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Right choice is (C) Neon

The EXPLANATION is: Argon is the most abundant noble GAS in the atmosphere, accounting for about 0.934% by volume. Neon is the second most abundant noble gas in the atmosphere (about 0.00182%) FOLLOWED by helium as the THIRD most abundant noble gas (about 0.000524%).

Right choice is (a) HCl

Easiest explanation: HCl, KNOWN as HYDROCHLORIC acid and is not an oxoacid. All OXOACIDS have the acidic hydrogen BOUND to an oxygen ATOM, in HCl the hydrogen is bound to the chlorine atom making it a Lewis acid.

Right ANSWER is (d) RADON

Explanation: Radon is the last-named member of the 18^th group of elements in the periodic table. It is radioactive in natureand as a result, all other noble gases except radon OCCUR in the elemental STATE in the atmosphere.

Right option is (a) High pressure, LOW temperature, excess of oxygen

Easy explanation: High pressure is preferred since the FORWARD reaction proceeds with decrease in NUMBER of moles. Low temperature is preferred because the reaction is highly exothermic and to have maximum YIELD of Sulphur TRIOXIDE, oxygen is used in excess.

Correct answer is (b) Low temperature and high pressure

Explanation: Since the forward reaction is exothermic, LOWER temperatures will FAVOR higher yield. This is in accordance with the LE Chatelier’s principle that an equilibrium tends to attain its original form when external conditions are CHANGED. Since the REACTANT is in gas phase, increasing pressure increases yield.

Right option is (B) Carbon monoxide

To explain I would say: Incomplete combustion of fuels results in the release of carbon monoxide due to limited amount of oxygen burning the FUEL. Carbon monoxide is an asphyxiant, meaning it tends to BLOCK oxygen SUPPLY to cell and CAUSE death due to suffocation.

The correct choice is (d) Antoine Lavoisier

Explanation: In ANCIENT TIMES, sulfur was thought to be fused with mercury and salt towards which alchemists thought it was a metal that could be transmuted. It was Antoine Lavoisier who FIRST thought sulfur was an ELEMENT. However, Humphry Davy believed it contained hydrogen.

The correct option is (c) It has a tough oxide layer

The EXPLANATION: Aluminum is a PASSIVE METAL. MEANING, when formed in nature, it quickly reacts with oxygen in the air to form a tough, non-corrosive oxide layer. This layer prevents aluminum metal from reacting with any other substance.

Right OPTION is (a) H2O

Easy explanation: The hydride of Oxygen, i.e., H2O is a colourless, odourless liquid while the hydrides of all the other group 16 elements are UNPLEASANT, foul smelling, poisonous gases. H2O has the highest boiling point of 373 K amongst the hydrides of group 16 elements.

Right option is (c) -2

The best I can explain: Oxygen atom is the most stable in its -2 OXIDATION state. Here, it gains 2e^– to COMPLETE its octet and obtain the noble gas configuration of [NE]. Rarely does oxygen show +1 and -1 oxidation states. The -1 state is displayed in PEROXIDES. E.g. H2O2. It shows +1 in oxygen (I) fluoride, OF2.

Right option is (a) True

Easiest explanation: Oxygen also occurs as OZONE (O3), an allotrope of oxygen, in the upper ATMOSPHERE which protects us from the harmful RADIATIONS of the SUN. Ozone is a pale blue gas with a distinctively pungent smell.

Right choice is (c) 48

To explain I WOULD say: 1 mole of SULFUR, S8 requires 48 moles of concentrated nitric ACID. The reaction is GIVEN byS8 + 48HNO3 → 8H2SO4 + 48NO2 + 16H2O. 10, 4 and 20 moles of concentrated nitric acid is required to produce iodic acid, carbon dioxide and phosphoric acid from 1 mole of iodine, carbon and phosphorus, RESPECTIVELY.

Right CHOICE is (b) False

The explanation is: PHOSPHINE ACTS as a Lewis base and reacts with acidic SPECIES to form phosphinium SALTS.

PH3 + HBr → PH4Br

Phosphine reacts with hydrogen bromide to form phosphinium salts which is a property of a base.

The CORRECT CHOICE is (b) It is a weak oxidizing agent

For explanation: NITRIC acid is a very weak reducing agent since it has a polar O – H bond. This breaks to donate the H^+ ion which is why it is a strong oxidizing agent and a strong acid. Since there is only ONE cleavable O – H bond, the basicity of nitric acid is unity (one HNO3 molecule can donate only 1 H^+ ion). It exists as a planar molecule in vapor phase.

Right option is (a) Hyponitric ACID

Best explanation: Hyponitric acid does not exist. The rest three mentioned are commonly occurring oxoacids of nitrogen. Hyponitrous acid, H2N2O2 is an isomer tautomer of nitramide, with the STRUCTURE of the FORMER being HON = NOH. Nitrous acid, HNO2 is usually FORMED in the atmosphere prior conversion to NITRIC acid. It is highly unstable.

