A bond formed by the transfer of electrons between atoms of the elements is called
Answer: A
This is an ionic bond.
One atom transfers electrons to the other, and the resulting cation and anion are held by electrostatic attraction. It forms between a metal and a non-metal when the electronegativity difference is large - typically above about 1.7.
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The soaps used in shaving cream are
Answer: C
Shaving creams use soft soaps.
Soft soaps are the potassium salts of fatty acids, made with potassium hydroxide instead of sodium. They are more soluble than the sodium (hard) soaps, lather freely and are gentler on skin. Calcium and lead soaps are insoluble and are used as greases and driers.
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Which of the following chemical compounds has the highest boiling point?
Answer: B
Methanol has the highest boiling point.
Methanol boils at 65 °C, dimethyl ether at \(-24\) °C and methane at \(-161\) °C. Methanol and dimethyl ether are isomers of the same formula \(\mathrm{CH_4O}\), but only methanol has an \(\mathrm{-OH}\) group and so can hydrogen bond to its neighbours; breaking those bonds needs much more energy.
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Harmful bacteria in drinking water cannot be destroyed by
Answer: C
Adding caustic soda will not destroy bacteria in drinking water.
Sodium hydroxide is used to correct pH, not to disinfect, and would make the water undrinkable long before it sterilised it. Chlorination, ozonisation and boiling all kill bacteria - chlorine and ozone by oxidation, boiling by denaturing their proteins.
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Which of the following is an Organic Molecule?
Answer: C
Fructose is the organic molecule.
It is \(\mathrm{C_6H_{12}O_6}\), a carbon compound with C–H bonds, which is what defines an organic molecule. Nitrogen and water contain no carbon, and ammonia none either.
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What is the freezing point of water in Celsius?
Answer: A
Water freezes at 0 °C.
That is 32 °F and 273.15 K. The conversion between the first two is \[^\circ\mathrm{F} = \frac{9}{5}\,^\circ\mathrm{C} + 32\]
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Natural Rubber is a Polymer of
Answer: D
Natural rubber is a polymer of isoprene.
It is cis-1,4-polyisoprene, and the all-cis geometry is what gives it elasticity, since the chains cannot pack neatly. Gutta-percha is the trans isomer of the same polymer and is hard and inelastic.
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Which of the Following is an Amorphoussolid?
Answer: A
Quartz glass is amorphous.
It has short-range order but no long-range periodicity, so it has no sharp melting point and its properties are the same in all directions. Chrome alum, silicon carbide and graphite are all crystalline, with regularly repeating lattices.
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Which of the following is a false statement?
Answer: B
The false statement is that bond order is proportional to bond length.
The relation is inverse: the higher the bond order, the more electron density holds the nuclei together and the shorter and stronger the bond. Compare C–C at 154 pm, C=C at 134 pm and C≡C at 120 pm.
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Tetraethyl lead is used as
Answer: B
Tetraethyl lead was used as a gasoline additive.
It is an anti-knock agent: it decomposes in the cylinder to lead and ethyl radicals which interrupt the chain reaction causing pre-ignition, raising the fuel's effective octane number. It has been phased out worldwide because lead is neurotoxic and poisons catalytic converters.
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