In the making of jewels, gold is usually mixed with
Answer: C
Gold is alloyed with copper for jewellery.
Pure 24-carat gold is too soft to hold a setting, so copper - often with a little silver - is added for hardness. 22-carat gold is 22 parts gold in 24, about 91.7 per cent; a higher proportion of copper gives rose gold.
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'Minamata' disease was caused by ?
Answer: B
Minamata disease was caused by mercury.
A chemical plant discharged methylmercury into Minamata Bay in Japan from the 1930s; it accumulated in fish and shellfish, and those who ate them suffered severe neurological damage. The disease was formally identified in 1956.
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The silver mirror test is given by which of the following compounds?
(1) Acetone (2) Acetaldehyde (3) Benzophenone (4) Formic acid
Answer: D
The silver mirror test is given by acetaldehyde and formic acid - that is, 2 and 4.
Tollens' reagent, ammoniacal silver nitrate, oxidises an aldehyde group and deposits metallic silver on the glass: \[\mathrm{RCHO + 2[Ag(NH_3)_2]^+ + 3OH^- \rightarrow RCOO^- + 2Ag\downarrow + 4NH_3 + 2H_2O}\] Formic acid responds because it contains a \(\mathrm{-CHO}\) group as well as \(\mathrm{-COOH}\). Acetone and benzophenone are ketones and do not react.
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If people sleep in closed rooms where charcoal fire is burning, they die due to
Answer: A
They die of carbon monoxide poisoning.
Charcoal burning in a poorly ventilated room has too little oxygen for complete combustion, so it forms CO. Carbon monoxide binds to haemoglobin about 240 times more strongly than oxygen does, forming carboxyhaemoglobin and starving the tissues of oxygen. It is colourless and odourless, so there is no warning.
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Which of the following elements behave chemically both as a metal and a non metal?
Answer: A
Boron behaves both as a metal and as a non-metal.
It is a metalloid: it has a lustrous, hard, semiconducting elemental form, yet its oxide \(\mathrm{B_2O_3}\) is acidic and its chemistry is dominated by covalent bonding. Argon is a noble gas, carbon a non-metal and mercury a metal.
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The ore which is found in abundance in India is
Answer: A
Monazite is the ore found in abundance in India.
The beach sands of Kerala, Tamil Nadu and Odisha hold very large monazite deposits, the source of India's thorium and rare-earth reserves. India has to import fluorspar and much of its copper, and its bauxite and magnetite, though substantial, are not exceptional by world standards.
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The Chemical Symbol of Sodium is
Answer: C
Sodium's symbol is Na.
It comes from the Latin natrium, itself from natron, the naturally occurring sodium carbonate the Egyptians used. Several elements known since antiquity carry Latin symbols in the same way: K for kalium, Fe for ferrum, Ag for argentum.
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Trichloroacetaldehyde was subject to Cannizzaro's reaction by using NaOH. The mixture of the products contains sodium trichloroacetate andanother compound. The other compound is :
Answer: B
The other product is 2,2,2-trichloroethanol.
Chloral, \(\mathrm{CCl_3CHO}\), has no \(\alpha\)-hydrogen, so it undergoes the Cannizzaro reaction: \[\mathrm{2\,CCl_3CHO + NaOH \rightarrow CCl_3COONa + CCl_3CH_2OH}\] One molecule is oxidised to the salt of the acid and the other reduced to the primary alcohol. Chloroform would come from the haloform reaction, which is a different process.
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Which of the following describes the process of glycolysis?
Answer: D
All the above describe glycolysis.
It is the first stage in the oxidation of glucose, and it breaks one molecule of glucose down to two of pyruvate: \[\mathrm{C_6H_{12}O_6 + 2NAD^+ + 2ADP + 2P_i \rightarrow 2\,CH_3COCOO^- + 2NADH + 2ATP + 2H^+ + 2H_2O}\] It takes place in the cytoplasm and needs no oxygen, which is why it is common to both aerobic and anaerobic respiration.
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The element that has the highest first ionization potential is.......
Answer: D
Nitrogen has the highest first ionisation potential of the four.
Ionisation energy rises across a period, so oxygen should exceed nitrogen - but nitrogen's \(2p^3\) sub-shell is exactly half filled and therefore unusually stable, while oxygen's \(2p^4\) has one paired orbital whose electron–electron repulsion makes removal easier. So the order is N > O > C > B.
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