s block (I group elements ) Flashcards
1
Q
Nature of oxysalts: Alkali metals readily react with oxyacids forming corresponding salts with evolution of hydrogenThe members of Group IA or 1, except hydrogen are called
A
alkali metals
2
Q
s block element react with water to form ______solutions
A
alkanline
3
Q
All the group 1A elements are _____metals(colour and hardness)
A
soft and slivery grey
4
Q
Their valence electron configurations are ____
A
ns1
5
Q
The group IA of the periodic table consists of six elements—
A
lithium, sodium, potassium, rubidium, caesium and francium besides hydrogen
6
Q
the hydroxides of these metals are soluble in____ and these solutions are ________ in nature.
A
the hydroxides of these metals are soluble in water highly alkaline in nature.
7
Q
The alkali metals are so reactive that, they must be stored under _____
A
oil or kerosene
8
Q
The silvery lustre of alkali metals is due to the presence of ______
A
highly mobile electrons of the metallic lattice.
9
Q
these metals are soft in nature because
A
the metallic bonding is not so strong.
10
Q
the softness increases with increase of atomic number because
A
because there is continuous decrease of metallic bond strength on account of an increase in atomic size
11
Q
Bigger is the size of metal kernel weaker is the ___
A
metallic bonding
12
Q
Group IA atoms are the _____ (compared size) acc to the periodic table
A
Group IA atoms are the largest in their horizontal periods in the periodic table
13
Q
When the outermost electron is removed to give a positive ion, the size decreases considerably. There are two reasons for this
A
: (i) The outermost shell of electron has been completely removed.
(ii) The positive charge on the nucleus is now acting on lesser number of electrons, i.e., attraction increases which brings contraction in size
14
Q
Atomic as well as ionic size increases from Li to Fr
A
due to the presence of one extra shell of electrons
15
Q
how is atomic volume and atomic no related
A
Atomic volume also increases as the atomic number increases
16
Q
density of s block
A
Density gradually increases in moving down from Li to Cs. Potassium is, however, lighter than sodium.
17
Q
The reason for the low values in density?
A
is that these metals have high atomic volumes. The abnormal value of potassium is due to unusual increase in atomic size, i.e., atomic volume.
18
Q
the metals have low melting and boiling points. These decrease in moving down from Li to Cs… why?
A
as the metallic bond strength decreases or cohesive force decreases.
19
Q
reasons for low Ionisation energies and electropositive character of s block
A
Due to their large size, the outermost electron is far from the nucleus and can easily be removed. Their ionisation energies or ionisation enthalpies are relatively low…. the metals have a great tendency to lose the ns' electron to change into M+ ions explains electro+ character
20
Q
As the ionisation enthalpy decreases from
A
li to cs
21
Q
from Li to Cs, the electropositive character (increases or decreases)
A
, the electropositive character increases, i.e., metallic character increases
22
Q
The reactivity of these metals increasesfrom
A
li to cs
23
Q
The ns1; electron is so loosely held that even the low energy photons (light) can eject this electron from the metal surface. This property is termed as
A
photoelectric effect
24
Q
___ and ___are used in photoelectric cells which are sensitive to blue light
A
K and Cs
25
The alkali metals can lose their ns1; electron quite easily to form univalent positive ion, M+
its just facts to remember ;)
26
the radii of the hydrated ion decreases from
li+ to cs+
27
he ionic conductance of these hydrated ions increases from .
[Li(aq.)] to [Cs(aq.)]*
27
Hydration of ions is an process
exothermic
28
explain hydration energy.
The energy released when one gram mole of an ion is dissolved in water to get it hydrated is called hydration energy.
29
reasons why alkali metals have high reactivity
(i)they have low ionization energies and are readily lose thier electrons to form M+
(ii)They have low heat of atomisation and easily come into vaporised form.
(iii) They have high heats of hydration
30
explain their Reactivity towards air
On exposure to moist air, all alkali metals except lithium tarnish quickly. The effect of atmosphere increases from Li to Cs. These are, therefore, always kept under kerosene to protect them from air.