Correct OPTION is (d) Low temperature, high pressure

To explain: Following the Le Chatelier’s PRINCIPLE, since the forward reaction is exothermic (i.e. N2 + 3H2 → 2NH3), low temperatures would increase the RATE of reaction in TURN producing more ammonia. In addition to this, since the total number of molecules on the product side lesser, high pressures will increase the rate of reaction.

The correct choice is (d) Leiden frost effect

To elaborate: The Leiden frost effect creates a small layer of insulating vapor layer just at the instant when the LIQUID particle strikes a SURFACE comparatively a lot hotter than liquid. Liquid nitrogen is at-196°C and the human BODY at 38°C. This insulating vapor layer prevents the liquid to further COME in CONTACT with the body which then slips away.

The correct option is (d) Non-aqueous solvents

To explain I would say: If we COME to the uses of the interhalogen compounds, then one of its main uses is to ACT as the halogenating agent, i.e., they are used to form other halogen compounds like BRF5. Interhalogen compounds of fluorine are very USEFUL fluorinating agents.

The correct option is (b) PREPARING TNT

For explanation: Hydrochloric acid reacts with metals to form their respective CHLORIDES and so, is used in the manufacture of metal chlorides. Aqua regia is made USING hydrochloric acid and nitric acid. Hydrochloric acid is ALSO used for EXTRACTING glue from bones.

The correct choice is (a) ns^2np^5

To explain: The ELEMENTS of group 17 have seven electrons in the valence SHELL and hence their general electronic configuration is ns^2np^5, i.e., ns^2npx^2npy^2npz^1 where n = 2-6. Thus, they contain one electron less than the NEAREST inert GAS configuration.

Right OPTION is (a) True

Easiest explanation: Halogens are highly reactive ELEMENTS and hence do not occur in the free STATE or native state. They mainly occur in the combined state in the form of their halide (X^–) salts although iodine ALSO occurs as iodate (IO3^–).

The correct option is (a) HO3SOOSO3H

The best EXPLANATION: Marshall’s ACID is the common name for peroxydisulfuric acid. It is prepared by the reaction between chlorosulfuric acid and hydrogen peroxide. Another method includes the electrolysis of concentrated sulfuric acid (60% – 70%) with platinum ELECTRODES at high current DENSITY and voltage.

The correct answer is (c) To increase the yield

To elaborate: SULFUR dioxide is passed twice to increase the yield and conversion to form more sulfur trioxide. In the first pass, only 63-65% of sulfur dioxide is CONVERTED to sulfur trioxide. When passed for the second time, the conversion increases to 80% HENCE increasing the yield of sulfur trioxide. This can be repeated to achieve a maximum 99% conversion.

Right answer is (b) Sulfurous acid

For explanation I would say: Sulfurous acid CAUSES acid rain. When SULFUR is burned or sulfur compounds are released into the atmosphere, it rises up in the atmosphere to mix with water vapor to FORM sulfurous acid, H2SO3 or it reacts with more oxygen to form sulfur trioxide which forms SULFURIC acid, H2SO4 on MIXING with vapor and precipitating as acid rain.

Correct answer is (a) Peroxodiphosphoric ACID

Easy explanation: The OXIDATION state of PHOSPHORUS in peroxodiphosphoric acid is +5. The oxidation state of phosphorus in hypo phosphorus acid is +1, in ortho phosphorous acid is +3 and in hypo phosphoric acid is +4.

Correct option is (c) The atomic radii of the elements of group 16 are larger than those of the corresponding elements of group 15

The BEST I can explain: When you move across the PERIODIC table, from LEFT to right, the atomic size of the respective elements decreases due to increase in nuclear CHARGE. Therefore, the atomic radii of the elements of group 16 are smaller than those of the corresponding elements of group 15.

The correct CHOICE is (B) 523 K

For explanation: At a temperature of about 523 K, orthophosphoric acid forms pyrophosphoric acid. At 523 K, two molecules of ortho phosphoric acid (H3PO4) REACT with each other to FORM pyro phosphoric acid and water.

The CORRECT choice is (a) By reacting calcium PHOSPHIDE with WATER or dilute HCl

To elaborate: Phosphine is prepared by the reaction of calcium phosphide with water or dilute HCl.

With water: Ca3P2 + 6H2O → 2PH3 + 3Ca(OH) 2

With dilute HCl: Ca3P2 + 6HCl → 2PH3 + 3CaCl2.

Right choice is (a) True

Explanation: Yes, red phosphorus SUBLIMES on HEATING giving vapours which are the same as by WHITE phosphorus. When these vapours are condensed, white phosphorus is obtained. This GIVES us simple method of reconverting red phosphorus into white phosphorus.

The correct answer is (a) NH2

Best EXPLANATION: Ammonia is a tri-HYDRIDE of NITROGEN. It is a colorless gas with a highly pungent smell that causes NASAL irritation. It is the most stable hydride of any ELEMENT in group 15.

