928 + Interview Questions in THE-P-BLOCK-ELEMENTS IN GENERAL AWARENESS Page 19 InterviewSolution

901.	`PF_(5)` is known but `NF_(5)` is not known. Discuss.
Answer» Nitrogen does not have any 2d orbitals in its valence shell. Therefore, it cannot extend its covalency upto five. But in case of phosphorus, vacant 3d orbitals are present. An electron can be promoted from 3s to 3d orbital. As a result, phosphorus can extend its covalency upto five and a molecule of `PF_(5)` can exist.

Discussion

902.	How many grams of CaO are required to neutralise 852 g of `P_(4)O_(10)` ? Draw structure of `P_(4)O_(10)` molecule.
Answer» `underset(=336g)underset(6xx56)(6CaO) " " + " " underset(=284g)underset(4xx31+16xx10)(P_(4)O_(10)) " " to 2Ca_(3)(PO_(4))_(2)` 284 g of `P_(4)O_(10)` need CaO=336 g 852 g of `P_(4)O_(10)` need `CaO=((336g)xx(852g))/((284))=1008 g` For structure of `P_(4)O_(10)`, consult Fig. 3 (Section 4)

Discussion

903.	The oxidation state of central atom in the aniom of compound `NaH_(2)PO_(2)` will be.A. `+3`B. `+5`C. `+1`D. `-3`
Answer» Correct Answer - C `[overset(+1)(H_(2))overset(x-2)(PO_(2))]^(-)` `2(+1)+x+2(-2)=-1` `x-2=-1 " or " x=+1`

Discussion

904.	`P_(4)O_(6)` reacts with water to giveA. `H_(3)PO_(3)`B. `H_(4)P_(2)O_(7)`C. `HPO_(3)`D. `H_(3)PO_(4)`
Answer» Correct Answer - A `P_(4)O_(6)+6H_(2)O("cold") to 4H_(3)PO_(3)`

Discussion

905.	Assertion : In `CO_(2)` molecule C atoms undergoes `sp^(2)` hybridisation Reason : `CO_(2)` molecule has net dipole moment.
Answer» Correct Answer - D In `CO_(2)` molecule, carbon atom undergoes sp hybridisation. `:ddot(O) = C = ddot(O) :` The two sp hybridised orbitals of C-atom overlap with two p-orbitals of O-atoms to make `2 sigma` bonds while other tow electons of C-atoms are involved in `p pi = p pi` bonding with oxygen atom. Hence, it is linear is shape with equal C - O bond lengths and no dipole moment.

Discussion

906.	Boric acid is polymeric due toA. Basic natureB. Acidic natureC. Hydrogen bondsD. Co-ordinate bonds
Answer» Correct Answer - C

Discussion

907.	Thermodynamically the most stable form of carbon is (a) diamond , (b) graphite (c) fullerenes , (d) coal
Answer» (b) Graphite is thermodynamically the most stable form of carbon.

Discussion

908.	A mixture of potassium chlorate ,oxalic acid and sulphuric acid is heated.determine the reaction which element undergoes maximum change in the oxidation number?A. `S`B. `H`C. `Cl`D. `C`
Answer» Correct Answer - 3 `overset(+5)(KCIO_(3))rarroverset(-1)(KCI)+O_(2)` ` overset(3+)((COOH)_(2))rarr overset(+2)CO+overset(+4)(CO_(2))+H_(2)O` ` overset(+6)(H_(2)SO_(4))rarrH_(2)O+overset(6+)(SO_(3))` Thsu maximum change is observed for `Cl`.

Discussion

909.	Highly pure dilute solution of sodium in liquid ammoniaA. shows blue colourB. exhibits electrical conductivityC. produces sodium nitriteD. produces hydrogen gas.
Answer» Correct Answer - A::B

Discussion

910.	What products are expected from the desproprtionation reactin of hypochorous acid ?A. `HClO_(3) " and " Cl_(2)O`B. `HClO_(2) " and " HClO_(4)`C. `HCl " and " Cl_(2)O`D. `HCl " and " HClO_(3)`
Answer» Correct Answer - D `overset(+1)(3HClO) to overset(+5)(HClO_(3)) + overset(-1)(2HCl)`.