31
Lithium when heated in air combines with _______ to form _________
Lithium when heated in air combines with nitrogen to form nitride
32
explain their Reactivity towards water:
Alkali metals decompose water with the evolution of hydrogen.Lithium decomposes water slowly. Sodium reacts with water quickly, K, Rb and Cs react with water vigorously. The decomposition is highly exothermic and the evolved hydrogen sometimes inflames. Thus, the reactivity towards water increases from Li to Cs. This is due to increase of electropositive character in the same order
33
The alkali metals also react with alcohols forming ______ with the evolution of hydrogen.
The alkali metals also react with alcohols forming alkoxides with the evolution of hydrogen. This reaction is used in preliminary test of alcoholic group
34
explain their Affinity for non-metals
Affinity for non-metals: Alkali metals have great affinity for non-metals
35
explain their Reactivity towards hydrogen:
The alkali metals combine directly with hydrogen to form crystalline hydrides of the formula MH. These hydrides are ionic and contain the hydride
36
The electrolysis of the fused hydride (LiH) yields hydrogen at anode [other hydrides decompose before melting.]
facts
37
The hydrides react with water liberating hydrogen
facts
38
The ionic character of the bonds in these hydrides increases from _____to_____ and their stability decreases in the same order. They are powerful reducing agents especially at high temperatures.
The ionic character of the bonds in these hydrides increases from LiH to CSH and their stability decreases in the same order. They are powerful reducing agents especially at high temperatures.
39
explain Reactivity towards oxygen (oxides and hydroxides):
Affinity towards oxygen increases. When heated in atmosphere of oxygen, the alkali metals ignite and form oxides. On combustion Li forms Li2O; sodium gives the peroxide, Na2O2 and potassium, rubidium and caesium give superoxides
40
The peroxides and superoxides become more stable with increase ________
The peroxides and superoxides become more stable with increase in atomic number of the alkali meta
41
explain The formation and stability of these oxides of s bolck
The formation and stability of these oxides can be explained on the basis of lattice energy effects. Li* ion being a small ion has a strong positive field around it and can stabilise only a small anion, O2 whereas Na* being a large cation can stabilise a large ion and so on.
42
The normal oxides react with water to form
hydroxides
43
The basic nature of the oxides (M2O) increases gradually on________in the group
The basic nature of the oxides (M2O) increases gradually on moving down in the group
44
explain hydroxides (MOH)
The hydroxides (MOH) are colourless, strong alkaline and corrosive compounds. These are soluble in water and dissolve with the evolution of heat. The hydroxides are thermally stable except LiOH!
45
The relative strength of the hydroxides increases from
LiOH to CSOH (CsOH >RbOH >KOH >NaOH LiOH)
46
The higher oxides, viz., peroxides and superoxides are strong ___agents. They react with dilute acids forming _____ respectively
The higher oxides, viz., peroxides and superoxides are strong oxidising agents. They react with dilute acids forming hydrogen peroxide and oxygen respectively
47
The peroxides are _____magnetic in nature (all the electrons are paired) and are regarded as the salts _______, .
The peroxides are diamagnetic in nature (all the electrons are paired) and are regarded as the salts of the dibasic acid, H2O2. The superoxides are paramagnetic and coloured as odd
48
the yellow color of na2o2 is due to
the presence of superoxides
48
explain Reactivity towards halogens
: The alkali metals directly react with halogens forming the halides of the type MX
49
The reactivity of alkali metals towards a particular halogen increases from
Li to Cs.
50
reactivity of halogens towards a particular alkali metal decreases from
F2 to I2 (F= fluoride and I= iodine )
51
With the exception of certain_______, the alkali metal halides are ionic compounds
lithium halides all the alkali metal halides are ionic compounds
52
The halides are_____ and have ___ melting and _____ points.
The halides are crystalline and have high melting and boiling points.