The correct option is (c) 3.82 days

For explanation I WOULD say: Half-life of a RADIOACTIVE substance refers to the AMOUNT of time that it TAKES for half of the radioactive atoms in a sample to decay into a more stable form. Radon has a half-life of 3.82 days.

Right answer is (a) True

The EXPLANATION: Helium is the second element in the periodic table and has an atomic number of 2. Helium is formed as the result of the fusion of TWO hydrogen atoms. Helium is the most abundant gas in the universe (23% as COMPARED to 76% of hydrogen).

The correct choice is (a) False

The explanation: The ACIDIC strength of the oxoacids of the same HALOGEN can be determined by the oxidation number of the halogen in the COMPOUND. In HCLO4 the oxidation number of chlorine is +7 and in HClO the oxidation number of chlorine is +1. So, the acidic strength of HClO4 is GREATER than HClO.

Right answer is (a) ACIDIFY the given compound and add silver nitrate

The explanation is: The standard, universal QUALITATIVE test for detecting PRESENCE of chloride is CARRIED out by acidifying the solution and then adding silver nitrate. If chloride ions are present, a thick white ppt. is produced.

Correct option is (b) Diatomic

The EXPLANATION: Each halogen has one electron less than the NEAREST inert gas. As a result, halogens are very reactive elements. They readily share their single unpaired electron with other ATOMS to form covalent bonds. THUS, all halogens exist as diatomic molecules.

The correct option is (d) Carnallite

The EXPLANATION: FLUORINE occurs as insoluble FLUORIDES to the EXTENT of 0.07% in the earth’s crust. The chief minerals of fluorine are:

FLUORSPAR, CaF2

Cryolite, Na3AlF6

Fluoroapatite, CaF2.3Ca3(PO4)2

The correct choice is (c) Sodium sulfate

To explain: Glauber salt is the famous name for the deca-hydrate sulfate salt of sodium. Its chemical FORMULA is Na2SO4.10H2O. It is also known as mirabilite. It is WIDELY used as LAXATIVES in several medications and HELPS removing excess DOSES of drugs from human body, such as paracetamol.

The correct answer is (d) The heat of dissolution is very high and potentially dangerous

The EXPLANATION is: The reaction between sulfur trioxide and water is HIGHLY exothermic and releases great amount of energy that no plant, currently, has the ability to withstand. Due to POTENTIAL RISKS of explosion and fire hazard, sulfur trioxide is not dissolved in water but treated with sulfuric acid to produce oleum. This can be diluted to DESIRED concentrations.

The correct answer is (c) 4.2 K

Best explanation: The melting and boiling points of noble GASES are very low. This is because the atoms are held TOGETHER by very weak Van der Waals forces of ATTRACTION in both liquid and SOLID states. Helium has the lowest boiling point, equal to 4.2 K, among all known substances.

Right ANSWER is (a) Acids

To explain I would say: The oxygen compounds of sulfur represent the class of ‘oxoacids’ of sulfur. Generally, a non-metallic oxide is usually ACIDIC in NATURE (given that exceptions like CO, N2O, NO). EXAMPLES include SULFUROUS acid (H2SO3), sulfuric acid (H2SO4) and many more.

The correct ANSWER is (d) Helium

The best explanation: Neon, argon, krypton and xenon are obtained by fractional distillation of air. Fractional distillation of liquid air gives oxygen, nitrogen and a MIXTURE of noble GASES. The individual noble gases are then separated by adsorption over coconut CHARCOAL which adsorbs DIFFERENT gases at different temperatures.

Right answer is (c) sp^3d

For explanation I WOULD say: The structure of all INTERHALOGEN compounds of the type XX’3involves sp^3d hybridization of the central atom X and hence they have trigonal bipyramidal GEOMETRIES or T-shaped molecules (ALSO called as see-saw).

Correct option is (b) Aryl SULFONYL Chloride

The best explanation: When aryl DIAZONIUM SALTS are treated with SULFUR dioxide in presence of CuCl and acetic acid, it forms aryl sulfonyl chloride Diazonium salts are highly UNSTABLE intermediates due to the N≡N^+ bond.

Correct answer is (c) Sulfur dioxide

Explanation: In presence of water, SO2 is able to decolorize substances. Specifically, it is used as a reducing bleach for papers ALTHOUGH the bleaching EFFECT does not last very LONG. It is an ESSENTIAL process to REMOVE lignin, a natural element that causes paper to turn brown.

Correct choice is (C) Chlor-alkali process

Easiest explanation: ALTHOUGH Deacon process INVOLVES release of chlorine gas as a BYPRODUCT, the chief PURPOSE of the deacon process is used to manufacture alkalis. Chlorine is best produced by the chloralkali process, which is the electrolysis of brine, producing hydrogen and chlorine gases as by products.

Correct choice is (C) Astatine

Easiest EXPLANATION: Astatine (Atomic No. = 85, Symbol-At) is RADIOACTIVE and hence OCCURS in nature only in traces. Therefore, not much is known about its chemistry, though it might be expected to be a metalloid.