P Block 8 Flashcards
1
Q
NH3(excess) with Cl2 forms
A
2
Q
heating Pb (NO3)2 forms
A
3
Q
Cl2 with Hot conc NaOH forms
A
4
Q
Conc HNO3 with I2
A
5
Q
A
In the earth’s crust, it occurs as sodium nitrate, NaNO3
(called Chile
saltpetre) and potassium nitrate (Indian saltpetre).
6
Q
A
Ca9 (PO4
)6
. CaF2
) which are the main components of phosphate rocks
7
Q
A
Arsenic, antimony and bismuth are found mainly as
sulphide minerals
8
Q
A
The only well characterised
Bi (V) compound is BiF5
.
9
Q
A
3HNO2 → HNO3
+ H2O + 2NO
10
Q
A
N–N bond is weaker than the single P–P bond because of high
interelectronic repulsion of the non-bonding electrons, owing to the
small bond length
11
Q
A
As a result the catenation tendency is weaker in nitrogen.
12
Q
A
BiH3 is the
strongest reducing agent amongst all the hydrides
13
Q
A
Their acidic character decreases down the group.
14
Q
A
In case of nitrogen, only NF3 is known to be stable.
15
Q
A
State will have more polarsing power than in +3 oxidation state. the covalent character of bonds is more in pentahalides.
16
Q
A
synthetic radioactive element
17
Q
A
Due to high electronegativity and small size of nitrogen
18
Q
A
NH3 exhibits hydrogen bonding in solid as well as liquid state.
19
Q
A
these impurities can be removed by passing the gas through aqueous
sulphuric acid containing potassium dichromate
20
Q
A
high pressure would
favour the formation of ammonia
21
Q
A
Earlier, iron was used as a catalyst with
molybdenum as a promoter
22
Q
A
In the laboratory, nitric acid is prepared by heating KNO3
or NaNO3
and concentrated H2SO4
in a glass retort.
23
Q
A
On a large scale it is prepared mainly by Ostwald’s process.
24
Q
A
NO thus formed is recycled and the aqueous HNO3
can be
concentrated by distillation upto ~ 68% by mass. Further
concentration to 98% can be achieved by dehydration with
concentrated H2SO4
25
Concentrated nitric acid is a strong oxidising agent and attacks
most metals except noble metals such as gold and platinum.
26
adding dilute ferrous sulphate solution to an aqueous solution
containing nitrate ion, and then carefully adding concentrated sulphuric
acid along the sides of the test tube. A brown ring at the interface
between the solution and sulphuric acid layers indicates the presence
of nitrate ion in solution.
27
A brown ring at the interface
between the solution and sulphuric acid layers indicates the presence
of nitrate ion in solution.
28
more reactive than
the other solid phases under normal conditions because of angular
strain in the P4
molecule where the angles are only 60°
29
It readily
| catches fire in air to give dense white fumes of P4O10.
30
Red phosphorus possesses iron grey lustre
31
In the laboratory, it is prepared by heating white phosphorus with
concentrated NaOH solution in an inert atmosphere of CO2
.
32
When pure, it is non inflammable but becomes inflammable owing
to the presence of P2H4 or P4 vapours
32
When pure, it is non inflammable but becomes inflammable owing
to the presence of P2H4 or P4 vapours
33
To purify it from the impurities it is absorbed in HI to form phosphonium iodide (PH4I) which on treating
with KOH gives off phosphine.
PH4I + KOH---> KI+ H2O+ PH3
34
The solution of PH3 in water decomposes
| in presence of light giving red phosphorus and H2.
35
Phosphine is weakly basic and like ammonia, gives phosphonium
compounds with acids e.g.,
36
Thionyl chloride with white phosphorus.
| P4+ 8SOCl2--> 4PCl2+ 4SO2 +2S2Cl
37
It reacts with organic compounds containing –OH group such as
CH3COOH, C2H5OH.
38
It reacts with organic compounds containing –OH group converting
them to chloro derivatives.
