Acids, bases and salts Worksheet-11

Acids, bases and salt Worksheet-11

True/False:

1. Phenophthalein turns pink when an acid is added to it.

2. Saliva(after meals) gives red colour with Methyl orange.

3. Formic acid is a strong acid.

4. Optimum pH for activity of pepsin is 2-2.5.

5. The tooth enamel is made of Calcium Phosphate which gets damaged when pH of the mouth is less than 5·5.

6. When a wasp strings, rubbing the affected skin with washing soda gives relief.

7. Common salt is obtained from the sea water by its electrolysis.

8. The colour of phenolphthalein in rain water is red.

9. Zinc carbonate (ZnCO₃) is the salt of carbonic acid. and Zinc oxide.

10. Ammonium sulphate (NH₄)SO₄ is the salt of weak acid & strong base.

11. pH of sodium sulphate solution is less than 7.

12. pH of aqueous solution of sodium carbonate is more than 7.

13. During electrolysis of brine (aq. sodium-chloride) sodium hydroxide is formed near anode.

14. Washing soda attacks dirt and Grease forming water insoluble substance which easily gets rinsed off.

15. Calcium carbonate is soluble in water.

16. Aluminium sulphate is the salt of aluminium oxide and sulphuric acid.

17. The optimum pH for the activity of trypsin is 9-12.

18. The optimum pH for the activity of chymotrypsin is 4-5.

19. The optimum pH for activity of amylase is 8-9.

20. Magnesium chloride is the salt of weak acid and strong base.

Answer key:

1. False

It remains colourless.

2. True

3. False

It is an organic acid and is a weak acid.

4. True

5. True

6. False

When a wasp stings it injects alkaline liquid so rubbing the skin with vinegar will give relief.

7. False

It is obtained from sea water by evaporation.

8. False

Rain water is acidic and phenolphthalein is colourless in acidic medium

9. True

10. False

It is the salt of weak base NH₄OH and strong acid H₂SO₄.

11. False

Sodium sulphate is the salt of strong acid (H₂SO₄) and strong base NaOH so its solution will be neutral.

12. True

13. False

NaOH is formed near the cathode.

14. False

Washing soda forms water soluble products with dirt and grease.

15. False

It is insoluble in water.

16. False

It is the salt of aluminium hydroxide and sulphuric acid.

17. True

18. False

Chymotrypsin is present intestine and its optimum ph is 9-11.

19. False

Its optimum activity is in neutral medium.

20. False

It is the salt of strong acid and a strong base.