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Answers
Explanation:
Aim
To study the properties of acids (dil. HCl) and bases (dil. NaOH) by their reaction with
Litmus solution (blue/red)
Zinc metal
Solid sodium carbonate
Materials Required
Test tubes, test tube stand, test tube holder, cork, droppers, boiling tube, match-box, burner, flat bottom flask, thistle funnel, beaker, litmus solution/paper (red and blue), glass rod, zinc granules, freshly prepared lime water, solid sodium carbonate and dil. HCl.
Theory
Acid
An acid is a substance which furnishes H+ ions when it is dissolved in water like HCl. Acids turn blue litmus red and do not affect red litmus.
On reacting with zinc metal, HCl forms a salt, zinc chloride (ZnCl2) and hydrogen gas (H2) is liberated.
CBSE Class 10 Science Lab Manual – Properties of Acids and Bases 1
Hydrogen gas burns in air with a blue flame and produces a pop sound.
CBSE Class 10 Science Lab Manual – Properties of Acids and Bases 2
CBSE Class 10 Science Lab Manual – Properties of Acids and Bases
January 31, 2018 by Veerendra
CBSE Class 10 Science Lab Manual – Properties of Acids and Bases
EXPERIMENT 2(a)
Aim
To study the properties of acids (dil. HCl) and bases (dil. NaOH) by their reaction with
Litmus solution (blue/red)
Zinc metal
Solid sodium carbonate
Materials Required
Test tubes, test tube stand, test tube holder, cork, droppers, boiling tube, match-box, burner, flat bottom flask, thistle funnel, beaker, litmus solution/paper (red and blue), glass rod, zinc granules, freshly prepared lime water, solid sodium carbonate and dil. HCl.
Theory
Acid
An acid is a substance which furnishes H+ ions when it is dissolved in water like HCl. Acids turn blue litmus red and do not affect red litmus.
On reacting with zinc metal, HCl forms a salt, zinc chloride (ZnCl2) and hydrogen gas (H2) is liberated.
CBSE Class 10 Science Lab Manual – Properties of Acids and Bases 1
Hydrogen gas burns in air with a blue flame and produces a pop sound.
CBSE Class 10 Science Lab Manual – Properties of Acids and Bases 2
HCl reacts with sodium carbonate (aqueous/solid) to liberate carbon dioxide (CO2 ) which turns lime water milky due to the formation of calcium carbonate. When excess of CO2 is passed through the solution, the milkiness disappears.
CBSE Class 10 Science Lab Manual – Properties of Acids and Bases 3
Procedure
Litmus Test
Take two test tubes and mark them A and B and put them in a test tube stand. In test tube A take 5 ml of blue litmus solution and in B, take 5mL of red litmus solution (as shown in Fig.1).
CBSE Class 10 Science Lab Manual – Properties of Acids and Bases 4
Using a dropper, add few drops of HCl in each test tube. Stir each tube with separate glass rods B. Note, if there is any colour change occurs in the solutions.
Observation In test tube A, blue litmus turns red and nothing happens to red litmus. Hence, it can be concluded that acids (like HCl) turns blue litmus to red.
Reaction with Zinc (Zn) Metal
Take few zinc granules in a clean and dry test tube.
Add HCl to the test tube containing zinc granules, such that zinc granules are totally submerged in the acid.
Place a cork having glass delivery tube.
A vigorous reaction will take place after 2-3 minutes, with the evolution of a colourless, odourless gas.
On bringing a burning match-stick near the mouth of gas tube, the gas burns with a pale blue flame producing pop sound (as shown in Fig. 2).
CBSE Class 10 Science Lab Manual – Properties of Acids and Bases 5
Reaction 2HCl(aq) + Zn(s) ——> ZnCl2 (aq) + H2↑
Observation Acids (like HCl) liberate hydrogen (H2) gas on reacting with active metals like zinc (Zn) which burn with a pop sound when burning splinter brought near to it.
Reaction with Solid Sodium Carbonate (Na2CO3)
Take a small amount of solid sodium carbonate in a flat bottom flask and some distilled water in it, shake it well.
Take a double bore cork with a thistle funnel and a delivery tube fitted in it, fit it on the open end of the flask.
Now add HCl in the flask through thistle tube.
Reaction taken place with the evolution of colourless and odourless gas. Then gas is passed through freshly prepared lime water with the help of delivery tube (as shown in Fig. 3).
The lime water turns milky.
CBSE Class 10 Science Lab Manual – Properties of Acids and Bases 6
Reaction
Na2CO3(aq)+2HCl(aq) ——–> 2NaCl(aq)+ CO2 ↑ + H2O(l)
Ca(OH)2 (aq) + CO2 ↑ ——–> CaCO3(s) + H2O (l)
CaCO3 (s) + H2O(l) + CO2 (g) ——–> Ca(HCO3)2 (aq)
Observation HCl on reacting with sodium carbonate (Na2CO3) liberates carbon dioxide (CO2) gas which turns lime water milky. On passing the gas in excess of lime water, the milkiness disappears.