C2H5 OH + PCl5--> C2H5Cl+ POCl3+ HCl
CH3COOH+ PCl5--> CH3COCl+ POCl3 +HCl
39
two axial bonds are longer than equatorial bonds.
40
This is due to the fact that
the axial bond pairs suffer more repulsion as compared
to equatorial bond pairs
41
These acids in +3 oxidation
state of phosphorus tend to disproportionate to higher and lower
oxidation states.
42
These P–H bonds are not ionisable to give H+
and do not play any
role in basicity. Only those H atoms which are attached with oxygen in
P–OH form are ionisable and cause the basicity.
43
Thus, H3PO3 and H3PO4 are dibasic and tribasic, respectively as the structure of H3PO3
has two P–OH bonds and H3PO4 three.
44
forms about 46.6% by mass of earth’s crust. Dry air contains 20.946%
oxygen by volume.
45
Traces of sulphur occur as hydrogen sulphide in volcanoes. Organic
46
materials such as eggs, proteins, garlic, onion, mustard, hair and wool
contain sulphur.
47
Polonium occurs in nature as a decay
| product of thorium and uranium minerals.
48
Because of the compact nature of oxygen atom, it has less negative
electron gain enthalpy than sulphur
49
increase in acidic character can be explained
in terms of decrease in bond enthalpy for the dissociation of H–E
bond down the group.
50
Owing to the decrease in enthalpy for the
dissociation of H–E bond down the group, the thermal stability of
hydrides also decreases from H2O to H2Po.
51
The stability of the halides
decreases in the order F– > Cl– > Br– > I–
.
52
The well known monohalides are dimeric in nature.
53
Examples are S2F2+, S2Cl2, S2Br2, Se2Cl2 and Se2Br2
54
These dimeric halides undergo
disproportionation as given below
2Se2Cl2 → SeCl4 + 3Se
55
Dioxygen can be obtained in the laboratory by the following ways:
56
On large scale it can be prepared from water or air. Electrolysis of
water leads to the release of hydrogen at the cathode and oxygen
at the anode.
57
Industrially, dioxygen is obtained from air by first removing carbon
dioxide and water vapour and then, the remaining gases are liquefied
and fractionally distilled to give dinitrogen and dioxygen.
58
oxygen is used in oxyacetylene welding,
59
some metals in high oxidation state also have acidic character (e.g.,
Mn2O, CrO3, V2O5).
60
are CO, NO and N2O
61
When a slow dry stream of oxygen is passed through a silent electrical
discharge, conversion of oxygen to ozone (10%) occurs. The product is
known as ozonised oxygen.
62
Since the formation of ozone from oxygen is an endothermic process,
it is necessary to use a silent electrical discharge in its preparation to
prevent its decomposition
63
If concentrations of ozone greater than 10 per cent are required, a
battery of ozonisers can be used, and pure ozone (b.p. 101.1K) can be
condensed in a vessel surrounded by liquid oxygen.
64
if the concentration rises above about 100 parts per million,
breathing becomes uncomfortable resulting in headache and nausea.
65
Due to the ease with which it liberates atoms of nascent oxygen
(O3 → O2 + O), it acts as a powerful oxidising agent. For example, it
oxidises lead sulphide to lead sulphate and iodide ions to iodine.
PbS(s) + 4O3(g) → PbSO4(s) + 4O2(g)
2I–(aq) + H2O(l) + O3(g) → 2OH–(aq) + I2(s) + O2(g)
66
When ozone reacts with an excess of potassium iodide solution
buffered with a borate buffer (pH 9.2), iodine is liberated which can be
titrated against a standard solution of sodium thiosulphate. This is a
quantitative method for estimating O3 gas.
67
nitrogen oxides (particularly nitric
oxide) combine very rapidly with ozone and there is, thus, the possibility
that nitrogen oxides emitted from the exhaust systems of supersonic
jet aeroplanes might be slowly depleting the concentration of the ozone layer in the upper atmosphere.
