Molecular formula, calculation

Atoms and their symbols were introduced in Chap. 3 and 1. In this chapter, the representation of compounds by their formulas will be developed. The formula for a compound (Sec. 4.3) contains much information of use to the chemist. We will learn how to calculate the number of atoms of each element in a formula unit of a compound. Since atoms are so tiny, we will learn to use large groups of atoms—moles of atoms—to ease our calculations. We will learn to calculate the percent by mass of each element in the compound. We will learn how to calculate the simplest formula from percent composition data, and to calculate molecular formulas from simplest formulas and molecular weights. The procedure for writing formulas from names or from knowledge of the elements involved will be presented in Chaps. 5. ft. and 13. 

Once the desired structure is generated the user should be able to use its representation (the connection table) in many different ways to store it, to combine it with other structures, supplement it with textual information, to decompose it to fragments, add it to a collection, use it as a target or query compound in different searches or procedures, use it in different applications such as simulation of spectra, determination of properties, etc. calculate molecular formula, draw it on a plotter, etc. 

With empirical formulas (Section 7.4) and molar masses, we can calculate molecular formulas (Section 7.5). 

Sample Study Sheet 9.3 Calculating Molecular Formulas... 

If you answered incorrectly, review Calculating Molecular Formulas, page 146. 

Check The calculated molecular formula has the same ratio of moles of elements (3 6 3) as the empirical formula (1 2 1) and corresponds to the given molar mass ... 

Interconvert masses, moles,and formulas Determine percent compositions in compounds Determine formulas from composition data Recognize models from calculated molecular formulas Perform calculations on the purity of substances... 

EXAMPLE 6.13 Calculating Molecular Formula from Empirical Formula and Molar Mass... 

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