Friday, 16 March 2012
Types of Chemical Reactions
There are six basic types of chemical reactions. These include synthesis reactions, decomposition reactions, single replacement reactions, double replacement reactions, combustion reactions and acid-base reactions.
There are six basic types of chemical reactions. These include synthesis reactions, decomposition reactions, single replacement reactions, double replacement reactions, combustion reactions and acid-base reactions.
· Synthesis Reactions: Such reactions involve two or more simple reactants to combine together and yield a more complex substance.
For
example, hydrogen gas combines with oxygen to form a more complex product,
water. The chemical equation of this reaction looks as follows:
2H2 + O2 = 2H2O
2H2 + O2 = 2H2O
· Decomposition Reactions: In this type of chemical reaction, a complex
substance breaks down into some simple substances. A single reactant produces
two or more products. For example, a water molecule can be broken down into
hydrogen and oxygen. This chemical reaction can be presented as:
2H2O = 2H2+ O2
2H2O = 2H2+ O2
· Single Replacement or
Displacement Reaction: In this kind of
reaction, a less active element is replaced by a more active element present in
a compound. Two reactants produce two products. For example, when zinc reacts
with hydrochloric acid, hydrogen molecule is replaced by zinc to form ZnCl2.
This reaction looks like:
Zn + 2HCL = ZnCl2 + H2
Zn + 2HCL = ZnCl2 + H2
· Double Replacement or
Displacement Reaction: In this chemical
reaction, the cations and anions of two different substances switch their
places to yield two totally different compounds. For example, when silver
nitrate reacts with sodium chloride, sodium and silver switch their places and
there is a formation of sodium nitrate and silver chloride. The chemical
equation of this reaction is:
AgNO3 + NaCl = AgCl + NaNO3
AgNO3 + NaCl = AgCl + NaNO3
· Combustion: During this chemical reaction, a hydrocarbon
is burnt in the presence of oxygen to form carbon dioxide (in complete
combustion), or carbon monoxide (in partial combustion due to a limited amount
of oxygen). This reaction can be presented as:
C10H8 + 12O2 = 10CO2 + 4H2O
C10H8 + 12O2 = 10CO2 + 4H2O
· Acid-base Reaction: It is a special type of double displacement
reaction, which is characterized by the reaction between an acid and a base. In
this chemical reaction, H+ ion in the acid reacts with OH- ion
present in the base, leading to formation of water. Generally, the end products
of this reaction are water and some ionic salts. For example, hydrobromic acid
reacts with sodium hydroxide to yield water and NaBr. The equation of this
chemical reaction is:
HBr + NaOH = NaBr + H2O
HBr + NaOH = NaBr + H2O
Wednesday, 14 March 2012
Interesting Facts about Ammonia
Ammonia, the only common alkaline gas, turns the red litmus
solution blue. This is because of very high solubility of ammonia in water .
NH3 + H2O(l) ⇌ NH4+(aq)
+ OH-(aq)It is the presence of OH- ions which make the solution alkaline.
Relative
atomic mass is defined as the ratio of the average atomic mass
number of the different isotopes of that element which is weighted by abundance
to the unified atomic mass unit. It is the weighted mean of the atomic masses
of all the atoms of a chemical element found in a particular sample, weighted
by isotopic abundance.
Relative
atomic mass (RAM) of an element is the number of times one atom
of an element is heavier than 1/12 the mass of an atom of carbon [C12].
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