Question Set B

p - Block Elements - II

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Questions:

Multiple Choice Question

7 x 1 = 7

Oxidation states of P in H₄P₂O₅, H₄P₂O₆, H₄P₂O₇ are respectively _______.

(a)

+3, +4, +5

(b)

+3, +5, +4

(c)

+5, +3, +4

(d)

+5, +4, +3

Repeated use of which one of the following fertilizers would increase the activity of the soil_______.

(a)

Ammonium sulphate

(b)

Superphosphate of lime

(c)

Urea

(d)

Potassium nitrate

Which one of the following orders is not in accordance with the property stated against it?

(a)

F₂> CI₂> Br₂> I₂: Bond dissociation energy

(b)

HI > HBr > HCI > HF: Acidic property in water

(c)

F₂> Cl₂> Br₂> l₂: Oxidising power

(d)

F₂> Cl₂> Br₂> l₂: Electronegativity

The hybridisation and shape of SF₆ is respectively?

(a)

sp³d², square planar

(b)

sp³d², octahedral

(c)

sp³d see-saw

(d)

sp³d, trigonal bipyramidal

When copper is heated with conc HNO₃ it produces ________.

(a)

Cu(NO₃)₂, NO and NO₂

(b)

Cu(NO₃)₂ and N₂O

(c)

Cu(NO₃)₂ and NO₂

(d)

Cu(NO₃)₂ and NO

The correct order of the thermal stability of hydrogen halide is_______.

(a)

HI > HBr > HCl > HF

(b)

HF > HCl > HBr > HI

(c)

HCl > HF > HBr > HI

(d)

HI > HCl > HF > HBr

The basicity of pyrophosphorous acid ( H₄P₂O₅) is _______.

(a)

(b)

(c)

(d)

Generic 2

4 x 2 = 8

Why does ozone act as a powerful oxidising agent?

What is the reaction of Phosphorous with alkali?

10.

Suggest a reason why HF is a weak acid, whereas binary acids of the all other halogens are strong acids.

11.

Explain why fluorine always exhibit an oxidation state of -1?

Generic 3

4 x 3 = 12

12.

Predict the product
(i) PCI₅+ C₂H₅OH \(\longrightarrow \)?
(ii) P₄+ SO₂Cl₂\(\longrightarrow \) ?
(iii) POCl₃ + H₂O \(\longrightarrow \) ?
(iv) HBr + PH₃\(\longrightarrow \) ? :,
(v) PCl₃+ H₂O\(\longrightarrow \) ?

13.

Write the order of thermal stability of the hydrides of group 16 elements.

14.

Why do noble gases form compounds with fluorine and oxygen only?

15.

Write the reason for the anomalous behaviour of Nitrogen.

Assertion and reason

2 x 2 = 4

16.

Assertion: PH₅ is not possible.
Reason: -5 oxidation state of phosphorus is not possible.
Codes:
a) Both assertion and reason are true and reason is the correct explanation of the assertion
b) Both assertion and reason are true and reason is not the correct explanation of the assertion.
c) Assertion is true but reason is false
d) Both assertion and reason are false

17.

Assertion: Noble gases have highest ionization energies in their respective periods.
Reason: The outermost sub-shell of noble gases in which electron enters is completely filled.
Codes:
a) Both assertion and reason are true and reason is the correct explanation of the assertion
b) Both assertion and reason are true and reason is not the correct explanation of the assertion
c) Assertion is true but reason is false
d) Both assertion and reason are false

One or Two Words / Correct Statement

2 x 1 = 2

18.

About "White phosphorous"
I. It's ignition temperature in very high.
II. It glows in the dark due to oxidation.
III. White phosphorous is poisonous in nature.
IV. It has pungent smell.
a) II and III only
b) II and IV only
c) II, I, IV and III
d) I, II, III and IV

19.

About" Ammonia"
I. Ammonia is formed by the hydrolysis of urea.
II. It is heavier than air.
III. It can readily liquefied by at about atmospheric pressure.
IV. Liquid ammonia resembles water in its physical properties.
a) I, III and IV only
b) II, I, III and IV
c) II, I, IV and III
d) I, II, III and IV

Find the wrong statement

2 x 2 = 4

20.

Which among the following is mismatched regarding the shape?
a) XeF₄ - square planar
b) XeOF₄ - square pyramidal
c) XeF₆ - Distorted octahedral
d) XeO₃ - Bent T shape

21.

a) Ammonia molecule is pyramidal in shape
b) Ammonia and water are linked by hydrogen bonds.
c) Nitric acid decomposes on exposure to sunlight.
d) Metal nitrate is formed with the release of nitrogen.

Generic 5

2 x 5 = 10

22.

An element A occupies group number 15 and period number 3, reacts with chlorine to give compound B. The compound B on hydrolysis gives a dibasic acid C. The compound C on heating undergoes auto oxidation and reduction to give a tribasic acid D. Identify the elements A compounds B, C and D. Write the reactions.

23.

Mention the uses of helium.

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Answers Key:

Multiple Choice Question

7 x 1 = 7

(a)
+3, +4, +5

(a)
Ammonium sulphate

(a)
F₂> CI₂> Br₂> I₂: Bond dissociation energy

(b)
sp³d², octahedral

(b)
HF > HCl > HBr > HI

(b)
2

Generic 2

4 x 2 = 8

(i) Ozone acts as a powerful oxidizing agent because ozone liberates nascent oxygen very easily on decomposition.
\({ O }_{ 3 }\longrightarrow { O }_{ 2 }+\left[ O \right] \)
(ii) This nascent or atomic oxygen brings about the oxidations it is very reactive.

