Class 10 Science: Acids, Bases and Salts important questions
Acids, Bases and Salts is a chapter of Class 10 Science for the Andhra Pradesh State Board. These 18 questions are marked Very Important, Important or Practice, and each answer has been checked by our team. Use them to revise, not as a prediction of what will come in the exam.
Practice · 1 marks
1. ________ gas is released when zinc granules react with dilute sulphuric acid.
Hydrogen. Zn + H₂SO₄ → ZnSO₄ + H₂
Important · 4 marks
2. Describe a diagram showing that an acid solution in water conducts electricity.
Fix two iron nails in a rubber cork and place it in a beaker. Connect the nails, through a switch, to a 6 V battery and a bulb. Pour dilute hydrochloric acid into the beaker so the nails dip into it and switch on. The bulb glows, showing that the acid solution conducts electricity. This is because acids form H⁺ ions in water, which carry the current.
Important · 4 marks
3. Write two important uses each of washing soda and baking soda.
Washing soda (Na₂CO₃·10H₂O): 1) Used in the glass, soap and paper industries. 2) Used for removing permanent hardness of water, and as a cleaning agent at home. Baking soda (NaHCO₃): 1) Used to make baking powder, which makes cakes and bread soft and spongy. 2) Used as an antacid to relieve acidity, and in soda-acid fire extinguishers.
Practice · 1 marks
4. Give an example of an olfactory indicator.
Onion (also vanilla essence and clove oil). Its smell changes or disappears in a basic solution.
Very Important · 8 marks
5. Write briefly about 1) Plaster of Paris 2) Bleaching powder 3) Sodium hydrogencarbonate (baking soda) 4) Sodium carbonate (washing soda)
1) Plaster of Paris, CaSO₄·½H₂O: made by heating gypsum (CaSO₄·2H₂O) at 373 K. It mixes with water and sets into hard gypsum. Used for plastering fractured bones, making toys and decorative materials, and smoothing surfaces. 2) Bleaching powder, CaOCl₂: made by passing chlorine over dry slaked lime. Used to bleach cotton, linen and wood pulp, as an oxidising agent, and to disinfect drinking water. 3) Baking soda, NaHCO₃: made from NaCl, water, CO₂ and ammonia. Used in baking powder, as an antacid and in soda-acid fire extinguishers. 4) Washing soda, Na₂CO₃·10H₂O: made by heating baking soda and recrystallising the sodium carbonate. Used in the glass, soap and paper industries, to remove permanent hardness of water, and as a cleaning agent.
Practice · 1 marks
6. Give an example of an acid.
Hydrochloric acid (HCl). Others: sulphuric acid (H₂SO₄), nitric acid (HNO₃), acetic acid (CH₃COOH).
Practice · 1 marks
7. The pH of a solution is 10. What colour does it give with methyl orange?
Yellow. pH 10 is basic, and methyl orange turns yellow in basic solutions (red in acidic ones).
Important · 4 marks
8. Write the uses of bleaching powder.
Bleaching powder (calcium oxychloride, CaOCl₂) is used: 1) for bleaching cotton and linen in the textile industry, and wood pulp in paper factories; 2) for bleaching washed clothes in laundries; 3) as an oxidising agent in many chemical industries; 4) to disinfect drinking water by killing germs.
Important · 2 marks
9. What happens if curd or other sour substances are kept in brass or copper vessels?
Curd and sour foods contain acids. The acids react with copper and brass (an alloy of copper and zinc) to form harmful, poisonous compounds that spoil the food and can make people ill. So sour foods should not be kept in such vessels.
Practice · 1 marks
10. A student finds that the pH of a solution is 3. Suggest one way to neutralise it.
pH 3 is acidic. Add a base slowly, such as dilute sodium hydroxide solution or a weak base like baking soda (sodium hydrogencarbonate), checking with pH paper until the pH reaches 7.
Practice · 1 marks
11. While preparing dilute sulphuric acid, which action should the students perform? A) Add water slowly to concentrated acid. B) Add concentrated acid slowly to water. C) Mix acid and water at the same time. D) Heat the acid before dilution.
B) Add the concentrated acid slowly to water, stirring constantly. Mixing gives out a lot of heat; adding water to acid can make the mixture boil and splash acid out.
Important · 4 marks
12. Describe a neat diagram of the chlor-alkali process.
A container holds brine (concentrated sodium chloride solution) with two electrodes connected to a battery. At the anode (+), chlorine gas is released; at the cathode (−), hydrogen gas is released; sodium hydroxide solution forms near the cathode. 2NaCl(aq) + 2H₂O(l) → 2NaOH(aq) + Cl₂(g) + H₂(g) The name 'chlor-alkali' comes from the products: chlorine and an alkali (sodium hydroxide).
Important · 4 marks
13. Rohan says washing soda is used to bake a cake and baking soda to soften hard water. His sister Sowmya disagrees. 1) Who is correct? 2) Write the formula of baking soda. 3) Write two uses of the substance used to bake a cake.
1) Sowmya is correct. Baking soda is used in baking, and washing soda is used to soften hard water. 2) Baking soda is sodium hydrogencarbonate, NaHCO₃. 3) Uses of baking soda: as baking powder (with a mild acid like tartaric acid) to make cakes and bread soft and spongy; as an antacid to relieve acidity; in soda-acid fire extinguishers.
Practice · 1 marks
14. A student wants to test whether a solution is acidic. Suggest one safe and simple test.
Dip blue litmus paper in it: an acid turns blue litmus red. (Or use pH paper: a pH below 7 means acidic.)
Practice · 1 marks
15. During a Swachh Seva camp, students must make the school drinking water safe. Which action shows care for the health of others? A) Mixing bleaching powder to disinfect the drinking water. B) Adding washing soda to the drinking water. C) Storing bleaching powder packets near the tank. D) Decorating the water tank with posters.
A) Bleaching powder (CaOCl₂) is used to disinfect drinking water by killing germs.
Important · 4 marks
16. Describe a neat diagram of the reaction of zinc granules with dilute sulphuric acid.
Set-up: zinc granules and dilute sulphuric acid in a test tube, closed with a cork. A delivery tube leads the gas into a soap solution, forming bubbles. A burning candle brought near a gas-filled bubble makes a 'pop' sound. The gas is hydrogen: Zn(s) + H₂SO₄(aq) → ZnSO₄(aq) + H₂(g). This shows that acids react with metals to give a salt and hydrogen gas.
Important · 4 marks
17. In a school lab, Group A says to dilute a concentrated acid by adding water to the acid. Group B says to add the acid to water. Whose argument is correct, and why?
Group B is correct. Diluting a concentrated acid is highly exothermic (it gives out a lot of heat). Adding water to the acid can make the mixture boil suddenly and splash acid out, causing burns, and the glass may crack. Adding the acid slowly to water, with constant stirring, spreads the heat safely.
Important · 4 marks
18. Arun says hydrochloric acid turns blue litmus red. Is this correct under all conditions? Justify.
Only when water is present. HCl shows acidic behaviour by forming H⁺ (H₃O⁺) ions in water. Dry HCl gas does not change the colour of dry blue litmus paper, but it turns moist blue litmus red.
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