaves like a typical acid, reacting with metals to give hydrogen and a metal sulphate (i.e. it is corrosive), with metal carbonates to give carbon dioxide, water, and a metal sulphate and with bases give a metal sulphate and water.
Sulphuric acid has highest importance in chemical industry as :
1.Sulphuric acid is used in manufacturing fertilizers such as super phosphate, ammonium sulphate etc.
2.Sulphuric acid is used in the manufacture of dyes.
3.Nitric acid is used in the manufacture of paints.
4.Sulphuric acid is used in the manufacture of drugs.
5.Sulphuric acid is used in the manufacture of explosives.
6.Sulphuric acid is used in batteries, which is used in cars.
7.Tannic acid is used in the manufacture of ink and leather.
8.Hydrochloric acid is used to make aqua regia, which is used to dissolve noble metals such as gold and platinum.
9.Sulphuric acid is used in the manufacture of jet fuel, kerosene and leather.

Page No 88:

Question 4:

Give answers
a. Which acid is used for getting chloride salt ?
b. By squizzing lemon on a piece of rock the gas liberated turned lime water milky. which compound is present in the rock ?
c. The label on the bottle of chemical is spoiled. How will you find whether the chemical is acidic or not ?  

Answer:


a.Acid used for getting chloride salt is HCl because this acid provides chloride ion to form chloride salt.
For example :
HCl + NaOH NaCl + H2OHCl + Mg(OH)2  MgCl2 + H2O

b.Compound presents in the rock is either a compound of carbonate or bicarbonate because acids react with carbonate or bicarbonate and liberate CO2. This carbon dioxide turns lime water milky.

c.The chemical is acidic or not checked by two ways :
1.By use of litmus paper : If the given solution is acidic, it turns blue litmus  to red litmus.
                                          If the given solution is basic, it turns red litmus  to blue litmus.
                                          If the given solution is neutral, there is no effect on litmus paper.
2.By use of indicators : If the given solution is acidic, it turns methyl orange to red.
                                      If the given solution is basic, it turns methyl orange to yellow
                                      If the given solution is neutral, there is no effect on methyl orange indicator.

Page No 88:

Question 5:

Answer the following questions.
a.Explain the difference between acid and alkali.
b.Why indicator does not get affected by salt?
c.Which substances are produced by neutralization process?
d.Which are the industrial uses of adids ?

Answer:

 a.Difference between acid and alkali :


Parameter
 
 Acid  Alkali
Nature of oxides
metal oxides are generally alkaline in nature

non-metal oxides are basic in nature
Arrhenius Definition substance which when dissolved in water gives hydrogen ion substance which when dissolved in water can accept hydrogen ions
Bronstead Lowry Definition substance which donates a proton substance which accepts a proton
Strength depends on the concentration of the hydronium ions depends on the concentration of the hydroxide ions
 Characteristics (Physical)
  • depend upon the temperature as it can be solid, liquid or in the form of gas
  • have a sour taste
  • solid in nature except ammonia which is gaseous
  • have a bitter taste
  • slippery in touch
Dissociation would release hydrogen ions (H+) when mixed with water would release hydroxide ions(OH-) when mixed with water
pH value less than 7.0 greater than 7.0
Litmus paper blue litmus paper turns red red litmus paper turns blue
Chemical Formula has a chemical formula with H at the beginning of it. For example, HCl (Hydrochloric Acid). There is one exception to this rule, CH3COOH = Acetic Acid (vinegar) has a chemical formula with OH at the end of it. For example, NaOH (Sodium Hydroxide)

b.Indicators do not get affected by salts because salts are neutral in nature. Indicators work only with acidic and basic substances.
For example:
Indicator Acidic substance Basic substance
Phenophthalein colourless turns pink
Methyl orange methyl orange turns red methyl orange turns yellow

c.Neutralization reaction: A neutralization reaction is a reaction when an acid and a base reacts to form water and a salt. It involves the combination of H+ ions and OH- ions to generate water.
The neutralization of a strong acid and strong base has a pH equal to 7. That means salts are neutral in nature.
The neutralization of a strong acid and weak base will have a pH of less than 7. That means salts are acidic in nature.
The neutralization of a strong base neutralizes a weak acid will be greater than 7. That means salts are basic in nature.
null
d. Industrial uses of acid are :
1.Sulphuric acid is used in manufacturing fertilizers such as super phosphate, ammonium sulphate etc.
2.Sulphuric acid is used in the manufacture of dyes.
3.Nitric acid is used in the manufacture of paints.
4.Sulphuric acid is used in the manufacture of drugs.
5.Sulphuric acid is used in the manufacture of explosives.
6.Sulphuric acid is used in batteries, which is used in cars etc.
7.Tannic acid is used in the manufacture of ink and leather.
8.Hydrochloric acid is used for making aqua regia, which is used to dissolve noble metals such as gold and platinum.
9.Sulphuric acid is used in the manufacture of jet fuel, kerosene and leather.

Page No 88:

Question 6:

Select proper word given in bracket and fill in the blanks.
a.Main constituent of acid is......................
b.Main constituent of alkali is...................
c.Tartaric acid is a................ acid.

Answer:


a.Main constituent of acid is H+ ion.
b.Main constituent of alkali is OH- ion.
c.Tartaric acid is a weak acid.

Page No 88:

Question 7:

Match the pairs. 

  Group A  Group B
1. Tamarind  a. Acetic acid
2. Curd  b. Citric acid
3. Lemon  c. Tartaric acid
4.Vinegar d. Lactic acid

Answer:

 

  Group A  Group B
1. Tamarind  a. Tartaric acid
2. Curd  b. Lactic acid
3. Lemon  c. Citric acid
4. Vinegar  d. Acetic acid

Page No 88:

Question 8:

State true of false
a. Oxides of metals are alkaline in nature.
b.Salt is acidic
c.Metal corrodes due to salts
d.Salts are neutral.

Answer:


a. Oxides of metals are alkaline in nature = True
b. Salt is acidic = False
c. Metal corrodes due to salts = True
d. Salts are neutral = True

Page No 88:

Question 9:

Classify following substances into acidicm basic and neutral group-
HCl,   NaCl,  MgO,  KCl,  H2SO4,  HNO3,  H2O,  Na2CO3

Answer:


HCl = Acidic
NaCl = Neutral
MgO = Basic
KCl = Neutral
H2SO4 = Acidic
HNO3 = Acidic
H2O = Neutral
Na2CO3 = Basic



View NCERT Solutions for all chapters of Class 8