Flashcards
Alkali Metals
Cards in this deck (25)
- 1Group 1 Alkali MetalsConsists of Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb) Caesium (Cs) and Francium (Fr) (radioactive)
General config- ns1 - 2Physical Propertiessoft in nature and can be cut with knife except lithium
Alkali metals have the largest atoms in their respective periods
melting and boiling points are very low because of weak inter metallic bonds - 3Physical Properties (contd...)first ionization enthalpy of the alkali metals are the lowest as compared to other elements
show +1 oxidation state
strong tendency to lose electrons and act as good reducing agents
Less reduction potential - 4Physical Properties (contd...)alkali metals form ionic (electrovalent) compounds
alkali metals are good conductors of heat and electricity
Alkali metals (except Li) exhibit photoelectric effect
alkali metals and their salts impart a characteristic colour to flame - 5Flame TestLi - Crimson Red
Na - Golden Yellow
K - Pale Violet
Rb - Violet
Cs - Sky Blue - 6Chemical Properties With Wateralkali metals, their oxides, peroxides and superoxides readily dissolve in water to produce corresponding hydroxides which are strong alkalies
- 7Chemical Properties With Water (cont...)2Na + 2H2O → 2NaOH + H2
Na2O + 2H2O 2NaOH
Na2O2 + 2H2O → 2NaOH + H2O2
2KO2 + 2H2O → 2KOH + H2O2 + O2 - 8Chemical Properties With Water (cont...)strength of these hydroxides increases as we move down the group Li to Cs
these hydroxides are highly soluble in water and thermally stable except lithium hydroxide
Alkali metal hydroxides are strongly basic and react with all acids forming salts - 9Reaction with AcidsAlkali metal hydroxides are strongly basic and react with all acids forming salts & water
NaOH + HCI → NacI + H2O
2NaOH + H2 SO4 → Na2SO4 + 2H2O - 10Reaction with HalogensM2O + 2HX → 2MX + H2O
MOH + HX → MX + H2O
M2CO3 + 2HX → 2MX + CO2 + H2O
(M is the metal = Li, Na, K, Rb or Cs)
(X is the halogen = F, Cl, Br or I) - 11Ionization EnthalpyIncreases as we go from left to right in a period and from top to bottom in a group!
- 12Lattice Energya measure of the energy contained in the crystal lattice of a compound, equal to the energy that would be released if the component ions were brought together from infinity-
Noticed in alkali metal halides
Lattice energy reduces across the group as the radius increases and it increases across the period as the atomic radius decreases - 13Hydration Energy1.Amount of energy released when one mole of gaseous ions combine with water to form hydrated ions
2. Li halides have the highest hydration energy and is soluble in water.
3. Solubility of alkali halides decreases down the group - 14Anomalous behavior of Li1. Li reacts with Oxygen to form oxide and the rest form peroxides or superoxides
2. Lithium Nitrates gives Lithium Oxide or decomposing. Remaining give respective nitrites
3. LiCI2H2O. & MgCI2.8H2O are deliquescent and crystallize as hydrate, Other alkali metals do not form hydrates. - 15Diagonal relationship between Li and Mg1. Both have same polarizing power
2. Both are hard
3. Both Hydroxides are basic in nature
3. due to their covalent nature, their halides are soluble in organic solvents
4. Reacts with Nitrogen to form Nitride
5. Both form hydrates - 16Diagonal relationship between Li and Mg6. Both readily react with Carbon and form Carbides
7. Carbonates, Hydrides and Nitrates of both Li & Mg decompose on heating
8. Hydrogen carbonates of both Li and Mg cannot be isolated in solid state - 17Sodium Hydroxide (NaOH) Properties1. Is stable when heated
2. When heated with Carbon, it is reduced and gives Hydrogen
2NaOH + 2C → 2Na +2CO + H2 - 18Uses1. It is used in the manufacture of paper, soap and artificial silk
2. in petroleum refining
3. for mercerizing cotton.
4. for the preparation of sodium metal and many salts of sodium. - 19Sodium Carbonate (Washing soda) (Na2CO3)Prepared through Solvay process: Carbon dioxide gas is bubbled through a brine solution saturated with ammonia and itresults in the formation of sodium hydrogen carbonate
- 20Sodium Carbonate (Washing soda) (Na2CO3)NH3 + H2O + CO2 → NH4HCO3
NaCI + NH4HCO3 → NaHCO3 + NH4CI
Sodium hydrogen carbonate so formed precipitates out because of the common ion effect caused due to the presence of excess of NaCl. The precipitated NaHCO3 is filtered off and then ignited to get Na2CO3.
2NaHCO3 → Na2CO3 + CO2 + H2O - 21Properties - NaHCO3The aqueous solution absorbs CO2 yielding sparingly soluble sodium bicarbonate.
Na2CO3 + H2O + CO2 → 2NaHCO3 - 22Properties - NaHCO3dissolves in acids with an effervescence of carbondioxide and is causticised by lime to give caustic soda.
Na2CO3 + 2HCl →2NaCl + H2O + CO2
Na2CO3 + Ca(OH)2 → 2NaOH + CaCO3 - 23Properties - NaHCO3Fusion with silica, sodium carbonate yields sodium silicate.
Na2CO3 + SiO2 → Na2SiO3 + CO2 - 24Properties - NaHCO3Hydrolysis – being a salt of a strong base (NaOH) and weak acid (H2CO3), when dissolved in water sodium carbonate. Undergoes hydrolysis to form an alkaline solution
Na2CO3 + 2H2O→ H2CO3 + 2NaOH - 25Uses - NaHCO31. used for softening hard water.
2. A mixture of sodium carbonate & potassium carbonate is used as fusion mixture.
3. As an important laboratory reagent both in qualitative and quantitative analyses.
4. used in paper, paints and textile industries.
5. for washing purposes in laundry.
6. in the manufacture of glass, borax, soap and caustic soda.
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- These slides give you an overview and understanding some basic characteristics of alkali metals
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- Kiranmayi Bapi
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