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Right option is (b) Air

To explain: INDUSTRIALLY, OXYGEN is isolated by implying the technique of FRACTIONAL distillation of liquefied air. Prior to the main OPERATION, air is cleared and filtered off to remove impurities such as carbon dioxide and water vapor. Oxygen distills off as a liquid at -183°C.

Right answer is (b) False

Easy explanation: Similar to the other elements in group 15 of the periodic table, and especially nitrogen, phosphorus does FORM oxoacids. It forms oxoacids with varying basicity and where the oxidation NUMBER PF phosphorus VARIES too.

Correct CHOICE is (C) 95.9 °C

The best I can explain: Transition TEMPERATURE is where both DOMINANT forms of SULFUR, alpha and beta are stable. For sulfur, the transition temperature is 369K (or 95.9°C), below which alpha-sulfur is most stable and above which, beta sulfur is most stable.

Right option is (b) Phosphorus

To explain: Group 16 of the periodic table consists of five elements viz., Oxygen (O), Sulphur (S), Selenium (Se), TELLURIUM (Te) and Polonium (PO). The elements of this group are commonly known as the oxygen family after the name of its first member.

Right choice is (d) Red PHOSPHORUS

The explanation: Red phosphorus is a relatively stable ALLOTROPE of phosphorus at ROOM temperature. Its ignition temperature(543 K) is much higher than that of white phosphorus(303 K). As a result, it does catch fire easily.

Right answer is (d) 4

For EXPLANATION: In all of the oxoacids of phosphorus, the phosphorus atom is tetrahedrally surrounded by four other atoms or groups. The phosphorus atoms can FORM both DOUBLE and single bonds in its oxoacids.

The CORRECT ANSWER is (d) Aluminium phosphide

To ELABORATE: Metal phosphides such as aluminium phosphide reacts with water to from phosphine and metal hydroxide.

Reaction: AlP + 3H2O → PH3 + Al(OH) 3.

Correct option is (C) Al2O3

The best explanation: Aluminum does not DISSOLVE in nitric acid. This is because treatment with nitric acid results in the formation of a tough OXIDE layer. This oxide layer prevents it from further REACTING with the oxide. HENCE, the compound formed is Al2O3 i.e. aluminum (III) oxide.

Right answer is (C) White phosphorus

The explanation is: White phosphorus EXISTS as P4 units. The four sp^3 hybridized phosphorus atoms LIE at the corners of a regular tetrahedron with an angle of 60 DEGREE. Each phosphorus atom is linked to three other P-atoms by covalent bonds so that each p-atom completes it octet.

Right option is (d) 134°

To elaborate: Ideally, according to its structure, the BOND ANGLE between the TWO oxygen atoms in nitrogen dioxide should be 120°. But, the one LONE electron on the nitrogen atom exerts a less repulsion than NORMAL on the two oxygen atoms. So, they spread out more, to form a bond angle of 134°.

The CORRECT answer is (d) Nitrosyls

Easy explanation: NITRIC oxide (NO) readily forms complexes with TRANSITION metals. These complexes are called nitrosyls. Two important nitrosyl complexes are SODIUM nitroprusside and the nitroprusside ANION.

Correct choice is (d) +1 to +5

Easy explanation: NITROGEN in the ground state has a valency of 3 in its ground state and it has a valency of 5 in its excited state. HENCE, it forms oxides with a WIDE range of oxidation STATES where the oxidation states vary from +1 to +5.

The correct answer is (b) 1.67

Easiest explanation: All NOBLE gases are monoatomic in NATURE due to their stable outer ELECTRONIC configuration. The RATIO of their specific or molar HEAT at constant pressure to the specific or molar heat at constant volume is equal to 1.67, which is the same for all monoatomic gases.

Correct option is (b) RADON

The BEST I can explain: Of all the noble gases, radon is the most soluble in water. Noble gases are non-polar substance, however, when DISSOLVED in water, they are SLIGHTLY soluble. This is due to dipole induced dipole INTERACTIONS.