53
. The fused halides are_________ of electricity and are used for the preparation of
. The fused halides are good conductors of electricity and are used for the preparation of alkali metals.
54
All halides except dissolve in water.
All halides except LiF dissolve in water.
55
Alkali metal halides are colourless but on heating they turn ______
on heating they turn yellow, blue, etc.
56
Halides of potassium, rubidium and caesium have a property of combining with extra halogen atoms forming
polyhalides
57
explain the insolubity of LiF
The lithium ion has the highest energy of hydration as it is small in size in comparison to other alkali metal ions and thus it should have high solubility. However, the small Li* and F ions interact very strongly resulting in high lattice energy of LiF which is responsible for its insolubility (the ionic compounds, which possess low value of lattice energy, are freely soluble in water
58
reAction with sulphur and phosphorus.
Alkali metals directly combine with sulphur and phosphorus when heated with them.
59
explain reaction Nature of oxysalts
: Alkali metals readily react with oxyacids forming corresponding salts with evolution of hydrogen
60
why does Li salts behave soo abnormally
Lithium salts behave abnormally due to polarising power of Li* ion (small size) and lattice energy effects.
61
explain the stability of the carbonates
Since the alkali
metals are highly electropositive, their carbonates are highly
stable towards heat and readily soluble in water. As the
electropositive character increases from-Li to Cs, the stability of the carbonates increases in the same order.
62
______(carbonates)decomposes on heating and is insoluble in water
LICO3
63
The aqueous solutions of carbonates are alkaline why?
This is
due to hydrolysis as carbonates are salts of strong bases and
weak acid (H2C03 carbonic acid)
64
The bicarbonates, MHC03, of the alkali metals, with the
exception of____ are known in solid state
lithium,
65
The bicarbonates
are soluble in water. On heating, bicarbonates decompose into
carbonates with evolution of C02
facts
66
The abnormal behaviour of Li2C03 towards heat can be
explained in the following manner
The Li+ ion exerts a strong polarising action and distorts the electron cloud of the nearby oxygen atom of the large CO§-
ion. This results in the weakening of the C-O bond and strengthening of the Li--O bond. This ultimately facilitates the decomposition of Li2C03 into Li20 and C02. The lattice energy of Li20 is higher than the lattice energy of carbonate
67
Lithium due to its less electropositive nature, does not form
solid bicarbonate
facts
68
Nature of nitrates explain
Nature of nitrates: These are colourless, soluble in water and electrovalent
in nature. The nitrates do not undergo hydrolysis. With the exception ofLiN0
69
what if LINO3 is heated
Lithium nitrate decompose to oxide on heating, it is due to
diagonal relationship with magnesium., the other nitrates decompose to nitrites and oxygen.
70
With the exception____, other sulphates are
soluble in water
LiSO4
71
formula potash alum
, K2S04·AI2(S04h·24H20
72
explain the Nature of perchlorates:
: Perchlorates of the type
MCl04 are known. The stability increases gradually as larger
M+ ion form more stable lattice with large CI04 ion. The
solubility of perchlorates decreases.
LiCI04 > NaCl04 > KCI04 > RbCI04 > CSCI04
73
explain the SOlubility iniiqUid ammonia
:· The -alkali metals dissolve in liquid ammonia without the evolution of hydrogen. The colour of the dilute solutions is blue. The metal atom loses electron and it combines with ammonia molecule.On heating its blue colour changes to bronze.
It is ammoniated electron which is responsible for colour. The solutions are good conductors of electricity and have strong reducing properties. The solutions are paramagnetic in nature.
74
When dry ammonia is passed over hot metal, _______ are
formed.
amides are
formed.
75
Complex formation among alkali metals .
Alkali metals have a very little
tendency to form complexes. Lithium being small in size forms
certain complexes but this tendency decreases as the size
increase
76
failure in Extraction of alkali metals:
(i) Alkali metals are strong reducing agents, hence cannot be extracted by reduction of their oxides and other compounds.
