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 >