Correct option is (c) Turn to white finally

Explanation: Chlorine bears bleaching PROPERTIES. When BLUE litmus is subjected to chlorine gas, it first turns RED (due to the acidic NATURE) then it turns white (due to chlorine’s ability to bleach materials).

The correct answer is (c) It is a dibasic acid

Explanation: SULPHURIC acid is an oily liquid and is dibasic in nature. It is a dibasic acid because it contains TWO HYDROGEN atoms which ionize in aqueous SOLUTION to become hydrogen ions. When it reacts with BASES like sodium hydroxide it form two kinds of salts proving its dibasic nature.

The correct choice is (c) MERCURY

The best explanation: Mercury is not included in the list of criteria for monitoring air POLLUTANTS by U.S. – EPA.The criteria air pollutants are CARBON monoxide, lead, ozone, sulfur dioxide, nitrogen oxides, and particulate MATTER

The correct answer is (a) Sulfur dioxide

Easy EXPLANATION: Sulfur dioxide is CODED as preservative E220 when used in Europe. It is known for its antimicrobial properties and ABILITY to prevent OXIDATION. It is responsible for maintaining the colorful appearance and prevents ROTTING.

The CORRECT answer is (b) Sourness

The explanation: Sourness of crude petroleum is a main CHARACTERISTIC CAUSED by the presence of sulfur. Usually, crude petroleum is termed to be sweet if CONCENTRATION of sulfur is less than 0.5%. If it is more, then it is termed as SOUR crude.

Right choice is (B) False

For explanation: The solubility of gases in a liquid is governed by HENRY’s law. It STATES that the partial pressure of a gas in a solution varies directly. In warmer conditions, the gas PARTICLES tend to escape from the water body leading to a lesser AMOUNT of dissolved oxygen required for comfortable aquatic conditions.

The correct choice is (b) SULPHUR

To explain I would say: Sulphur has a stronger tendency for CATENATION than Oxygen. Due to small size, the lone pairs on the Oxygen atoms repel the bond pair of the O-O bond to a greater EXTENT than the lone pairs of ELECTRONS on the Sulphur atoms in S-S bond. As a result, S-S bond is MUCH stronger than O-O bond and hence Sulphur has a much stronger tendency for catenation than Oxygen.

The correct ANSWER is (d) Polonium

Explanation: Oxygen is the most non-metallic ELEMENT of group 16. Sulphur is also a TYPICAL non-metal and TELLURIUM is a metalloid. Polonium is, however, metallic in nature but is radioactive with a SHORT half-life (13.8 days).

Correct CHOICE is (C) They are all diatomic and form univalent ions

To explain I would SAY: Halogens are all diatomic and form univalent ions. All halogens can act as both OXIDIZING and reducing agents and are capable of exhibiting more than ONE stable oxidation state except Fluorine. Hence, option c is the correct statement.

Correct option is (c) It is less soluble in blood

The explanation is: Air CONTAINS a large amount of nitrogen. According to Henry’s law, the solubility of gases INCREASES with increase in pressure. Due to the increased pressure, a large amount of nitrogen dissolves in the blood of a deep-sea DIVER. To prevent this, helium is ADDED to the oxygen cylinders as it is sparingly less soluble in blood.

The correct option is (a) True

The BEST I can explain: Large AMOUNT of impure HCl are obtained in recent YEARS as a by-product from the heavy organic chemical industry. For example, HCl is produced in the CONVERSION of 1,2-dichloroethane to VINYL chloride.

Correct choice is (a) True

To elaborate: Interhalogen compounds are FORMED by IONIC bonds DUE to DIFFERENCES in electronegativity. They are more reactive because they can dissociate easily as they have WEAKER bonds as compared to pure halogen compounds possessing covalent bonds that are formed by the sharing of electrons.

Right option is (c) 2

The explanation: The ‘salt cake’ method is an endothermic REACTION. It is performed in two stages. The first stage INVOLVES the reaction between rock salt and SULPHURIC acid at 420K and in the second stage, the product of the first stage is HEATED to a temperature of 823K so that it further reacts with sulphuric acid.

