1.When dilute HCl is added to zinc pieces taken in a test tube
(a)No change takes place
(b)the colour of the solution becomes yellow.
(c)A pungent smelling gas gets liberated.
(d)small bubbles of H2 gas appear on the surface of zinc pieces
Ans. (d) Small bubbles of H2 gas Appear on the surface of zinc pieces.
2 .PbS reacts with ozone (O3) and forms pbso4. As per the balanced equation, molecules of ozone required for every one molecule of PbS is / are
(a)4
(b)3
(c)2
(d)1
Ans. (a) 4
3.In the reaction PbO + C Pb + CO
(a)Pbo is oxidised
(b)C act as an oxidising agent
(c)C act as a reduction agent
(d)Reaction does not represent redox reaction.
Ans. (c) C act as a reduction agent
4 .A substance which oxidizes itself and reduces other is known as (a)Oxidising agent
(b)reducing agent
(c)Both (a) and (b) (d)None of these.
Ans. (b) reducing agent
5.Take about 5 ml of dil. HCl in a test tube and add a few pieces of fine granules to it. Which gas is evolved?
(a)Chlorine
(b)Hydrogen
(c)HCl
(d)Nitrogen
Ans. (b) Hydrogen
6.Dissolving suger is an example of
(a)Physical change
(b)Chemical change
(c)Redox Reaction
(d)None of these.
Ans. (a) Physical change
7 .Way do diamond and graphite, the two allotropic forms of carbon evolve different amounts of heat on combustion?
Ans. Diamond and graphite are the two allotropes of carbon but they do not evolve same amount of heat on combustion because they differ in the arrangement of carbon atoms and also their shapes one different.
8 .What is the sole of oxidizing agent is a reaction?
Ans. The oxidizing agent supply the oxygen in a reaction or it removes the hydrogen.
9 .What happens chemically when quick lime is added to water?
Ans. When quick lime is added to water calcium hydroxide (slaked lime) is formed with a
hissing sound and lot of heat is evolved during the reaction. The reaction involved is CaO (s) + H2O(Quick Lime) Ca (OH) 2 (s) + Heat (Shaked Lime)
10 .Why a combustion reaction an oxidation reaction?
Ans. Combustion reaction because it is always carried out in the presence of air or oxygen for e.g. CH4 (g) + 2O2 (g) Co2 (g) +2H2O (l)
11 .Why are food particle preferably packed in aluminum foil?
Ans. Aluminium foil do not corrode in atmosphere even if kept for a long time because a protective coating of aluminium oxide (Al2O3) is formed on the surface of the foil and stops any further reaction of the metal with air and water thus food particles do not get spoiled.
12 .What happens to lime water when Co2 gas is bubbled through it in excess?
Ans. When CO2 gas is bubbled through lime water in excess then initially it becomes milky but then its milkiness disappears.
(a)No change takes place
(b)the colour of the solution becomes yellow.
(c)A pungent smelling gas gets liberated.
(d)small bubbles of H2 gas appear on the surface of zinc pieces
Ans. (d) Small bubbles of H2 gas Appear on the surface of zinc pieces.
2 .PbS reacts with ozone (O3) and forms pbso4. As per the balanced equation, molecules of ozone required for every one molecule of PbS is / are
(a)4
(b)3
(c)2
(d)1
Ans. (a) 4
3.In the reaction PbO + C Pb + CO
(a)Pbo is oxidised
(b)C act as an oxidising agent
(c)C act as a reduction agent
(d)Reaction does not represent redox reaction.
Ans. (c) C act as a reduction agent
4 .A substance which oxidizes itself and reduces other is known as (a)Oxidising agent
(b)reducing agent
(c)Both (a) and (b) (d)None of these.
Ans. (b) reducing agent
5.Take about 5 ml of dil. HCl in a test tube and add a few pieces of fine granules to it. Which gas is evolved?
(a)Chlorine
(b)Hydrogen
(c)HCl
(d)Nitrogen
Ans. (b) Hydrogen
6.Dissolving suger is an example of
(a)Physical change
(b)Chemical change
(c)Redox Reaction
(d)None of these.
Ans. (a) Physical change
7 .Way do diamond and graphite, the two allotropic forms of carbon evolve different amounts of heat on combustion?
Ans. Diamond and graphite are the two allotropes of carbon but they do not evolve same amount of heat on combustion because they differ in the arrangement of carbon atoms and also their shapes one different.
8 .What is the sole of oxidizing agent is a reaction?
Ans. The oxidizing agent supply the oxygen in a reaction or it removes the hydrogen.
9 .What happens chemically when quick lime is added to water?
Ans. When quick lime is added to water calcium hydroxide (slaked lime) is formed with a
hissing sound and lot of heat is evolved during the reaction. The reaction involved is CaO (s) + H2O(Quick Lime) Ca (OH) 2 (s) + Heat (Shaked Lime)
10 .Why a combustion reaction an oxidation reaction?
Ans. Combustion reaction because it is always carried out in the presence of air or oxygen for e.g. CH4 (g) + 2O2 (g) Co2 (g) +2H2O (l)
11 .Why are food particle preferably packed in aluminum foil?
Ans. Aluminium foil do not corrode in atmosphere even if kept for a long time because a protective coating of aluminium oxide (Al2O3) is formed on the surface of the foil and stops any further reaction of the metal with air and water thus food particles do not get spoiled.
12 .What happens to lime water when Co2 gas is bubbled through it in excess?
Ans. When CO2 gas is bubbled through lime water in excess then initially it becomes milky but then its milkiness disappears.
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