Acids Bases and Salts Chapter Wise Important Questions Class 10 Science

 THE EDUTECH

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Short Answer Type Questionss[ll] [3 Marks] –Year 2015

4. (a) Define olfactory indicators. Name two substances which can be used as an olfactory indicator.
(b) Choose powerful acids from the following:
CH₃COOH, H₂SO₄, H₂CO₃, HNO₃₃
Answer.
(a) Those substances whose smell (odour) varies in acidic or basic solution are called olfactory indicators, e.g. onions and vanilla.
(b) H₂SO₄ and HNO₃    are strong acids.

5.A white coloureds powder is used by doctors for supporting fractured bones.
(a) Write the chemicall name and formula of the powder.
(b) When this white powder is mixed with water a hard solid mass is received. Write balanced chemical equations for the change.
Answer-.

6.Explain one reaction of dilute hydrochloric acid on the following with chemical equation:
(i) Magnesium ribbon (ii) Sodium hydroxides (iii) Crushed eggshells
Answer.

Long Answer Type Questions [5 Markss] –The year 2015

7.State analysis for the following statements:
(i) Tap water conducts electricity whereas purifiedwater does not.
(ii) Dry hydrogen chloride gas does not turn blue litmus red whereas weaken hydrochloric acid does.

(iii) During the summer period, a milkman usually adds a very small amount of baking soda to fresh milk.

(iv) For a dilution of acid, acid is combined into water and not water into acid.
(v) Ammonia is a base but seems not to contain a hydroxyl group.
Answer.
(i) Tap water contains ions that conduct electricity, distilled water does not contain ions.
(ii)Dry HCl does not produce ions but HCl gives H⁺ and Cl^–.
(iii) Baking sodas do not allow milk to turn to lactic acid which makes milk sour.
(iv) Adding water to acid is very exothermic. Therefore water is combined to acid very gently with cooling.
(v) Ammonia dissolved in water and forms H^– Therefore, it is basic in nature.

8.(a) Write the chemical formulas of hydrated copper sulphate and anhydrous copper sulphate. Giving an activity illustrate how these do inter convertibles.
(b) Write chemical names including the formula of plaster of Paris and gypsum.
Answer.
(a)CuSO₄.5H₂O is hydrated copper sulphate. CuSO₄ comprises anhydrous copper sulphate.
Aim: To show crystalline salts include water of crystallisation.

Material Required: CuSO₄.5H₂O (Blue vitriol)), boiling tube, burner, cork,
delivery tube, test tube, clamp stand.
Procedure: 1.1Take 2g of CuSO₄.5H₂O in a boiling tube outfitted in a clamp stand.
2.Observe its colour. Fitt it with cork and delivery tube turned at two right angles which dip into a test tube.
3.Heat crystals in boiling tunnel.
4.Observe gases being condensed in the test tube.
5.Cool the crystals and add few drops of water into them.
Observation: Water vapour get condensed in a test tube and colour
of blue crystals changes into white. On combining water to anhydrous copper sulphate it changes into blue again.
Chemical Reactions :

Conclusion: Crystalline materials have water of crystallization which do lose on heating. When we add water in CuSO₄till a saturated solution Are formed. On cooling, it becomes converted into CuSO₄.5H₂Ocrystals and it shows that both are interconvertible.

9. (a) State the chemical characteristics on which the following uses of baking soda are based:
(i) as an antacids
(ii) as soda acid fire extinguishers
(iii) to make bread and cakes fluffyand spongy.
Answer.
(b) How is washing sodas is obtained from baking soda? Write balanced chemical equation.
(a) (i) It is weakly basic in nature plus naturalize hyperacidity.
(ii)It liberates CO₂ beside H2SO₄, which extinguish fire.
(iii) It liberates CO₂ on heating which makes bread plus cake soft and sponge.

by The Edutech