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chemistry > P block - 15 and 16 > Flashcards

P block - 15 and 16 Flashcards

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1
Q

Which are the metals, non-metals and metalloids of group 15

A

Non-metals - Nitrogen, Phosphorous
Metalloids - Arsenic and Antimony
Metals - Bismuth and Moscovium

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2
Q

How is nitrogen found in the atmosphere

A

NaNO3 - Chile saltpetre
KNO3- Indian saltpetre
Proteins in plants and animals

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3
Q

Where are arsenic, antimony and bismuth found

A

sulphide minerals

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4
Q

Comment of the atomic and ionic radii of group 15

A

Increase down the group

Considerable increase from N to P due to presence of completely filled f and d block

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5
Q

Comment on the melting point of group 15

A

Increase upto Arsenic and then decrease

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6
Q

What are the anomalous properties of Nitrogen

A

forms pπ - pπ bonds with itself
Forms triple bond
High bond enthalpy
Catenation tendancy is weaker

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7
Q

What is the trend of stability of hydrides of group 15

A

decreases from NH3 to BiH3

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8
Q

What is the trend of reducing character of hydrides

A

Increases from NH3 to BiH3

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9
Q

Why does NH3 have higher boiling and melting point than PH3

A

H bonding in solid and liquid phase

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10
Q

What is trend of basicity in hydrides

A

NH3>PH3>AsH3>SbH3>BiH3

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11
Q

What type of oxides does group 15 form. Which is more acidic

A

E2O3 and E2O5. The oxide in higher oxidation state is more acidic. Acidic char decreases down the group.

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12
Q

Comment on covalency of halides of group 15

A

EX5 is more covalent than EX3. +5 has more polarising power. Covalency decreases down the group

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13
Q

How to prepare N2

A
  1. liquefaction and fractional distillation of air. Liquid N2 distils out first.
  2. In lab, NH4Cl + NaNO2. Small amounts of NO and HNO3 are formed which can be removed by passing gas through sulphuric acid containing potassium dichromate
  3. Very pure nitrogen obtained by thermal decomposition of sodium or barium azide
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14
Q

What is Habers process

A

N2 + 3H2 at 773K = 2NH3

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15
Q

How to form nitric oxide

A

N2 + O2 at around 2000K

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16
Q

How to prepare ammonia

A

In nature - decay of nitrogenous organic matter like urea
From ammonium salts which decompose on treatment with caustic soda or calcium hydroxide
On large scale by Haber’s process (N2 + H2)

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17
Q

What are the optimum conditions for prep of ammonia

A

high pressure (200atm) and temperature around 700K. Use of catalysts such as iron oxide with small amounts of K2O and Al2O3

18
Q

What is the structure of ammonia molecule

A

Trigonal pyramidal. 3bp and 1 lp

19
Q

How to prepare Nitric acid

A
  1. Heating KNO3 or NaNO3 and conc H2so4
  2. Ostwald’s process - catalytic oxidation of NH3 by atmospheric oxidation. No is formed which comines with oxygen to give NO2. NO2 dissolves in water to give HNO3
20
Q

What is structure of HNO3

A

planar molecule

21
Q

How does zinc react with HN3

A

dilute HNO3 to give Zn(NO3)2 + N2O

Conc HNO3 to give Zn(NO3)2 + NO2

22
Q

What is brown ring test

A

Fe2+ reduces nitrates to nitic oxide which reacts with Fe2+ to give a brown coloured complex

23
Q

What is group 16 also called

A

Chalcogens

24
Q

What is the trend of electron gain enthalpy of group 16

A

OSe>Te>Po . Because of compact nature of oxygen

25
Q

Why is there a large difference in melting and boiling points of S and O

A

Atomicity. O exists as O2 and S exists as S8

26
Q

What is the trend of thermal stability

A

decreases from H2O to H2Po

27
Q

What is the trend of reducing property of hydrides and oxides

A

hydrides increase from H2S to H2Te

oxides reducing property decreases from SO2 to TeO2

28
Q

What is the structure of hexaflourides

A

octahedral

29
Q

What is structure of tetraflourides

A

bipyramidal structure with see-saw geometry

30
Q

How to prepare dioxygen

A
  1. By heating oxygen containing salts
  2. By thermal decomposition of oxides of metals low in the electrochemical series
  3. H2O2 readily decomposes into water and O2 by catalysts such as finely divided metals and MnO2
  4. From air by fractional distillation
31
Q

Name some neutral oxides

A

CO, NO, N2O

32
Q

How to prepare ozone

A

slow dry stream of oxygen passed through silent electrical discharge

33
Q

What are colours of ozone

A

pale blue gas, dark blue liquid, violet black- solid

34
Q

What is a quantitative method for determining O3

A

ozone + excess KI soln buffered with borate buffer - iodine is liberated which can be titrated against standard solution of sodium thiosulphate

35
Q

How to form rhombic sulphur crystals

A

evaporating solution of roll sulphur in CS2

36
Q

How to prepare monoclinic sulphur

A

by melting rhombic sulphur

37
Q

What happens to monoclinic sulphur at 369 K

A

for beta - above it is stable and below it becomes alpha
for alpha below it is stable and above it becomes beta
at 369 both are stable

38
Q

How is SO2 prepared

A

sulphur burnt in air/O2
treating sulphite with dil sulphuric acid
roasting on sulphide ores

39
Q

How is sulphuric acid manufactured

A

Contact process:
1. burning of sulphur/ sulphide ored in air to generate SO2
2. conversion of So2 to So3 by reaction with oxygen in presence of catalyst (V2O5)
Absorption of SO3 in H@SO$ to give oleum
low temp high pressure
dilution of oleum with water gives H2SO4
96-98% pure

40
Q

How is sulphuric acid manufactured

A

Contact process:
1. burning of sulphur/ sulphide ore in air to generate SO2
2. conversion of So2 to So3 by reaction with oxygen in presence of catalyst (V2O5)
Absorption of SO3 in H@SO$ to give oleum
low temp high pressure
dilution of oleum with water gives H2SO4
96-98% pure

41
Q

What are the properties of sulphuric acid

A 
Strong dehydrating agent 
moderately strong oxidising agent 
low volatility
strong affinity for water 
strong acidic character

chemistry (3 decks)

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