Discussion

911.	`2ln(s)+2NaOH(aq)+2H_(2)Oto`
Answer» Correct Answer - No reaction

Discussion

912.	Complete the following reactions: ? (i) `SiO_(2) + 2NaOH to X + H_(2) O` (ii) `SiO_(2) + 4HF to Y + 2H_(2) O` (iii) `Si + 2CH_(3)CI underset(570 K)overset("Cu power")(to) Z` `{:(X,Y,Z):}`A. `{:(Na_(2)SiO_(3), SiF_(4), (CH_(3))_(2) SiCI_(2)):}`B. `{:(H_(2) SiO_(3), SiF_(2), CH_(3) SiCI_(3)):}`C. `(Na_(2)SIO_(3), H_(2)SiO_(3),(CH_(3))_(3) SiCI):}`D. `{:(Na_(2)SiO_(3), H_(2)SiF_(4),(CH_(3))_(2) SiCI_(2)):}`
Answer» Correct Answer - A `SiO_(2) + 2NaOH to underset((X))(Na_(2)SiO_(3)) + H_(2)O` `SiO_(2) 4HF to underset((Y))(SiF_(4)) + 2H_(2) O` `Si + 2CH_(3)CI underset(570 K)overset("Cu.power")(to) (CH_(3))_(2)SiCI_(2)`

Discussion

913.	Number of oxygen atoms shared per `SiO_(4)^(4-)` tetrahedron in single chain silicates are `"_________________"`.
Answer» Correct Answer - 5

Discussion

914.	What is the Oxidationnumber of Xe in mixture of `XeF_(6) and XeF_(4)`?
Answer» Correct Answer - 4

Discussion

915.	How many nitrogen is/are `sp^(2)`. Hybridised in hydrazoic acid?
Answer» Correct Answer - 6

Discussion

916.	Assertion : `SO_(3)` has a planar structure. Reason : S atom in `SO_(3) " is " sp^(2)` hybridised and O-S-O bond angle is `120^(@)`.A. If both assertion and reason are correct and reason is correct explanation for assertion.B. If both assertion and reason are correct but reason is not correct explanation for assertion.C. If assertion is correct but reason is incorrect.D. If both assertion and reason are incorrect.
Answer» Correct Answer - A Reason is the correct explanation for assertion.

Discussion

917.	Assertion: `Cl_(2)` gas belaches the articles permanently. Reason: `Cl_(2)` is a strong reducing agent.A. If both assertion and reason are correct and reason is correct explanation for assertion.B. If both assertion and reason are correct but reason is not correct explanation for assertion.C. If assertion is correct but reason is incorrect.D. If both assertion and reason are incorrect.
Answer» Correct Answer - C Correct reason : `Cl_(2)` is a strong oxidising agent. It bleaches articles permanently in the presence of moisture due to oxidation.

Discussion

918.	A layer of coke is spread over bauxite during the extrection of aluminium. This acts as a/anA. fluxB. slag to remove impuritiesC. reducing agentD. insulation and does not allow heat to excape
Answer» Correct Answer - D The fused electrolyte [a mixture containing alumina, cryolite `(Na_(3)AlF_(6))`, and fluorspar `(CaF_(2))` in the ratio of `20 : 40 : 20`] is covered with a layer of coke to prevent the escape of heat.

Discussion

919.	Give correct order of boiling point of hydride of group 17.
Answer» `HCl lt HBr lt Hl lt HF` Correct order is F₂ < Cl₂ < Br₂ < I2 As we can observe that F₂ and Cl₂is gaseous state in room temperature Br₂ is liquid I₂ is solid So this is clearly visible that how Boiling point is increasing while going down.

