Chemical Reactions
COMBINATION, DECOMPOSITION,DISPLACEMENT, DOUBLE DISPLACEMENT REACTIONS
Definition of chemical change:
A change in which new substances are formed is called Chemical change.
Ex: Curdling of milk, Burning of paper, Rusting of iron....
Definition of chemical reaction:
The reaction where chemical change takes place is called chemical reaction.
Types of chemical reactions:
1. Chemical Combination reaction
2. Chemical Decomposition reaction
3. Displacement reaction.
4. Double displacement reaction.
CHEMICAL COMBINATION REACTIONS
The reaction in which a single product is formed from two or more reactants is called combination reaction.
The reactants, A and B, combine to form a new single product, AB, which is always a compound. An example of a combination reaction is when hydrogen and chlorine react to form hydrochloric acid
reaction product
\(
H_2 + Cl_2 \to 2HCl
\)
It is also called as synthesis reaction when two elements combined to give single product .
EXAMPLES
When solid sodium metal combine with chlorine gas to form solid sodium chloride. The equation can be written as follows
2Na(s)+Cl2(g \(
\to
\) 2NaC
Another frequently occuring combination reaction is that an element combine with oxygen to form its oxide. When magnesium reacts rapidly when ignited, combining with oxygen to form a fine powder of magnesium oxide.
The equation can be written as follows
2Mg(s)+O2(g) \(
\to
\) 2MgO(s)
Sulphur reacts with oxygen to form sulphur dioxide
Sulphur + Oxygen \(
\to
\) Sulphur dioxid
\(
S + O_2 \to SO_2
\)
One typical example of combination reaction is formation of “Acid rains”.
FORMATION OF ACID RAIN:
Acid rains are formed due to pollutants like sulphur trioxide present in atmosphere. In atmosphere,sulphur trioxide gas reacts with water to form an acid called sulphuric acid.Now this acid fall to the earth as acid rain.
SO3(g)+H2O(I) \(
\to
\) H2SO4(l)
Tajmahal is losing its shining due to effect of acid rains.