Question

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Answer 1

Answer:

Materials Required: CaO(quick lime), distilled water, test tube, beaker, straw.

Procedure:

 1. Take some CaO in a beaker.

2. Slowly add water to CaO taken in the beaker. Pour enough water so CaO is completely immersed.

3. Touch the beaker to note the temperature.

4. Leave it undisturbed for sometime.

5. Take small quantity of it in a test tube and blow exhaled air in it through a straw.

Observations: 

1. When water is added to quick lime, a suspension of slaked lime is formed.

2.On touching the beaker, we feel the warmth.

3.A clear solution appears as the suspension of slaked lime settles down.

4. On blowing exhaled air that contains sufficient CO₂, turns lime water milky.

22.

Pale green to pale yellow.

23

Because iron is more reactive then copper.

a. change in colour

b. formation of salt of iron.

24.

3 BaCl₂ + Al₂(SO₄)₃ ⇒  2 AlCl₃ +  3 BaSO₄.

precipitation reaction of double displacement reaction.

25 .

Because in combination two or more element combine form new compound in combination and in decomposition one compound split into two or more then two elements.

26.

a. decompoition reaction.

AgCl ⇒ Ag⁺ + Cl⁻

Silver chloride has been used as an antidote for mercury poisoning, assisting in the elimination of mercury.

27.

Rancidity is the oxidation of foods containing fats and oils.

1) Rancidity can be prevented by storing food in vacuum containers.

2) Rancidity can be prevented by adding antioxidants to food.

28.

.C₆ H₁₂ O₆ + 6 O₂ --> 6 CO₂ + 6 H₂ O

Exothermic reaction.

Because heat is given out in form of ATP.

29.

when oxidition and reduction take place simultaneously .

A. PbO is Lead (II) Oxide that is reduced to Lead (Pb) and Carbon or C is oxidized to CO2 or Carbon dioxide.

Hence, the oxidized substance is Carbon dioxide or CO2 is the oxidized substance, while Lead (Pb) is the reduced substance in the chemical reaction.

B.

Here MnO₂ is reduced to MnCl₂.

ie., the oxidation no.of Mn is decreased from +4 to -2.

HCl is oxidised to chlorine molecule.

ie.,the OXIDATION-NUMBER of chlorine is increased from -2 to 0.

So MnO₂ is reduced to MnCl₂.