Yellow phosphorus reacts with alkali on boiling in an inert atmosphere liberating phosphine. Phosphorus acts as a reducing agent.
\({ P }_{ 4 }+NaOH+{ H }_{ 2 }O\longrightarrow \underset { Sodiumhypophosphite }{ { 3NaH }_{ 2 }{ PO }_{ 2 } } +\underset { Phosphine }{ { PH }_{ 3 } } \uparrow \)

10.

HF is a weak acid i.e. 0.1 M solution is only 10% ionised, but in 5M & 15M solution, HF is stronger acid due to chemical equilibrium.
\(\mathrm{HF}+\mathrm{H}_{2} \mathrm{O} \rightleftharpoons \mathrm{H}_{3} \mathrm{O}^{+}+\mathrm{F}^{-} \)
\(\mathrm{HF}+\mathrm{F}^{-} \rightleftharpoons \mathrm{HF}_{2}^{-}\)

11.

(i) Fluorine is most electronegative atom.
(ii) It has only one unpaired electron.

Generic 3

4 x 3 = 12

12.

(i) PCI₅+ C₂H₅OH \(\longrightarrow \) C₂H₅CI + POCl₃ + HCI
(ii) P₄+ 10SO₂Cl₂\(\longrightarrow \) 4PCI₅ + 10SO₂
(iii) POCl₃ + 3H₂O \(\longrightarrow \) H₃PO₄ + 3HCI
(iv) PH₃ + HBr\(\longrightarrow \) PH₄Br
(v) PCl₃+ 3H₂O\(\longrightarrow \) H₃PO₃ + 3 HCI

13.

(i) The thermal stability of hydrides of group 16 elements is directly proportional to the bond dissociation enthalpy of H- E bond.
(ii) On moving down the group, bond dissociation energy decreases and hence, E- H bond breaks easily.
(iii) Thus, the thermal stability of hydrides of group 16 elements decreases down the group. Hence the order of thermal stability is,
H₂O > H₂S > H₂Se > H₂Te > H₂Po

14.

(i) Both fluorine and oxygen have very high electron affinities and can easily cause the excitation of the electrons from 5p orbital to 5d orbital of xenon.
(ii) The unpaired electrons thus formed can take up electrons from oxygen or fluorine to form compounds.
(iii) Thus xenon has low ionisation energy and it can form compounds with strong oxidising agents (high E.A) like F₂ and O₂·

15.

(i) Its small size
(ii) Its high electronegativity
(iii) Its high ionisation energy
(iv) Non-availability of d-orbital in the valence shell.
(v) Rather inert
(vi) High bond energy

Assertion and reason

2 x 2 = 4

16.

a) Both assertion and reason are true and reason is the correct explanation of the assertion

17.

a) Both assertion and reason are true and reason is the correct explanation of the assertion

One or Two Words / Correct Statement

2 x 1 = 2

18.

()
II and III only

19.

()
I, III and IV only

Find the wrong statement

2 x 2 = 4

20.

XeO₃ - Bent T shape

21.

Metal nitrate is formed with the release of nitrogen.

Generic 5

2 x 5 = 10

22.

(i) As per the position in the periodic table, the element A is phosphorus as below:
(ii) Phosphorus reacts with dry chlorine to form phosphorus trichloride as below
\(\underset { (A) }{ { P }_{ 4 } } +6{ Cl }_{ 2 }\longrightarrow \underset { (B) }{ { 4PCl }_{ 3 } } \)
Hence, compound B is phosphorus trichloride.
(iii) PCl₃ on hydrolysis gives phosphorus acid H₃PO₃, which is dibasic acid,
\(\underset { (B) }{ { PCl }_{ 3 } } +3{ H }_{ 2 }O\longrightarrow { 3HCl }+\underset { (C) }{ { H }_{ 3 }{ PO }_{ 3 } } \)
Hence, compound C is phosphorus acid.
(iv) H₃PO₃ on heating undergo auto oxidation and reduction producing phosphoric acid md phosphine as below:
\(\underset { (c) }{ { 4H }_{ 3 }{ PO }_{ 3 } } \overset { \Delta }{ \longrightarrow } { PH }_{ 3 }+\underset { (b) }{ { 3H }_{ 3 }{ PO }_{ 4 } } \)
Phosphoric acid is a tribasic acid. Hence, compound D is phosphoric acid.
Thus A = Phosphorus
B = Phosphorus trichloride
C = Phosphorus acid
D = Phosphoric acid

23.

(i) Because of its lightness and noninflammability helium is used to filling balloons for meteorological observations.
(ii) Because of its lightness it is used in inflating aeroplane tyres.
(iii) Helium oxygen mixture is used by deep sea divers in preference to nitrogen oxygen mixtures. This prevents bends when a diver comes to the surface.
(iv) A mixture of oxygen and helium is used in the treatment of asthma.
(v) Liquid helium (b.pt 4.2K) is used as cryogenic agent for carrying out various experiments at low temperatures.
(vi)It is used to produce and sustain powerful super conducting magnets of modern NMR Spectrometers and Magnetic Resonance Imaging system (MRI) for clinical diagnosis.