31)Chemically dry ice is
solid carbon dioxide solid sulphur dioxide
ice kept at sub-zero temperature ice formed from pure distilled water
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32)A gas which is not present in normal samples of air is
neon carbon dioxide
chlorine helium
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33)A catalyst is a substance which
helps initiate a reaction increase the speed of reaction
decrease speed of reaction stops chemical reaction
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34)Of the following, the content of carbon is minimum in
steel pig iron
cast iron wrought iron
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35)Marsh gas, formed from decaying organic matter and in coal mines is
methane ethane
carbon monoxide carbon dioxide
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36)The acid used in batteries is
acetic acid hydrochloric acid
sulphuric acid nitric acid
Answer :

37)Vinegar is acidic in nature due to the presence of
sulphuric acid citric acid
hydrochloric acid acetic acid
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38)The acid present in lemons and oranges is
acetic acid hydrochloric acid
oxalic acid citric acid
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39)Water for civil supplies is commonly purified by
filtration chlorination
distillation decantation
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40)During fermentation of sugar the chief compound always formed is
methyl alcohol ethylene
ethyl alcohol acetic acid
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41)Fixation of nitrogen implies
the conservation of atmospheric nitrogen into useful compounds the liquefaction of nitrogen
the conservation of nitrogen into amines the solidification of nitrogen of the atmosphere
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42)Wood charcoal is commonly prepared by the process of burning wood
in contact with air in contact with pure oxygen
in contact with nitrogen and inert gases out of contact with air
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43)Animal charcoal is obtained by
burning the bones of animals in contact with air the destructive distillation of bones
burning the bones of animals out of contact with air burning the flesh of animals
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44)The substance that is added to make natural rubber strong and bouncy is
sponge sulphur
chlorine sulphuric acid
Answer :

45)Photographic plates are covered with black paper because
sunlight is easily absorbed by black paper and it helps develop the film the cellulose acetate of the paper must remain fresh
the conservation of silver bromide to metallic silver is essential silver bromide present on the plate is very sensitive to light and black paper prevents contact with light
Answer :

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