68
NO (g) +O3(g)--> NO2(g)+ O2( g)
69
the molecule is angular
| as expected with a bond angle of about 117o
70
: It is used as a germicide, disinfectant and for sterilising water. It is also
used for bleaching oils, ivory, flour, starch, etc. It acts as an oxidising agent
in the manufacture of potassium permanganate.
71
It is insoluble in water but dissolves to some
| extent in benzene, alcohol and ether. It is readily soluble in CS2.
72
Monoclinic sulphur (β-sulphur)
Its m.p. is 393 K and specific gravity 1.98. It is soluble in CS2
. This form of sulphur is prepared by melting rhombic sulphur in a dish
and cooling, till crust is formed. Two holes are made in the crust and
the remaining liquid poured out. On removing the crust, colourless
needle shaped crystals of β-sulphur are formed
73
α-sulphur is stable below 369 K and transforms into β-sulphur above this.
74
At 369 K both the forms are stable
75
Both rhombic and monoclinic sulphur have S8 molecules
76
At elevated temperatures
(~1000 K), S2 is the dominant
species and is paramagnetic like O2
.
77
In the laboratory it is readily generated by treating a sulphite with
dilute sulphuric acid.
78
Industrially, it is produced as a by-product of the roasting of
sulphide ores.
79
Sulphur dioxide, when passed through water, forms a solution of
sulphurous acid.
80
Sulphur dioxide reacts with chlorine in the presence of charcoal (which acts as a catalyst) to give sulphuryl chloride, SO2Cl2
.
81
When moist, sulphur dioxide behaves as a reducing agent
2Fe3++ SO2+ 2H2O--> 2Fe2+ SO2-4+ 4H+
5SO2+2MnO-4+ 2H2O--> 5SO2-4+ 4H++ 2Mn2+
82
Sulphur dioxide is used (i) in refining petroleum and sugar (ii) in bleaching
wool and silk and (iii) as an anti-chlor, disinfectant and preservative. Sulphuric
acid, sodium hydrogen sulphite and calcium hydrogen sulphite (industrial
chemicals) are manufactured from sulphur dioxide. Liquid SO2
is used as a
solvent to dissolve a number of organic and inorganic chemicals.
83
Sulphuric acid is manufactured by the Contact Process which involves
three steps:
84
The SO2 produced is purified by removing dust and other
| impurities such as arsenic compounds.
85
The key step in the manufacture of H2SO4 is the catalytic oxidation
of SO2 with O2 to give SO3
in the presence of V2O5 (catalyst).
86
The reaction is exothermic, reversible and the forward reaction leads
to a decrease in volume. Therefore, low temperature and high pressure are the favourable conditions for maximum yield
87
The SO3 gas from the catalytic converter is absorbed in concentrated H2SO4 to produce oleum
88
In the industry two steps are carried out simultaneously to make the process a continuous one and also to reduce the cost
89
is 96-98% pure.
90
(a) low volatility (b) strong acidic character
| (c) strong affinity for water and (d) ability to act as an oxidising agent.
91
In aqueous solution, sulphuric acid ionises in two steps
H2SO4(aq) + H2O(l) → H3O+(aq) + HSO4–(aq); Ka1 = very large (Ka1>10)
HSO4–(aq) + H2O(l) → H3O+(aq) + SO42-(aq) ; Ka2 = 1.2 × 10–2
92
two series of salts: normal sulphates (such as sodium
sulphate and copper sulphate) and acid sulphates (e.g., sodium
hydrogen sulphate).
93
Sulphuric acid, because of its low volatility can be used to
| manufacture more volatile acids from their corresponding salts.
94
wet gases can be dried by passing them through sulphuric acid,
provided the gases do not react with the acid.
95
it is evident by its charring action on
| carbohydrates.
96
Other uses are in:
(a) petroleum refining (b) manufacture of pigments, paints and dyestuff
intermediates (c) detergent industry (d) metallurgical applications (e.g.,
cleansing metals before enameling, electroplating and galvanising
(e) storage batteries (f) in the manufacture of nitrocellulose products
and (g) as a laboratory reagent.
97
Astatine is a radioactive element.
