Liquefied Petroleum gas (LPG) consists of mainly?
Answer: B
LPG consists mainly of propane and butane, with some methane in the mixture.
These gases liquefy under modest pressure at ordinary temperature, so a great deal of fuel is stored in a small cylinder. Ethyl mercaptan is added to give the odourless mixture a warning smell.
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Which one is an alkaline among the following?
Answer: B
Ammonia is alkaline. Dissolved in water it forms ammonium hydroxide, giving a solution of about pH 11.
Vinegar and acid rain are acidic, and saliva is very close to neutral at about pH 6.7.
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Which science is sometimes called the ‘central science’?
Answer: B
Chemistry is called the central science, because it links the physical sciences to the life and applied sciences.
Physics explains why chemistry works, and chemistry in turn explains biology, geology and materials science - so it sits in the middle of the chain of explanation.
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Epoxy resins is used as?
Answer: D
Epoxy resins are used as adhesives, and also as coatings and casting materials.
They are supplied as two parts - resin and hardener - that cross-link on mixing into a rigid solid, bonding strongly to metal, glass and ceramics.
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The major ingredient of leather is?
Answer: A
Collagen is the major ingredient of leather. It is the fibrous protein of animal skin, and tanning stabilises it by cross-linking the fibres so they no longer rot or dry hard.
Collagen is also the commonest protein in the body, forming the framework of skin, tendon, bone and cartilage.
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Permanent hardness of water, due to sulphates of the metal, can be destroyed by the use of?
Answer: C
Permanent hardness due to sulphates is removed by zeolites - the permutit process.
Zeolite is a sodium aluminium silicate that exchanges its sodium ions for the calcium and magnesium in the water. When exhausted it is regenerated by flushing with brine, so it can be used indefinitely.
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The fastest acting enzyme in the biological kingdom is?
Answer: B
Carbonic anhydrase is the fastest known enzyme, converting up to a million molecules of carbon dioxide a second.
It catalyses \( \mathrm{CO_2 + H_2O \rightleftharpoons H_2CO_3} \) in the red blood cells, which is how carbon dioxide is carried from the tissues to the lungs fast enough to keep up with respiration.
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The colour of Emerald is?
Answer: A
Emerald is deep green. It is a variety of the mineral beryl, and its colour comes from traces of chromium and vanadium.
Aquamarine is the pale blue-green variety of the same mineral. Emerald is one of the four precious stones, with diamond, ruby and sapphire.
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Lightning causes rainfall because
Answer: A
Lightning helps produce rain because the enormous energy of the discharge activates the water molecules in the cloud, promoting condensation around the ions it creates.
The same discharge also combines atmospheric nitrogen and oxygen into nitrogen oxides, which dissolve in the rain and reach the soil as nitrates - a natural fertiliser.
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A carbon tetrachloride fire extinguisher should not be used in a closed room because it produces a poisonous gas called
Answer: A
A carbon tetrachloride extinguisher must not be used in a closed room because the hot vapour reacts with air and moisture to give phosgene (COCl2), a gas used as a chemical weapon in the First World War.
For this reason CCl4 extinguishers have been withdrawn almost everywhere.
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