Correct option is (a) 3%

To explain: Factually, 3% of Earth’s total mass is comprised of elemental SULFUR. Carbon makes u about 0.032% of Earth’s crust and outer MANTLE. On the other hand, iron and MAGNESIUM ACCOUNT for 5% and 2% of Earth’s crust, RESPECTIVELY.

The correct answer is (a) S8, S

Best EXPLANATION: The chemical formula of elemental SULFUR is S, as represented in the periodic table. However, in structural aspects, a MOLECULE of sulfur comprises of 8 sulfur atoms, bond together to FORM S8.

The correct option is (b) Nascent oxygen

To explain I would SAY: Due to its ease in liberating nascent oxygen i.e. [O], ozone is a powerful OXIDIZING agent. Although, it is highly thermodynamically unstable and explosive due to LARGE negative Gibbs energy, the ability of liberating nascent oxygen, it is considered to be one of most powerful BLEACHING agents.

The CORRECT choice is (a) O = O^+ – O^–

The explanation is: According to the Lewis dot-structure, the central oxygen ATOM shares a total of three ELECTRONS as a consequence of which it bears a positive charge. The oxygen to the right FORMS tends to attract a shared pair of electrons towards itself, thereby developing the negative charge.

Correct answer is (d) Salt and WATER

Easy explanation: Amphoteric oxides react with both acids and alkalis. On treatment with alkali solution, they behave as acids and undergo REACTIONS analogous to NEUTRALIZATION, THUS forming salt and water. For e.g. Al2O3 + NaOH → NAALO2 + H2O.

Right CHOICE is (d) Cl2

Easy explanation: PHOSPHORUS trichloride (PCl3) REACTS with chlorine GAS (Cl2) to FORM phosphorus pentachloride (PCl5).

PCl3(g) + Cl2(g) → PCl5(g).

The correct answer is (b) 68% – 32%

Best explanation: Experimentally, it is determined that nitric acid and water form a constant BOILING azeotrope at 68% – 32% by mass composition, RESPECTIVELY. Here, it BECOMES impossible to separate water and nitric acid by DISTILLATION methods. Thus, concentrated sulfuric acid is used for dehydration and removal of water.

The correct option is (a) Fluoride

To elaborate: The fluoride ION is actually not an oxidizing AGENT. DUE to its high electronegativity and high reactivity, it converts WATER to FORM hydroxide ions. The reaction is given by 2F^– + H2O → H – F – H^– + OH^–.

The correct option is (d) NF3

Best EXPLANATION: NF3 is the least basic TRIHALIDE of nitrogen because it has DIFFERENT size and the bond ismorepolar towards nitrogen as it is more electronegative than the remaining HALIDES, which makes electron availabilitymoreon nitrogen(in NF3) than the remaining halides. Thus, it can donate electrons easily and therefore NF3 is least basic.

The CORRECT choice is (c) VANADIUM pentoxide

To explain: After burning SULPHUR in the presence of oxygen the formed Sulphur DIOXIDE needs to be reacted with oxygen to form Sulphur trioxide. It is an exothermic reaction and vanadium pentoxide is USED as the catalyst.

Correct choice is (b) False

Best explanation: Only FLUORINE forms one oxoacid DUE to their high electronegativity and SMALL size. The other halogens form SEVERAL oxoacids, most of them cannot be isolated in pure state. They are stable only in aqueous SOLUTIONS or in the form of their salts.

Correct option is (b) Oxides with pH > -log10[1 x 10^-7]

For explanation I would say: METALS usually form basic oxides. E.g. sodium, potassium,calcium. Meaning, the pH of the salts is greater than 7 on the pH SCALE. pH is calculated as the NEGATIVE logarithm of concentration of hydronium ions. Metals form oxides because upon DISSOLUTION, they release oxide ions which in turn give hydroxide (basic) ions. However, a few metals form oxides which are both acidic and basic, called amphoteric oxides. E.g.zinc, lead.

Correct answer is (b) To kill microorganisms

The best explanation: Chlorine is a very popular disinfecting agent and is widely USED in CONTAINERS to kill microorganisms. In water TREATMENT plants, chlorine gas may be bubbled through to remove TRACE quantities of microorganisms.