Metal used to make wires for safety fuses must have
Answer: C
Fuse wire must have high resistivity and a low melting point.
High resistivity makes it the hottest point in the circuit for a given current, and a low melting point makes it part before the wiring behind it is damaged. A tin–lead alloy meets both conditions.
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The uranium fuel used worldwide is mainly in the form of
Answer: B
Reactor fuel is used mainly as uranium dioxide, UO2, pressed and sintered into ceramic pellets.
The oxide is chosen because it has a very high melting point, about 2,865°C, and is chemically stable under irradiation. UF6 is the gas used in enrichment, not in the reactor.
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According to Avogadro's Hypothesis, the smallest particle of an element or a compound, that can exist independently, is called ____
Answer: A
Under Avogadro's hypothesis, the smallest particle of an element or compound that can exist independently is the molecule.
An atom of most elements cannot exist alone - oxygen occurs as O2, nitrogen as N2. Cations and anions are charged particles and are always found paired with an opposite charge.
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The chemical (ethyl mercaptan) added to the otherwise odourless LPG cooking gas for imparting a detectable smell to the gas is a compound of
Answer: A
Ethyl mercaptan (ethanethiol, C2H5SH) is a compound of sulphur, added to LPG to give it a smell.
LPG is odourless, so a leak would otherwise go unnoticed until it reached an explosive concentration. The human nose detects mercaptan at a few parts per billion.
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Which one of the following elements is present in green pigment of leaf?
Answer: D
Magnesium is the metal at the centre of the chlorophyll molecule, the green pigment of the leaf.
Each chlorophyll molecule holds a single magnesium atom in a porphyrin ring, and it is this arrangement that absorbs red and blue light and reflects green. A magnesium-deficient plant turns yellow between the veins.
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Detergents used for cleaning clothes and utensils contain?
Answer: C
Detergents contain sulphonates - usually the sodium salts of long-chain alkyl benzene sulphonic acids.
The sulphonate head does the job the carboxylate head does in soap, but its calcium and magnesium salts are soluble, so a detergent lathers in hard water where soap forms a scum.
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Foot and Mouth disease occurs in -
Answer: B
Foot-and-mouth disease affects cattle and pigs, along with sheep, goats and other cloven-hoofed animals.
It is a highly contagious viral disease that causes blisters in the mouth and on the feet. It rarely kills adult animals but destroys their productivity, so outbreaks are met with slaughter and movement restrictions.
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Thermometer is related to degree in the same way as clock is related to
Answer: C
A thermometer is graduated in degrees as a clock is graduated in hours - in each case the second word names the unit the instrument measures in.
Wall, tower and cock are merely things associated with clocks, not the unit they read.
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What is the scientific name for washing soda?
Answer: A
Washing soda is hydrated sodium carbonate, Na2CO3·10H2O.
It softens water by precipitating the calcium and magnesium as carbonates, so soap can lather. Baking soda is a different compound, sodium bicarbonate.
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Water soluble vitamin include
Answer: D
All three - vitamin C, niacin and riboflavin - are water-soluble.
The water-soluble vitamins are C and the B group. They are not stored in the body to any extent, so a surplus is excreted in urine and a regular supply is needed. Vitamins A, D, E and K are fat-soluble and are stored in the liver.
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