Explore topic-wise InterviewSolutions in .

Correct CHOICE is (c) Ca2B6O.5H2O

The explanation is: The chemical formula of the colemanite is Ca2B6O.5H2O. 5H2O and it is given that borax OCCURS naturally as tincal in dried up lakes it is also obtained by boiling of mineral colemanite with a SOLUTION of sodium carbonate.

The correct answer is (a) True

The best I can explain: When 1 mole of orthoboric ACID combines with two moles of water it gives an ANION of BORON hydroxide and 1 HYDRONIUM ion, it proves that orthoboric acid is a weak monobasic acid as well as a lewis acid, so the above statement is considered to be true.

Correct choice is (d) borax

Explanation: Tincal is also KNOWN as the pure and natural form of borax, its CHEMICAL formula is given by Na2B4O7.10H2O, it is one of the important minerals of BORON as boron does not occur in the FREE state, it is an ore of boron that EXISTS in the form of hydrated sodium borate.

Correct answer is (C) Green

To EXPLAIN: Borax bead is used for the detection of COLOURED BASIC radicals under the name borax bead test. The action of heat on borax gives Sodium metaborate and boric anhydride which form a GLASSY bead and when it reacts with the basic radical, gives out a colour. For chromium, it is green in colour.

Correct OPTION is (b) SODIUM tetraborate decahydrate

To elaborate: The CHEMICAL name of borax is sodium tetraborate decahydrate, its chemical FORMULA is Na2B4O7.10H2O, and it is made up of two atoms of sodium, four atoms of Boron, seven atoms of Oxygen and 10 moles of WATER.

The correct answer is (a) No

The best EXPLANATION: Boron does not OCCUR in a free state, it occurs in the form of some compounds like borax, Kernite, ORTHOBORIC acid. Elemental Boron can be obtained through many methods like the reduction of boric for oxide with highly ELECTROPOSITIVE metals or by the reaction of Boron halides with HYDROGEN.

Right choice is (b) exothermic

The best explanation: One of the main important uses of diborane is that it is used in ROCKETS as a propellant. The complete COMBUSTION of diborane is highly exothermic. Though, the complete combustion in rockets isn’t possible DUE to the PRODUCTION of boron MONOXIDE.

Correct answer is (b) dimer

Explanation: Borane does not exist so it exists as a dimer in the FORM of diborane. The structure of diborane is in a complex STATE and it has an sp^3 hybrid state. In diborane, a banana bond exists which is 3 Centre 2 electrons Bond.

The CORRECT answer is (c) thallium

The explanation: Thallium is more REACTIVE with their than gallium and indium, due to the formation of unipositive ion Tl^+. Thallium combines with oxygen in the air in order to form thallium oxide, Tl2O is more stable than TL2O3 due to inert pair EFFECT.

The correct option is (a) Thallium

To explain I would say: Both BORON and aluminium do not react with water but amalgamated aluminium REACTS with water and evolves hydrogen. Gallium and indium do not react with cold or hot water but thallium FORMS an OXIDE layer on the SURFACE.

The correct choice is (d) AMORPHOUS

Easiest explanation: CRYSTALLINE Boron is unreactive whereas amorphous Boron is reactive. It REACTS with air at 700-degree centigrade, boron combines with oxygen and nitrogen separately to form its oxide and nitride.

Correct answer is (a) true

Easiest explanation: Both boron of GROUP 13 and SILICON of group 14 form covalent and volatile halides, which fume in moisture AIR DUE to the release of HCl gas. They react with water in order to form boric acid and silicon hydroxide along with hydrochloric gas which is volatile in nature.

The CORRECT answer is (a) METALS

The best I can explain: Boron of group 13 and silicon of group 14 share a DIAGONAL relationship and have many similarities. Both boron and silicon are non-metals, SEMICONDUCTORS and they also form covalent hydrides, therefore, they are not metals.

Correct option is (a) Yes

To explain I would say: Both BORON and silicon FORM covalent HYDRIDES like boranes and silanes respectively. They do react with electropositive METALS and give binary compounds, which yield a mixture of boranes and silanes on HYDROLYSIS.

Correct choice is (a) thallium

Easy explanation: There is a diagonal RELATIONSHIP between boron of group 13 and silicon of group 14 as they resemble each other like LITHIUM of group 1 and magnesium of group 2. There are many CHARACTERISTICS which resemble both boron and silicon.

The correct option is (d) No other metal

For explanation I would say: Boron can be oxidized by concentrated NITRIC acid, while ALUMINIUM BECOMES PASSIVE due to the formation of an oxide layer on the surface. Boron combines with nitric acid in order to produce boric acid and nitrous oxide.

The correct choice is (b) smallest size in the group

The explanation: Boron shows ANOMALOUS behaviour with the other MEMBERS of the group because of the smallest size and the group, highest ionization energy, highest electronegativity in the group, ABSENCE of vacant d- ORBITAL and the ALLOTROPY, while the other members do not show.

The correct OPTION is (a) Aluminium halides acidic character is greater than that of indium halide

The explanation: The halides of group 13 elements behave as LEWIS ACIDS. The correct order of their acidic character decreases from boron, aluminium, gallium and indium. Here halide refers to CHLORINE, bromine and iodine WHEREAS thallium trichloride can act only as an oxidising agent as it decomposes easily.

