Chemical Properties of Metals

Let’s check reactions of metals with

• Reaction of metals with Oxygen

• Reaction of metals/non metals with Water
• Reaction of metals/non metals with Dilute Acids
• Reaction of metals/non metals with Salt Solutions
• Reaction of metals/non metals with Chlorine
• Reaction of metals/non metals with Hydrogen

Reaction of Metals with Oxygen (Air)

When a metal burns in air, it forms a metal oxide .

Thus, 

           Metal + Oxygen → Metal Oxide

examples:

Copper is heated in air, it combines with oxygen to form copper(II) oxide , a black oxide.

2Cu + O ₂ → 2 CuO  

               (Copper)            (Copper(II) oxide)

Similarly, aluminium forms aluminium oxide . 

4Al + 3O ₂ → 2 Al ₂ O ₃  

           (Aluminium)          (Aluminium oxide)

• Metal oxides are basic in nature. 

• Metal oxides turn red litmus blue .
• Some metal oxides can be neutral.

Reactions of some metals are given below:

SODIUM AND POTASSIUM (Alkali Metals)

• Sodium and Potassium react vigorously with oxygen at room temperature to form basic oxides called Sodium oxide and Potassium oxides respectively. 

MAGNESIUM 

• On heating, magnesium metal burns in air giving an intense heat and light to give a basic oxide, magnesium oxide.
• Magnesium oxide is partially soluble in water, and forms Magnesium Hydroxide.

ALUMINIUM  

• On strong heating in air, aluminium forms a metal oxide called aluminium oxide.
• Metal oxides of Aluminium show both acidic and basic behaviour and react with both acids and bases to form salt and water, thus, they are called amphoteric oxides .

Reactions are as follows :

Amphoteric oxides react with both acids and bases to form salt and water :

With acids, Aluminium oxide behaves like a basic oxide.

With bases, Aluminium oxide behaves like an acidic oxide.

ZINC  

• Zinc metal burns in air only on strong heating.
• Zinc oxide also behaves as an amphoteric oxide, thus reacts with both acids and bases to give corresponding salts and water.  

Reactions of Zinc with oxygen to give Zinc oxide :

IRON 

• Iron forms iron (II and III) oxides on heating.
• This metal rusts easily on exposure to moisture, hence it must undergo certain processes to avoid rusting.

Reaction of Formation of Iron Oxide is as follows :

COPPER 

• On prolonged heating in the presence of air, copper metal forms a black oxide called Copper (II) oxide (CuO), which is completely oxidised unlike Cuprous oxide (Cu 2 O 3 )

Reaction is as follows :

Reactions of Metals with Water

Metals react with either Hot or Cold Water to form a metal hydroxide and Hydrogen gas.

Metals react with Steam to give metal oxide and hydrogen gas.  

Reaction of Sodium and Potassium with COLD WATER.

• It is a highly exothermic reaction , a high amount of energy is released. 
• Hydrogen gas formed during the process catches fire immediately. 
• Sodium an Potassium are very reactive metals .

Calcium - COLD WATER.

• Calcium metal reacts with water to form calcium hydroxide .
• Bubbles of hydrogen released stick to the surface of calcium metal, making it float.
• The reaction is exothermic, but Hydrogen does not burn /explode.

Magnesium - HOT WATER.

• Magnesium metal reacts with hot water to form Magnesium hydroxide .
• Bubbles stick to the surface of the metal, making it float around in water. 

• This reaction is faster than the one with hot water, since this occurs at a higher temperature.

Aluminium - STEAM.

• Reacts with steam to form aluminium oxide and hydrogen. 
• Under ordinary conditions, no reaction takes place as there is a thin but tough layer of oxide on the surface of aluminium metal.

Zinc - STEAM.

• Zinc reacts with steam to give zinc oxide and hydrogen.
• Zinc is less reactive than aluminium.

 Iron - STEAM.

• Iron reacts with steam to give iron (II & III) oxide.
• Iron is less reactive than Zinc.

Metals like Copper, Gold, Silver, Platinum do not react with water.

Reaction of Metals with Dilute Acids

Metals reacting with acids liberate hydrogen from dilute acids , to form salts.

Reactions of Metals with Dil. HCl

Metals react with dil. HCl to give metal salt+Hydrogen.

• Sodium and Potassium - React violently with HCl to form Sodium and Potassium chloride with hydrogen gas.

• Magnesium and Calcium- React rapidly with Dil. HCl, giving Magnesium Chloride and Calcium Chloride with Hydrogen gas.

• Aluminium - Initially reacts slowly due to the presence of an oxide layer on its surface.
  

• However the acid slowly wears off the oxide layer exposing fresh metal which reacts to form Aluminium chloride and hydrogen gas.

• Zinc - Reacts to form zinc chloride and hydrogen gas.

• Less rapid reaction as compared to aluminium.

• Iron - Reacts to form Iron (II) Chloride (FeCl ₂ ) and H ₂

• Reaction is less rapid than that of Zinc.

Copper, gold, silver, platinum do not react with Dil. HCl .

Reactions with Dil. Sulphuric acids :

Metals react with dilute sulphuric acid to give metal sulphates and hydrogen . 

The reactions for these metals are given below.

Metal+Acid -> Metal Sulphate + Hydrogen gas

Similarly, other salts such as Zinc, Iron, Aluminium and Magnesium react with Dil. H ₂ SO ₄ to give their metal sulphates and hydrogen gas.

Metals like Gold, Copper, Silver and Platinum do not react with Dil. H ₂ SO ₄

Reactions with Dil. Nitric Acid :

1. Magnesium - Reacts with very dilute nitric acid to give Magnesium nitrate and hydrogen .

• Very dilute nitric acid is a weak oxidising agent , thus it cannot oxidise hydrogen to water. 
  

Aluminium and Zinc form similar salts with HNO ₃ .

2. Manganese - Reacts with very dilute acid to give manganese nitrate and hydrogen .

• Less reactive than Magnesium.

 Metals like Copper, Gold, Silver, Mercury and Platinum, do not react with dil HNO3 under normal circumstances.