Chemical formulas; such as HClO4 can be divided into empirical formula, molecular formula, and structural formula. Chemical symbols of elements in the chemical formula represent the elements present, and subscript numbers represent mole proportions of the proceeding elements. Note that no subscript number means a subscript of 1.
The formula weight is the sum of all the atomic weights in a formula. The evaluation of formula weight is illustrated in this example.
Example 1
What is the formula weight of sufuric acid H2SO4?
Solution:The formula also indicates a mass as the sum of masses calculate this way2*1.008 + 32.0 + 4*16.0 = 98.0where 1.008, 32.0 and 16.0 are the atomic weights of H, S, and O respectively.
Discussion: If the formula is a molecular formula, the mass associated with it is called molecular mass or molecular weight. As an exercise, work out the following problem.
What is the molecular weight of caffeine, C8H10N4O2?
The diagram shown here is a model of the caffeine molecule.
With the aid of a table of atomic weights, a formula indirectly represents the formula weight. If the formula is a molecular formula, it indirectly represents the molecular weight. For simplicity, we may call these weights molar masses, which can be formula weights or molecular weights.
Example 1
What is the formula weight of sufuric acid H2SO4?
Solution:The formula also indicates a mass as the sum of masses calculate this way2*1.008 + 32.0 + 4*16.0 = 98.0where 1.008, 32.0 and 16.0 are the atomic weights of H, S, and O respectively.
Discussion: If the formula is a molecular formula, the mass associated with it is called molecular mass or molecular weight. As an exercise, work out the following problem.
What is the molecular weight of caffeine, C8H10N4O2?
The diagram shown here is a model of the caffeine molecule.
With the aid of a table of atomic weights, a formula indirectly represents the formula weight. If the formula is a molecular formula, it indirectly represents the molecular weight. For simplicity, we may call these weights molar masses, which can be formula weights or molecular weights.
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