P Block XI

Question 1

The maximum oxidation state shown by a p-block element is equal to the total number of

Answer 1

valence electrons

Question 2

The occurrence of oxidation states two unit less than the group oxidation states are sometime attributed to the …..

Answer 2

inert pair effect

Question 3

Statement 1: Non-metals and metalloids exist only in the p-block of the periodic table
Statement 2: Heaviest element in each p-block group is the most metallic in nature

Answer 3

Both statements are correct

Question 4

The first member of p-block differs from the remaining members of their corresponding group in two major respects.

Answer 4

First is the size and all other properties which depend on size.

The second important difference, which applies only to the p-block elements, arises from the effect of d-orbitals in the valence shell of heavier elements (starting from the third period onwards) and their lack in second period elements

Question 5

The first member of a group differs from the heavier members in its ability to form………. multiple bonds to itself ( e.g., C=C, C≡C, N≡N) and to other second row elements (e.g., C=O, C=N, C≡N, N=O).

Answer 5

pπ - pπ

Question 6

Statement 1: The heavier elements do form π bonds but this involves d orbitals (dπ – pπ or dπ –dπ ).
Statement 2: As the d orbitals are of higher energy than the p orbitals, they contribute less to the overall stability of molecules than does pπ - pπ bonding of the second row elements

Answer 6

Both are correct

Question 7

Statement 1: Boron is a typical non-metal
Statement 2: Aluminium is a metal thus shows no any chemical similarities to boron

Answer 7

Only 1 is correct
Aluminium is metal but shows many chemical similarities to boron

Question 8

Boron is a fairly rare element, mainly occurs as ( name 3 different chemicals)

Answer 8

Orthoboric acid, (H3BO3)
Borax, Na2B4O7·10H2O
Kernite, Na2B4O7·4H2O

Question 9

In India borax occurs in Puga Valley (Ladakh) and Sambhar Lake (Rajasthan).

Answer 9

True

Question 10

The abundance of boron in earth crust is less than……..by mass.

Answer 10

0.0001% by mass

Question 11

There are two isotopic forms of boron

Answer 11

10B (19%)
11B (81%

Question 12

Aluminium is the most abundant element and the third most abundant metal in the earth’s crust
True or false

Answer 12

False

Aluminium is the most abundant metal and the third most abundant element in the earth’s crust

Question 13

Top three abundant elements in earth crust

Answer 13

Oxygen(45.5%)
Silicone (27.7%)
Aluminium (8.3%)
By mass

Question 14

The important minerals of aluminium (2)

Answer 14

Bauxite, Al2O3. 2H2O
Cryolite, Na3AlF6

Question 15

Assertion: Atomic radius of Ga is less than that of Al.
Reason: The presence of additional 10 d-electrons offer only poor screening effect for the outer electrons from the increased nuclear charge in gallium

Answer 15

Both are correct and correct explanation

Question 16

Statement 1: The discontinuity is observed in the ionisation enthalpy values between Al and Ga, and between In and Tl
Statement 2: This is due to inability of d- and f-electrons ,which have low screening effect, to compensate the increase in nuclear charge.

Answer 16

Both are correct and 2 correctly explains 1

Question 17

Statement 1: Down the group, electronegativity first decreases from B to Al and then increases marginally
Statement 2: This is because of the discrepancies in atomic size of the elements.

Answer 17

Both are correct

Question 18

Statement 1: Boron is non-metallic in nature. It is extremely hard and black coloured solid. It exists in many allotropic forms.
Statement 2: Due to very strong crystalline lattice, boron has unusually high melting point.

Answer 18

Both are correct

Question 19

…………… with unusually low melting point (303K), could exist in liquid state during summer

Answer 19

gallium

Question 20

Its high boiling point (2676K) makes it a useful material for measuring high temperatures
Find me

Answer 20

Gallium

Question 21

Assertion: Boron doesn’t form +3 ions and forced to form only covalent compounds
Reason: Due to small size of boron, the sum of its first three ionization enthalpies is very high.

Answer 21

Both are correct and correct explanation

Question 22

Statement 1: In trivalent state, the number of electrons around the central atom in a molecule of the compounds of these elements (e.g., boron in BF3) will be only six.
Statement 2: Such electron deficient molecules have tendency to accept a pair of electrons to achieve stable electronic configuration and thus, behave as Lewis acids

Answer 22

Both are correct

Question 23

It is due to the absence of d orbitals that the maximum covalence of B is…..

Answer 23

4

Question 24

Statement 1: Boron is extremely hard refractory solid of high melting point, low density and very low electrical conductivity
Statement 2: Boron fibres are used in making bullet-proof vest and light composite material for aircraft

Answer 24

Both are correct

Question 25

The……….isotope has high ability to absorb neutrons and, therefore, metal borides are used in nuclear industry as protective shields and control rods

Answer 25

boron-10 (10B)

Question 26

The main industrial application of……… and ………….. is in the manufacture of heat resistant glasses (e.g., Pyrex), glass-wool and fibreglass

Answer 26

borax and boric acid

Question 27

…………. is also used as a flux for soldering metals, for heat, scratch and stain resistant glazed coating to earthenwares and as constituent of medicinal soaps

Answer 27

Borax

Question 28

An aqueous solution of…………is generally used as a mild antiseptic

Answer 28

orthoboric acid

Question 29

Statement 1: Aluminium is a bright silvery-white metal, with high tensile strength. It has a high electrical and thermal conductivity. Statement 2: On a weight-to-weight basis, the electrical conductivity of aluminium is twice that of copper

Answer 29

Both are correct

Question 30

Aluminium forms alloys with( 5 items)

Answer 30

Cu, Mn, Mg, Si and Zn. Its alloys can be given shapes of pipe, tubes, rods, wires, plates or foils and, therefore, find uses in packing, utensil making, construction, aeroplane and transportation industry.