Discussion

920.	Which of the following is a noncombustible hydride?A. `NH_(3)`B. `PH_(3)`C. `AsH_(3)`D. `SbH_(3)`
Answer» Correct Answer - 1 Ammonia is neither combustible nor a supporter of combustion. However, it burns in the presence of oxygen to form nitrogen and water. `4NH_(4)+3O_(2)rarr2N_(2)+6H_(2)O`

Discussion

921.	The least stable hydride isA. `PH_(3)`B. `AsH_(3)`C. `SbH_(3)`D. `BiH_(3)`
Answer» Correct Answer - 4 The hydrides show regular graduation in their properties ,The thermal stability of the hybrides decreases (due to decrease fo `Delta_("diss")H^(Ɵ)(E-H)]` as we move from `NH_(3)` to `BiH_(3)`. Thus `NH_(3)` is most stable ,the stability of `PH_(3), AsH_(3)` and `SbH_(3)` decreases progrssively while `BiH_(3)` is the least stable. Order of thermal stability: `NH_(3) gt PH_(3) gt AsH_(3) gt SbH_(3) gt BiH_(3)` `BiH_(3)` is so unstable that it has a half -life of only `20` minutes at ordinary temperatures.

Discussion

922.	Three pairs of compounds are given below. Identify that compound in each of the pairs which has group 13 element in more stable oxidation state. Given reason for your choice. State the nature of bonding also (a) `TlCl_(3),TlCl` (b) `AlCl_(3),AlCl` (c) `InCl_(3),InCl`
Answer» (a) TlCl more stable than `TlCl_(3)` due to inert pair effect. `TlCl_(3)` is less stable and covalent in nature but TlCl is more stable and ionic is nature (b) Due to absence of d-orbitals, Al does not show inert pair effect. Hence, its most stable oxidation state is +3. Thus, `AlCl_(3)` is much more stable then AlCl. Further, in the solid or the vapour state `AlCl_(3)` covalent in nature but in aqueous solutions, it ionises to form A `Al^(3+)(aq) and Cl^(-)(aq)` ions (c) Due to inert pair effect, indium exists in both +1 and +3 oxidation states out of which +3 oxidation state is more stable is more stable than +1 oxidation state. In other words, `InCl_(3)` is more stable than InCl. Being unstable, In Cl undergoes disproportionation reaction `3InCl(aq)rarr2ln(s)+ln^(3+)(aq)+3Cl^(-)(aq)`.

Discussion

923.	Group 16 elements have lower value of first ionisation enthalpy as compared to group 15 elements becauseA. half filled p-orbitals in group 15 elements are more stableB. group 16 elements have smaller size than group 15 elementsC. group 16 elements contain double bond while group 15 elements have triple bondD. group 16 elements have more number of electrons in p-orbitals.
Answer» Correct Answer - A

Discussion

924.	Ripening of fruits can be carried out in the presence ofA. `Na_(2)SO_(4)`B. `NaCl`C. `CaC_(2)`D. `CaCl_(2)`
Answer» Correct Answer - C Acetylene gas required for ripening of fruits is generated by the hydrolysis of calcium carbide: `Ca^(2+)(bar(C )-=bar(C ))+overset(delta)(2H)+overset(delta-)(OH)rarr Ca(OH)_(2)+C_(2)H_(2)`

Discussion

925.	The noble gases have close shell electronic configuration and are monoatomic gases under normal conditions. The low boiling points of the lighter noble gases are due to weak dispersion forces between the atoms and the absence of other inter atomic interactions. The direct reactions of xenon with fluorine leads to a series of compounds with oxidation number `+2, +4 " and" +6. XeF_(4)` reacts violently with water to give`XeO_(3)`. The compounds of xenon exhibit stereochemistry and their geometries can be deduced considering the total number of electrons in valence shell Argon is used in are welding because of its.A. ability to lower reactivity of metalsB. ability to lower the melting point of the solidC. flammabilityD. high calorific value
Answer» Correct Answer - A Argon checks the reactivity of metals towards oxidation by providing an inert atmosphere.

Discussion

926.	Which of the following group `13` elements has the smallest atomic radius?A. `Al`B. `Ga`C. `In`D. `Tl`
Answer» Correct Answer - B The overall order is `Ga lt Al lt In lt Tl` The smaller size of `Ga` relative to `Al` is due to the presence of poor shielding `10` d-electrons in its penultimate shell.