Correct answer is (b) Boron fluoride

Explanation: All the halides of Boron are trihalides, boron chloride is a COLOURLESS fuming liquid, boron fluoride is a colourless GAS, boron bromide is a colourless fuming liquid and Boron iodide is a white solid at room temperature, all these trihalides of boron are lewis ACIDS.

The correct option is (b) SODIUM TETRA hydroxyl aluminate III

The best I can EXPLAIN: When two moles of aluminium atom is combined with two moles of sodium hydroxide in presence of 6 moles of water, two moles of sodium tetra hydroxyl aluminate III is FORMED along with three moles of the hydrogen MOLECULE.

Correct answer is (d) acidic, basic and amphoteric

Best explanation: On MOVING TOP to BOTTOM of the group, there is a change from acidic to amphoteric and then to basic character, of oxides and HYDROXIDES of group 13 elements. Only boric acid is soluble in water while the other hydroxides are insoluble in water.

Right choice is (b) false

Explanation: Elements of group 13 do not combine directly with HYDROGEN to FORM hydrides, therefore their hydrides have been prepared by INDIRECT methods. An example is that DIBORANE is formed when Boron fluoride is COMBINED with lithium aluminium hydride in the presence of dry Ether.

Right choice is (a) Boron family

Easiest explanation: The elements of the Boron family are less electropositive than the alkaline earth metals due to their smaller size and higher IONIZATION enthalpies. On moving down the GROUP, the electropositive character first increases from Boron to aluminium and then decreases from GALLIUM so THALLIUM due to the presence of d and f orbitals which causes poor shielding.

The correct choice is (a) Ga < In < Tl

Explanation: The correct ORDER of the increased stability of + 1 oxidation STATE in gallium, indium and THALLIUM is that; gallium stability is less than that of indium and indium stability is less than that of thallium.

Correct ANSWER is (d) Formation of sodium borate

For EXPLANATION: Two moles of boron atoms fuse with 6 moles of sodium hydroxide in order to form 2 moles of sodium borate and three moles of hydrogen MOLECULES. Sodium hydroxide is also known as caustic SODA.

Correct choice is (d) Boron nitride

To elaborate: On heating, two moles of boron ATOM combine with one mole of a nitrogen molecule in order to FORM 2 moles of boron nitride. ALUMINIUM ALSO when reacted with nitrogen forms aluminium nitride in the same way.

The correct choice is (b) AlC3

The explanation is: 4 moles of aluminium atom combines with 3 moles of carbon atom on heating, in order to form aluminium carbide. Aluminium carbide is IONIC in nature and it ALSO forms methane with WATER. Its chemical formula is given by AlC3.

Correct answer is (c) boron family

Easiest explanation: The complex formation in the boron family is greater than the S BLOCK elements due to their smaller size and greater charge. So they can FORM complexes more likely than ALKALI METALS and alkaline earth metals.

Right answer is (c) both ionic and COVALENT

To explain I would say: Ionic compound formation’s tendency increases from Boron to thallium. Boron can only FORM covalent COMPOUNDS, whereas ALUMINIUM can form both covalent as well as ionic compounds. Gallium forms MAINLY ionic compounds.

Correct CHOICE is (b) Aluminium > gallium > indium > thallium

The explanation: REDUCING character of the boron family decreases down the GROUP from aluminium to thallium because of the increase in electrode potential VALUE for M^3+/M, therefore, the correct ORDER is given as aluminium > gallium > indium > thallium.

Correct option is (d) Aluminium

The explanation: Boron and aluminium EXHIBIT oxidation state of + 3 only, while gallium, INDIUM and THALLIUM exhibit oxidation states of both +1 and +3. As we move down the group, the tendency to exhibit + 3 Oxidation State decreases this occurs due to the inert PAIR effect.

The correct choice is (d) Is a regular

The best I can explain: On moving down the group, ionization enthalpy DECREASES from Boron to aluminium, but the next ELEMENT gallium has slightly higher ionization enthalpy than aluminium due to the POOR shielding of intervening d-electrons, it again increases in indium and then decreases in the LAST element THALLIUM.

Right ANSWER is (b) False

Easiest explanation: Though the atomic radii increase on going down the group, the RADIUS of gallium decreases UNEXPECTEDLY because of the presence of electrons in the ORBITALS which do not screen the attraction of the nucleus EFFECTIVELY. So the atomic radius of gallium is less than that of aluminium.

Right answer is (c) Group 13 elements

Easiest explanation: Group 13 elements have smaller atomic RADII and ionic radii than those of alkaline earth METALS and alkali metals due to the GREATER EFFECTIVE nuclear CHARGE, atomic radii increases on going down the group with an abnormality at gallium.

Correct OPTION is (d) 2276

To explain I WOULD say: Low melting point of GALLIUM is due to the fact that it consists of Ga2 molecules and gallium REMAINS liquid up to 2276 k. Hence it is used in high-temperature thermometer. Gallium as a chemical symbol that is Ga and its atomic number is given as 31.

Right option is (a) Yes

To explain I would say: The LAST electron enters in the outermost p-orbital in the p block elements, from group 13 to group 18 the entire elements BELONG to p-block, whereas group 13 is called a boron family. It includes the elements boron, aluminum, gallium, INDIUM and thallium.