Important Questions From Acid Base and Salt

Q. When a piece of limestone reacts with dilute HCl, a gas X is produced. When gas X is passed through lime water then a white precipitate Y is formed. On passing excess of gas X, the white precipitate dissolves forming a soluble compound Z.

    • What are X, Y and Z ?
    • Write equations for the reactions which take place :
    • when limestone reacts with dilute HCl
    •  when gas X reacts with lime water to form white precipitate Y
    •  when excess of gas X dissolves white precipitate Y to form a soluble compound


  • X is carbon dioxide; Y is calcium carbonate; Z is calcium hydrogen carbonate

    Q. If someone is suffering from the problem of acidity after overeating, which of the following would you suggest as remedy ? Lemon juice, Vinegar, Baking soda solution Give reason for your choice.

  • ANSWER– In such condition we use Baking Soda because it is a basic salt.
  • This basic salt will neutralize the excess of acidity and provide relief to the person.

Q.What would you expect the pH of pure water to be ?
What colour would the universal indicator show in an aqueous solution of sugar ? Why
A sample of rain water turned universal indicator paper yellow. What would you expect its pH to be ? Is it a strong or a weak acid ?

  • ANSWER– The pH of pure water is 7.
  • the sugar solution is neutral in nature hence universal indicator show green colour.
  • the sample of rain water turned universal indicator paper yellow, this shows that is a weak acid.

Q. What is a salt ? Give the names and formulae of any two salts. Also name the acids and bases from which these salts may be obtained.

  • ANSWER– salt is a chemical compound which is formed by the reaction of an
    acid with a base.
  • sodium chloride salt ( NaCl) it is prepared by reaction between sodium hydroxide base and hydrochloric acid .
  • potassium chloride (KCl) it is prepared by reaction between potassium hydroxide base and hydrochloric acid .

 Q. What is meant by ‘a family of salts’ ? Explain with examples.

  • ANSWER – when salts are prepared by reaction between same acids or same bases,
    they are classified as a family.
  • example- sodium chloride and potassium chloride are salts that belong to the
    chloride family because of the chloride radicals in them.

Q. What is meant by ‘hydrated’ and ‘anhydrous’ salts ? Explain with examples.

  • ANSWER – A chemical compound which have one or more chemically bonded water molecule in the structure lattice of compound are known as hydrated salts
    Example: Copper sulphate pentahydrate (CuSO4.5H2O)
  • Anhydrous salt: A chemical compound in which all water molecules are removed from main strucutre lattice of compound is called Anhydrous salt.
  • example : copper sulphate pentahydrate convert into copper sulphate on heating

Q. Write the names, formulae and colours of any two hydrated salts?

  • ANSWER -copper sulfate pentahydrate – CuSO4.5H2O – blue in colour
    Cobalt chloride – CoCl. 6H2O – Pink

Q. What will be the colour of litmus in an aqueous solution of ammonium chloride salt ?

  • ANSWER – aqueous solution of ammonium chloride salt is acidic in nature.
  • red litmus paper show no colour change and it turn a blue litmus paper to red
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