METAL And Chemical Properties of metals
METAL
Metal is a element that has
metallic bond and have positive ions or cations. Metal is a lattice of positive
ions that are surrounded by the cloud of the electrons.
In the pure state, metal have a shining surface. This properties
are called metallic luster.
Here, metals are generally hard.
Metals are malleable, because they can be hammered into
thin sheets. This property is called as malleability.
Metals are ductile it means they can be drawn into wires.
The ability of the metals to be drawn into thin wires is called as ductility.
For example:-- gold is most
ductile metal.
Due to the properties of the ductility and malleability,
metals can be given in different shapes as per their needs.
Metals are opaque
Metals are lustrous elements that are good conductor of
heat and electricity.
Metals are denser than the other substances.
Metals are good conductor of heat. For example :-- silver
and copper. Lead and mercury are poor conductors of heat.
Metals have high melting point.
Chemical Properties of metals
Metals burns in Air
When the metals combine with oxygen , then it forms metal
oxides.
Metal + Oxygen → Metal oxide
Such as :-- when copper is heated in the presence of air
then it combines with Oxygen to form copper Oxide or black oxide.
2Cu + O2 → 2CuO
When aluminium is
heated with air then it forms aluminium Oxide
4Al + 3O2 → 2Al2O3
Reaction of hydrochloric acid with metal oxide
As we know that metal oxide are basic in nature.
Some of the metal oxides like aluminium oxide and zinc
oxide both are acidic or basic in nature.
Metal oxides which react with both acids as well as bases
to produce salts and water are called as atmospheric oxides.
Al2O3 + 6HCl → 2AlCl3 + 3H2O
Al2O3 + 2NaOH → 2NaAlO2 + H2O
Metal Oxides are insoluble in water. But some metal oxides reacts
with water to form alkalis.
For example:-- Sodium oxide dissolve in water to form
alkali
Na2O (s) + H2O (I) → 2NaOH (aq)
and potassium oxide dissolve
in water to form alkali
K2O (s) + H2O (I) → 2KOH (aq)
Why potassium and sodium kept immersed in the
kerosene oil?
Some of the metal like potassium and sodium are react so
vigorously that they catch fire if they kept in the presence of the air. To
protect and to prevent from the fire, they are kept immersed in to the kerosene
oil.
Why magnesium, aluminium, zinc lead etc are
kept cover with a thin layer of oxide?
At the ordinary temperature, the surfaces of metals such as
magnesium, aluminium, zinc lead etc are covered with the thin layer of oxide.
These protective oxide layers prevent the metal from oxidation.
Anodising:--
Anodising
is the process of forming a thick oxide layer of aluminium.
When aluminium exposed to the air , then aluminium develops
a thin oxide layer.
This aluminium oxide coat makes it resistance to further
corrosion. When the aluminium oxide layer get thicker, then the resistance can
be improved. During anodising, the aluminium article acts as the anode and is
electrolysed with dilute sulphuric acid. The oxygen gas are released from the
electrolyte to combine with the atom at the surface of the part being anodised.
Hence, a thicker protective oxide layer is made. Anodising is a process of highly controlled
oxidation. this oxide layer can be dyed to provide aluminium articles an
attractive finish.
When metals react with water
Metal oxide react with the water to produce a metal oxide
and hydrogen gas.
Metal + Water
Metal Oxide + Hydrogen
Metal Oxides are soluble in water. Metal oxide reacts with
water to form Metal hydroxide.
Meta Oxide + Water
Metal hydroxide
2K (s) + 2H2O (I) → 2KOH (aq) + H2 (g) + heat energy
2Na (s) + 2H2O (I) → 2NaOH (aq) + H2 (g) + heat energy
Here, in the case of the potassium (K) and sodium
(Na), the reaction is so violent and
exothermic. The evolved hydrogen gas catches fire immediately.
Here, magnesium dose not react with cold water. Magnesium
react with hot water to form magnesium hydroxide and hydrogen gas. The reaction
of the magnesium with water is less violent.
Mg (s) + 2H2O (I) → Mg(OH)2 (aq) + H2 (g)
The magnesium starts floating because the bubbles of
Hydrogen gas sticking to its surface.
Now , some metal like aluminium , iron, zinc do not react
with cold water or hot water. But these metals react with steam to form the
metal oxide and hydrogen gas.
2Al (s) + 3H2O → Al2O3 + 3H2 (g)
2Fe (s) + 3H2O → Fe3O4 + 4H2 (g)
Metal react with acids
Metal react with acid to form salt and hydrogen gas.
Metal + Dilute acid → Salt + Hydrogen
Zinc powder react with Hydrochloric acid to form zinc
chloride (salt) and release hydrogen gas. Here , the formation of the zinc
chloride and hydrogen which is evolved as the bubbles.
Zn (s) + 2HCl → ZnCl2 + H2
Here, nitric acid (HNO3) reacts with the metal ,
but hydrogen gas do not evolved because nitric acid (HNO3) is a
strong oxidising agent. It oxidised the H2 produced to water. And it
itself get reduced to any nitrogen oxides like N2O , NO , NO2.
Magnesium and manganese react with dilute nitric acid (HNO3 ) to form hydrogen gas.
Here, magnesium react with nitric acid to form magnesium
nitrate and hydrogen gas get evolved.
Mg + 2 HNO3 → Mg(NO3)2 + H2
Here, manganese react with nitric acid to form manganese
nitrate and hydrogen gas get evolved. Here, the rate of formation of the
bubbles is the fastest in the case of the magnesium. The reaction is most
exothermic reaction.
Mn + 2 HNO3 → Mn(NO3)2 + H2
Here, the reaction depends upon the concentration of the
acid and nature of the metal.
Why copper does not react with dilute HCl?
Here, the reactivity decreases from the Mg to Fe as in the
order Mg > Al > Zn > Fe >
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