The soil in a field is highly acidic. Name two materials which can be added to this soil to reduce its acidity. Give the reason for your choice.

28 Under what soil conditions do you think a farmer would treat the soil of his fields with quicklime (calcium oxide), or slaked lime (calcium hydroxide) or chalk (calcium carbonate)? 29 Which acid is produced in our stomach? What happens if there is an excess of acid in the stomach? How can its effect be cured? 31 What is meant by strong bases and weak bases? Classify the following into strong bases and weak bases:

NH₄OH, Ca(OH)₂, NaOH, KOH, Mg(OH)₂

32 What ions are present in the solutions of following substances? (write the symbols only)

(i) Hydrochloric acid (ii) Nitric acid (iii) Sulphuric acid (iv) Sodium hydroxide (v) Potassium hydroxide (vi) Magnesium hydroxide