98
the deposits of dried up seas
contain these compounds, e.g., sodium chloride and carnallite,
KCl.MgCl2.6H2O
99
marine life contain iodine in their systems; various seaweeds
100
Chile saltpetre contains upto 0.2% of sodium iodate.
101
Bromine and iodine are only sparingly soluble in water but are soluble in various organic solvents such as chloroform, carbon tetrachloride, carbon disulphide and hydrocarbons to give coloured solutions.
102
A reason for this anomaly is the relatively
large electron-electron repulsion among the lone pairs in F2 molecule
where they are much closer to each other than in case of Cl2
.
103
The reactivity of the halogens decreases
| down the group.
104
The ready acceptance of an electron is the reason for the strong
oxidising nature of halogens.
105
Fluorine oxidises water to oxygen whereas
| chlorine and bromine react with water to form corresponding hydrohalic and hypohalous acids.
106
The reaction of iodine with water is nonspontaneous.
107
I– can be oxidised by oxygen in acidic medium;
108
Hydrogen fluoride is a liquid (b.p. 293 K) due to strong hydrogen bonding.
109
Other hydrogen halides which have bigger size and less electronegativity are gases.
110
Hydrogen halides dissolve in water to form hydrohalic
| acids.
111
The acidic strength of these acids varies in the order:
| HF < HCl < HBr < HI
112
A combination of kinetic
and thermodynamic factors lead to the generally decreasing order of
stability of oxides formed by halogens, I > Cl > Br
113
Higher stability of oxides of iodine is due to greater polarisability of bond between iodine and oxygen
114
The higher oxides
| of halogens tend to be more stable than the lower ones.
115
in the case of chlorine. multiple bond formation between chlorine and oxygen takes place due to availability of d-orbitals. this leads to increase in stability.
116
Whats LCAO
it means the linear combination of two orbitals! the interference can happen in two ways! if it's constructive interference! it forms a bonding molecular orbital and if it's destructive then it forms anti bonding molecular orbital
117
Bromine Lacks both the characteristics hence stability of oxides of Bromine is least.
118
I2O5 is a very good oxidising agent and is
| used in the estimation of carbon monoxide
119
The ionic character of the halides decreases in the order MF >
MCl > MBr > MI
120
the halides in higher oxidation
| state will be more covalent than the one in lower oxidation state.
121
Deacon’s process: By oxidation of hydrogen chloride gas by
atmospheric oxygen in the presence of CuCl2
(catalyst) at 723 K
122
It bleaches vegetable or organic matter in the presence of moisture. Bleaching effect of chlorine is permanent.
123
fluorine forms only one
| oxoacid, HOF known as fluoric (I) acid or hypofluorous acid.
124
They are stable only in aqueous solutions or in the form of
| their salts.
125
```
In general, interhalogen compounds are more reactive
than halogens (except fluorine).
```
126
This is because X–X′ bond in
interhalogens is weaker than X–X bond in halogens except F–F
bond.
127
a red compound which is formulated as O2+PtF6–
| .
128
preparing another red colour compound Xe+PtF6– by mixing PtF6 and xenon.
129
difluoride (KrF2) has been studied in detail.
130
but only identified (e.g., RnF2) by radiotracer technique.
131
Ar, Ne or He are yet known
132
XeF2, XeF4 and XeF6 are colourless crystalline solids and sublime
readily at 298 K.
133
They are powerful fluorinating agents.
134
It is also used in gas-cooled nuclear reactors. Liquid helium (b.p. 4.2 K) finds use as cryogenic agent for carrying out
various experiments at low temperatures.
135
It is used to produce and sustain powerful superconducting magnets which form an essential part of modern NMR
spectrometers and Magnetic Resonance Imaging (MRI) systems for clinical diagnosis.
136
It is used as a diluent for oxygen in modern diving apparatus because
of its very low solubility in blood.
137
Argon is used mainly to provide an inert atmosphere in high temperature metallurgical processes (arc welding of metals or alloys) and for filling electric bulbs.