(ii) Being highly electropositive in nature, it is not possible to apply the method of displacing them from their salt solutions
by any other element.
(iii) The aqueous solutions of their salts cannot be used for extraction by electrolytic method because hydrogen is discharged
at cathode instead of an alkali metal as the discharge potentials of alkali metals are high. However, by using Hg as cathode, alkali metal can be deposited. The alkali metal readily combines with Hg to form an amalgam from which its recovery is very difficult
77
successful methods extraction of alkali metals
The only successful method, therefore, is the electrolysis of their fused salts, usuaJly chlorides. Generally, another metal chloride is' added to lower its fusion temperature.
78
Reasons for its abnormal behaviour are mainly due to the what
reasons:
(i) Lithium atom and its ion has very small size. Lithium ion (Li+) on account of its small size exerts high polarising effect on anions in its compounds resulting in increased covalent character
(ii) Lithium atom has highest ionisation enthalpy and low electropositive character as compared to other alkali metals
(iii) Nonavailability of d-orbitals in its valence shell.
(iv) Lithium has strong metallic bonding which is responsible for its low reactivity to some extent
79
Lithium differs from alkali metals in the what respects:
(i) It is more harder and lighter than other alkali metals.
(ii) It is not affected by air easily and does not lose its lustre even on melting.
(iii) It reacts slowly with water to liberate hydrogen
(iv)When burnt in air or oxygen, it forms only monoxide, Li20. However, the
rest of the alkali metals give peroxides or superoxides
(v) Lithium is the only alkali metal which directly reacts with nitrogen to form Li3N.
(vi) Lithium hydroxide decomposes at red heat to form Li20. Hydroxides of other alkali metals donot decompose.
(vii) Lithium bicarbonate,is not in solid state while the bicarbonates of other alkali metals are known in solid state.
(viii)Li2C03 is less stable, as it decomposes on heating.The other carbonates are stable
(ix) LiN03, on heating gives a mixture of N02 and 02 while nitrates of rest of alkali metals yield only oxygen,
(x) Li2S04 is the only alkali metal sulphate which does n0t form double salts, e.g., alums.
(xiii) LiCl is highly deliquescent and soluble in alcohol and pyridine. LiCI separates out from aqueous solution as hydrated
crystals LiCI·2H20 whereas chlorides of other alkali metals are insoluble in organic solvents and do not form hydrated crystals
under ordinary temperatures.
(xiv) Li when heated in NH3 forms imide Li2NH while other alkali metals form amides, MNH2.
(xv) LiOH is much weaker base than NaOH or KOH
79
Reasons for the diagonal relationship between li and mg are?
(i) Electronegativities of Li and Mg are quite comparable .(ii) Atomic radii and ionic radii of Li and Mg are not very much different.
(iii) Atomic volumes of Li arid Mg are quite similar.
(iv) Both have high polarising power (ionic potential)
80
Lithium resembles magnesium in the what
respect
(a) Both Li and Mg are harder and have higher melting points than the other metals in their respective groups
(b)Li like Mg decomposes water slowly to liberate hydrogen
(c) Both the elements combine with nitrogen on heating.Both the nitrides are decomposed by water with evolution
of ammonia (NH3).
(d) Both Li and Mg combine with carbon on heating.
(e) both forms only monoxide when heated in oxygenBoth the oxides are less soluble in water
(f) Hydroxides ofLi and Mg are weak bases and are slightly soluble in water. Both decompose on heating.
Alkyls of Li and Mg are soluble in organic solvents
81
Important minerals of lithium are:
Aluminosilicates -Lepidolite or lithiamica
Phosphate- triphylite
82
The extraction of lithium involves two steps: which are
(i) Preparation of lithium chloride from the mineral.
(ii) Electrolysis of lithium chloride
83
LiCI is extracted from the solid residue with the help of ________
pyridine
84
e. From the pyridine solution, LiCI is recovered by_____ process
by distillation.
