ACIDS, BASES AND SALTS – 3 Mark Questions

Q1.  How the following substances will dissociate to produce ions in their solutions?

(i)    Hydrochloric acid

(ii)   Nitric Acid

(iii)  Sulphuric acid

(iv)  Sodium hydroxide

(v)   Potassium hydroxide

(vi)  Magnesium hydroxide             

Q2.  What is tooth enamel chemically? State the condition when it starts corroding. What happens when food particles left in the mouth after eating degrades? Why do doctors suggest use of tooth powder/ toothpaste to prevent tooth decay?

Q3. State  reason for the following:

(i)   Dry HCl gas does not change the colour of the dry blue litmus paper.

(ii) Alcohol and glucose also contain hydrogen but do not conduct electricity.

(iii)   Concentration of H3O+ ions is affected when a solution of an acid is diluted.

Q4.Explain the action of dilute hydrochloric acid on the following with chemical equation:

(i) Magnesium ribbon

(ii) Sodium Hydroxide

(iii) Crushed egg shells.

Q5.  (a) What is the action of litmus on:

                              (i) Dry ammonia gas

                              (ii) Solution of ammonia gas in water

  (b) State the observation you would make on adding sodium hydroxide to aqueous solution of:

                              (i)  Ferrous Sulphate

                              (ii) Aluminium chloride

               Give balanced chemical equation.

Q6. A few crystals of copper sulphate are heated in dry boiling tube:

(i) What is the colour before and after heating?

(ii) What is the reason for the colour change?

(iii) Can its original colour be restored? How?

Q7. A sanitary worker uses a white chemical having strong smell of chlorine gas to disinfect the water tank.

(i) Identify the chemical compound, write its chemical formula.

(ii) Give chemical equation for its preparation.

(iii) Write its two uses other than disinfection.

Q8. “Sodium hydrogen carbonate is a basic salt. “Justify the statement. How is it converted into washing soda? Explain. 

Q9. To an aqueous solution of sodium hydroxide, a few drops of phenolphthalein were added. What do you observe?  To this solution small amount of dil. HCI was added. What do you observe now? Explain your answer.

Q10.  Answer the following.

(a) Why is sodium hydrogen carbonate an essential ingredient in ant-acids?

(b) What happens, when crystals of washing soda are left open in dry air?

(c) Why does milkman add a small amount of baking soda to fresh milk?

Q11. (a) Why curd or sour substances should not be kept in brass and copper vessels?

            (b) Aqueous solution of HI shows acidic character, whereas aqueous solution of glucose does not. Why?

            (c) What will you observe when a small amount of copper oxide is added in a beaker containing dilute Hydrochloric Acid?

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