Discussion

927.	Which of the following does not show similarity between boron and aluminium?A. Both form oxides of type `M_(2) O_(3)` when heated with oxygen at high temperatureB. Both dissolve in alkalies and evolve hydrogen.C. Hydroxides of both the elements are basic in nature.D. Both form nitrides of MN type when heated with `N_(2)`.
Answer» Correct Answer - C `B(OH)_(3)` is a weak acid while `AI(OH)_(3)` is amphoteric in nature.

Discussion

928.	In the following reactions `2X+B_(2)H_(6) to [BH_(2)(X)_(2)]^(+){BH_(4)]^(-)` The amine X will not be -A. `NH_(3)`B. `CH_(3)NH_(2)`C. `(CH)_(3))_(2) NH`D. `(CH_(3))_(3)n`
Answer» Correct Answer - D `B_(2)H_(6) + 2N (CH_(3))_(3) to 2BH_(3). N (CH_(3))_(3)`

Discussion

Explore topic-wise InterviewSolutions in .

`PF_(5)` is known but `NF_(5)` is not known. Discuss.

How many grams of CaO are required to neutralise 852 g of `P_(4)O_(10)` ? Draw structure of `P_(4)O_(10)` molecule.

The oxidation state of central atom in the aniom of compound `NaH_(2)PO_(2)` will be.A. `+3`B. `+5`C. `+1`D. `-3`

`P_(4)O_(6)` reacts with water to giveA. `H_(3)PO_(3)`B. `H_(4)P_(2)O_(7)`C. `HPO_(3)`D. `H_(3)PO_(4)`

Assertion : In `CO_(2)` molecule C atoms undergoes `sp^(2)` hybridisation Reason : `CO_(2)` molecule has net dipole moment.

Boric acid is polymeric due toA. Basic natureB. Acidic natureC. Hydrogen bondsD. Co-ordinate bonds

Thermodynamically the most stable form of carbon is (a) diamond , (b) graphite (c) fullerenes , (d) coal

A mixture of potassium chlorate ,oxalic acid and sulphuric acid is heated.determine the reaction which element undergoes maximum change in the oxidation number?A. `S`B. `H`C. `Cl`D. `C`

Highly pure dilute solution of sodium in liquid ammoniaA. shows blue colourB. exhibits electrical conductivityC. produces sodium nitriteD. produces hydrogen gas.

What products are expected from the desproprtionation reactin of hypochorous acid ?A. `HClO_(3) " and " Cl_(2)O`B. `HClO_(2) " and " HClO_(4)`C. `HCl " and " Cl_(2)O`D. `HCl " and " HClO_(3)`

`2ln(s)+2NaOH(aq)+2H_(2)Oto`

Number of oxygen atoms shared per `SiO_(4)^(4-)` tetrahedron in single chain silicates are `"_________________"`.

What is the Oxidationnumber of Xe in mixture of `XeF_(6) and XeF_(4)`?

How many nitrogen is/are `sp^(2)`. Hybridised in hydrazoic acid?

A layer of coke is spread over bauxite during the extrection of aluminium. This acts as a/anA. fluxB. slag to remove impuritiesC. reducing agentD. insulation and does not allow heat to excape

Give correct order of boiling point of hydride of group 17.

Which of the following is a noncombustible hydride?A. `NH_(3)`B. `PH_(3)`C. `AsH_(3)`D. `SbH_(3)`

The least stable hydride isA. `PH_(3)`B. `AsH_(3)`C. `SbH_(3)`D. `BiH_(3)`

Three pairs of compounds are given below. Identify that compound in each of the pairs which has group 13 element in more stable oxidation state. Given reason for your choice. State the nature of bonding also (a) `TlCl_(3),TlCl` (b) `AlCl_(3),AlCl` (c) `InCl_(3),InCl`

Ripening of fruits can be carried out in the presence ofA. `Na_(2)SO_(4)`B. `NaCl`C. `CaC_(2)`D. `CaCl_(2)`

Which of the following group `13` elements has the smallest atomic radius?A. `Al`B. `Ga`C. `In`D. `Tl`

In the following reactions `2X+B_(2)H_(6) to [BH_(2)(X)_(2)]^(+){BH_(4)]^(-)` The amine X will not be -A. `NH_(3)`B. `CH_(3)NH_(2)`C. `(CH)_(3))_(2) NH`D. `(CH_(3))_(3)n`