85
Lithium is obtained by the electrolysis of a fused mixture of _______ and ______ in equal amounts
lithium chloride and potassium chloride in equal amounts
86
why is it imp for the addition of potassium chloride during electrolysis of licl
(i) It increases the conductivity of the fused mass.
(ii) It lowers the fusion temperature of lithium chloride
87
Reactivity towards alkalies
on lithium.
Alkalies have no action on lithium.
88
uses of lithium
(i)In the refining of metals (the purification. of nickel and copper)
(ii)In the preparation ,Of useful alloys(It increases tensile strength and resistance to corrosion)
(iv)Thermonuclear purposes(when bombarded with neutrons, it produces tritium.)
(v) Lithium batteries
Lithium alkyls/aryls are used in the preparation of organometallic compounds
89
Sodium is obtained on large scale by two processes namely
(i) Castner's process
(ii) Down's process
90
explain Castner's process
In this process, electrolysis
of fused sodium hydroxide is carried out at 330C using iron as cathode and nickel as anode. During electrolysis, oxygen and water are produced. Water formed at the anode gets partly evaporate and is partly broken down and hydrogen is discharged at cathode
91
explain downs process
It involves the electrolysis of fused . sodium chloride containing calcium chloride and potassium fluoride using iron as cathode and graphite as anode at about 600C, the melting point of the mixture
92
how is Sodium Oxide Na2O produced
It is prepared by heating sodium nitrate or
sodium nitrite with sodium or Pure sodium oxide is formed when the mixture of sodium azide and sodium nitrite is heated
93
how is sodium peroxide formed?
It is formed by heating sodium in excess
of air free from moisture and carbon dioxide or in excess of
pure oxygen.It is a pale yellow powder.
94
how is Sodium Hydroxide formed
(i) Casuticisation process (Gossage process)
(ii) Lowig's process
95
explain causticisation process (Gossage process)
This process depends on the reaction between suspension ·of lime
(milk of lime, calcium hydroxide) and sodium carbonate
96
explain lowig progess
Lowig's process: In this process, a mixture of sodium carbonate and ferric oxide is heated to redness in a revolving furnace. Sodium ferrite is thus formed with evolution
of carbon dioxide.
97
on passing electricity through NaCl solution what is formed at cathode and anode
cathode :- H2 gas
anode :- Cl2 gas
98
the three main processes for the manufacture of sodium carbonate :
(a) Le-Blanc process,
(b) Solvay ammonia soda process and
(c) Electrolytic process.
99
explain le blanc process
(i) Conversion of NaCI into Na2S04
(NaHS04 + NaCI = Na2S04 + HCI)
(ii) Conversion of salt cake into black ash
(Na2S04 + CaC03 + 4C=7 Na2C03 + CaS + 4CO)
(iii) Recovery of Na2C03
100
explain Solvay ammonia soda process
The raw materials required in this
process are the common salt, ammonia and limestone. In the main steps of this process, ammonia is 1st dissolved in a saturated solution of sodium chloride and then carbon dioxide is passed in it. The process involves the formation of a sparingly
soluble sodium bicarbonate Sodium bicarbonate on heating decomposes into sodium carbonate
101
soda ash formula
Na2C03
102
sodium carbonate Reaction with acids
: It is readily decomposed by acids with evolution of carbon dioxide.
103
sodium carbonate Reaction with C02
: On passing CO2 through the
concentrated solution of sodium carbonate, sodium bicarbonate
gets precipitated.
104
sodium carbonate Reaction with silica
: When the mixture of sodium
carbonate and silica is fused, sodium silicate is formed.Sodium silicate is called soluble glass or water glass as it
is soluble in water
105
sodium carbonate Reaction with slaked lime.
: Sodium hydroxide
is formed when the solution of sodium carbonate and slaked
lime, Ca(OHh, is heated
106
sodium carbonates Reaction with sulphur and sulphur dioxide:
When aqueous solution of. sodium carbonate containing sulphur is
treated with sulphur dioxide, sodium thiosulphate (Na2S203)
is formed
107
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109
110
111
112
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