Question 31

The use of……….. and its compounds for domestic purposes is now reduced considerably because of their toxic nature.

Answer 31

aluminium

Question 32

Carbon is the………….. most abundant element by mass in the earth’s crust

Answer 32

seventeenth

Question 33

Naturally occurring carbon contains two stable isotopes…… and ……..

Answer 33

12C and 13C

Question 34

14C is also present and is a radioactive isotope with half-life of ……. years and used for radiocarbon dating

Answer 34

5770 years

Question 35

Tin occurs mainly as…………. and lead as……….

Answer 35

Cassiterite SnO2 Galena PbS

Question 36

Statement 1: There is a considerable increase in covalent radius from C to Si. Statement 2: From Si to Pb a small increase in radius is observed. This is due to the presence of completely filled d and f orbitals in heavier members.

Answer 36

Both are correct

Question 37

Assertion: Small decrease in ∆iH from Si to Ge to Sn and slight increase in ∆iH from Sn to Pb Reason: There is poor shielding effect of intervening d and f orbitals and increase in size of the atom.

Answer 37

Both are correct and correct explanation

Question 38

The electronegativity values for elements from Si to Pb are almost the same.

Answer 38

True

Question 39

All members of group14 are……….. Carbon and silicon are non-metals, germanium is a metalloid, whereas tin and lead are soft metals with………. melting points

Answer 39

solids low

Question 40

Melting points and boiling points of group 14 elements are much lower than those of corresponding elements of group 13.

Answer 40

False Are higher than group 13 elements

Question 41

Assertion: Compounds in +4 oxidation state are generally covalent in nature. Reason: The sum of the first four ionization enthalpies is very high,

Answer 41

Both are correct and correct explanation

Question 42

Germanium forms stable compounds in…… oxidation state and only few compounds in……. oxidation state

Answer 42

+4 state +2 state.

Question 43

Statement 1: Tin forms compounds in both oxidation states (Sn in +2 state is a reducing agent). Statement 2: Lead compounds in +2 state are stable and in +4 state are strong oxidising agents.

Answer 43

Both are correct

Question 44

Assertion: PbI4 does not exist Reason: Because Pb—I bond initially formed during the reaction does not release enough energy to unpair 6s2 electrons and excite one of them to higher orbital to have four unpaired electrons around lead atom.

Answer 44

Both are correct and correct explanation

Question 45

Silicon tetra halide on complete hydrolysis gives

Answer 45

Salicic acid

Question 46

Statement 1: In 1985, third form of carbon known as fullerenes was discovered by H.W.Kroto, E.Smalley and R.F.Curl. Statement 2: For this discovery they were awarded the Nobel Prize in 1996.

Answer 46

Both are correct

Question 47

The C–C bond length is 154 pm in……..

Answer 47

Diamond

Question 48

Layers are held by van der Waals forces and distance between two layers is 340 pm in……..

Answer 48

Graphite

Question 49

C—C bond length within the layer is 141.5 pm in ………

Answer 49

Graphite

Question 50

Fullerenes are made by the heating of graphite in an electric arc in the presence of inert gases such as……./…….

Answer 50

helium or argon

Question 51

The sooty material formed by condensation of vapourised C small molecules consists of mainly…….. with smaller quantity of…….. and traces of fullerenes consisting of……… number of carbon atoms up to 350 or above

Answer 51

C60 C70 even

Question 52

Assertion: Fullerenes are the only pure form of carbon. Reason: They have smooth structure without having ‘dangling’ bonds.

Answer 52

Both are correct and correct explanation

Question 53

C60 molecule has a shape like soccer ball and called……

Answer 53

Buckminsterfullerene

Question 54

Number of 6 membered rings of carbon in Buckminsterfullerene is

Answer 54

20

Question 55

Total number of 5 membered rings of carbon in Buckminsterfullerene

Answer 55

12

Question 56

6 membered ring always fuses with

Answer 56

Another 6 membered or 5 membered ring

Question 57

5 membered ring only fuses with

Answer 57

6 membered ring

Question 58

Buckminsterfullerene has……… vertices and each one is occupied by one carbon atom and it also contains both single and double bonds with C–C distances of 143.5 pm and 138.3 pm respectively

Answer 58

60

Question 59

Spherical fullerenes are also called……….. in short.

Answer 59

bucky balls

Question 60

∆fH (formation) values of diamond and fullerene, C60 are 1.90kJ and 38.1 kJ mol–1, respectively

Answer 60

True

Question 61

……. made from graphite are inert to dilute acids and alkalies

Answer 61

Crucibles

Question 62

Being highly porous………… is used in adsorbing poisonous gases; also used in water filters to remove organic contaminators and in airconditioning system to control odour.

Answer 62

activated charcoal

Question 63

Statement 1: Carbon black is used as black pigment in black ink and as filler in automobile tyres. Statement 2: Coke is used as a fuel and largely as a reducing agent in metallurgy

Answer 63

Both are correct

Question 64

Diamond is measured in carats where one carat is equal to

Answer 64

200mg

Question 65

From silicon to lead the electronegative considerably decreases or there is considerable difference

Answer 65

False The electronegativity becomes almost equal