Acid Base and Salt

NCERT Exercise Solution - Part I

Write word equations and then balanced equations for the reaction taking place when

  1. Dilute sulphuric acid reacts with zinc granules.

    Answer: Sulphuric acid + Zinc → Zinc sulphate + Hydrogen

    Zn + H2SO4 ⇨ ZnSO4 + H2
  2. Dilute hydrochloric acid reacts with magnesium ribbon.

    Answer: Hydrochloric acid + Magnesium → Magnesium chloride + Hydrogen

    Mg + 2HCl ⇨ MgCl2 + H2
  3. Dilute sulphuric acid reacts with aluminium powder.

    Answer: Suphuric acid + Aluminium → Aluminium sulphate + Hydrogen

    2Al + 3H2SO4 ⇨ Al2(SO4 )3 + 3H2
  4. Dilute hydrochloric acid reacts with iron filings.

    Answer: Sulphuric acid + Iron → Ferric chloride + Hydrogen

    2Fe + 6HCl ⇨ 2FeCl3 + 3H2

A solution turns red litmus blue, its pH is likely to be

  1. 1
  2. 4
  3. 5
  4. 10

Answer: (d) 10

A solution reacts with crushed egg-shells to give a gas that turns lime-water milky. The solution contains

  1. NaCl
  2. HCl
  3. LiCl
  4. KCl

Answer: (b) HCl

10 mL of a solution of NaOH is found to be completely neutralised by 8 mL of a given solution of HCl. If we take 20 mL of the same solution of NaOH, the amount HCl solution (the same solution as before) required to neutralise it will be

  1. 4 mL
  2. 8 mL
  3. 12 mL
  4. 16 mL

Answer: (d) 16 mL

Which one of the following types of medicines is used for treating indigestion?

  1. Antibiotic
  2. Analgesic
  3. Antacid
  4. Antiseptic

Answer: (c) Antacid

Compounds such as alcohols and glucose also contain hydrogen but are not categorised as acids. Describe an Activity to prove it.

Answer: Following activity can be done for this:

It is observed that bulb does not glow using glucose or alcohol solution. While if a solution of acid is used instead of glucose or alcohol solution, bulb glows.

Bulb glows when the solution of hydrochloric acid is used, because it dissociates into hydronium ion in aqueous solution. But glucose and alcohol do not dissociate hydronium ion in the water. Hence solution of glucose and alcohol do not conduct electricity.

Why does distilled water not conduct electricity, whereas rain water does?

Answer: Rain water contains acids and many other substances as impurities, which produce hydronium ion, while distilled water does not contain any ionic substance that can dissociate into hydronium ion. That’s why rain water conducts electricity and distilled water does not.

Why do acids not show acidic behaviour in the absence of water?

Answer: Hydronium ions are responsible for behavior as acid. Acids do not dissociate into hydronium ions in the absence of water, hence they do not show acidic behavior in absence of water.

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