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| Chemical Formulae
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| Every chemical substance is known by a specific name. But these names can sometimes be cumbersome, confusing and not provide sufficient information about its chemical composition. To overcome this, each chemical compound is represented by a chemical formula that gives its composition (constituent elements present) and the number of elements of each type present. A formula will represent only the simple ratio of positive and negative ions.
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| Molecular formula
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| A chemical formula that represents the composition of a molecule of the substance in terms of the symbols of the elements present in the molecule is also called molecular formula. Discrete molecules can be described by this formula. As it represents one molecule of the substance giving the names and number of atoms of the various elements present, it denotes the molecular mass of the substance.
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| For example, the molecular formula of water is H2O, which means that one molecule of water contains two atoms of hydrogen and one atom of oxygen. This also represents the molar mass, which is the sum of the gram atomic mass of all the atoms.
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| Gram atomic mass of 2 hydrogen atoms = 2 x 1.008 g
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| Gram atomic mass of oxygen atom = 16 g
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| Total molecular mass = 18 g
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| * (Please insert the necessary information to
link to the slide and animation part on the topic of writing chemical
formulae. Refer to the 3.4 section of the NCERT chapter. Also give the
table of common ions)
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| Molecular Formulae of Important Acids
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| Molecular Formulae of Important Bases
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| Molecular Formulae of Important salts - Oxides
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| Molecular Formulae of Important salts - Carbonates and Bicarbonates
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| Significance of Molecular Formula
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It represents name of the substance
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It represents one molecule of substance
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It gives the names of all the elements present in one molecule of the substance. It also gives the number of atoms of each element present.
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It represents a definite mass and refers to the presence of 6.023 x 1023 molecules (known as the mole concept).
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