2. Chemical Properties of Metals

Chemical properties of Metals

(i)  Reaction with air :-

All metals combine with oxygen to form metal oxide .

Metal + O₂      →     Metal oxide

For example,

2Cu  +  O₂      →    2CUO    copperoxide (black)

 4Al + 3O₂   →     2Al₂O₃     Aliminium oxide

• Sodium and potassium react so vigorously that they catch fire in open so they are kept immersed in kerosence
• Surfaces of Mg , Al, Zn pb are covered with a thin layer of oxide whish prevent them from further oxidation. Anodizing is a process of forming a tick oxide layer of aluminium.
• Iron does not burn on heating but iron filling burn vigorously.
•  Copper does not burn but the hot metal is coated with a black coloured layer of copper (ii) oxide
• Silver and gold do not react with oxygen even at high temperatures.

Amphoteric oxide  →  Metal oxides which react with both acids as well as bases to produce salts and water are called amphoteric oxides.

Example ;   

Al₂O₃   +    6HCl   →   2AlCl₃ +   H₂O

 Al₂O₃  +  2NaOH  →  2NaAlO₂    +   H₂O

                                (SODIUM ALUMINATE )

Most metal oxides are insoluble in water but some of these dissolve in water to form alkalis. Sodium oxide and potassium oxide dissolved in water to produce alkali.

Na₂O(S) +    H₂O(l)    →    2 NaOH (aq)

K₂O(S)    +   H₂O(l)     →    2 KOH (aq)

(ii)  Reactions of metals with water:-

 Metal+ water  →      Metal oxide  +  hydrogen

Metal oxide  +  water   →   metal hydroxide

 Metals like potassium and sodium react violenty with cold water.

Na  +   2 H₂O     →     NaOH + H₂  + heat energy.

The reaction of calcium of water is less violent

Ca + 2H₂O    →   Ca(oH)₂ + H₂

Magnesium react with hot water to form magnesium hydroxide and hydrogen.

Mg +  2H₂O     →  Mg(OH)₂    +  H₂

Metals like aluminium iron and zinc do not react with cold or hot water. But they react with steam to form metal oxide and hydrogen.

2 Al + 3 H₂0     →    Al₂O₃  +   3H₂

3 Fe  + 4 H₂O     →  Fe₃O₄   +   4H₂

Metal such as lead ,copper, silver and gold do not react with water at all.

(ii) Reaction of metals with acids.

Metal +  Dilute acid  →   salt + hydrogen

Copper and silver do not react wit dil acids.

 For example 

 Fe +  2HCl     →     FeCl₂  +  H₂

Mg  +  2HCl     →     MgCl₂  +   H₂

Zn  +   2HCl      →     ZnCl₂  +  H₂

(iii)   Reaction of metals with solution of other Metal salts ; 

Metal A+  Salts solution B  →    Salt solution A + Metal B   

Reaction of metals with salt solutions.

More reactive metals can displace less reactive metals from their compounds in solution form.

Fe +  CuSO₄    →      FeSO₄  +    Cu       

Fe displaces Cu because Fe is more reactive metals than Cu .

REACTIVITY SERIELS ;

The reactivity series is a list of metals arranged in the order of their decreasing activities.