The average mass of a chloroform molecule, CHCl 3, is 119.37 amu, which is the sum of the average atomic masses of each of its constituent atoms. Figure 1 outlines the calculations used to derive the molecular mass of chloroform, which is 119.37 amu. The average molecular mass of a chloroform molecule is therefore equal to the sum of the average atomic masses of these atoms. The molecular formula of chloroform indicates that a single molecule contains one carbon atom, one hydrogen atom, and three chlorine atoms. Consider chloroform (CHCl 3), a covalent compound once used as a surgical anesthetic and now primarily used in the production of the “anti-stick” polymer, Teflon. Formula Mass for Covalent Substancesįor covalent substances, the formula represents the numbers and types of atoms composing a single molecule of the substance therefore, the formula mass may be correctly referred to as a molecular mass. These ideas can be extended to calculate the formula mass of a substance by summing the average atomic masses of all the atoms represented in the substance’s formula. In an earlier chapter, we described the development of the atomic mass unit, the concept of average atomic masses, and the use of chemical formulas to represent the elemental makeup of substances. Understanding the relationship between the masses of atoms and the chemical formulas of compounds allows us to quantitatively describe the composition of substances. For example, Dalton’s atomic theory was an attempt to explain the results of measurements that allowed him to calculate the relative masses of elements combined in various compounds. We can argue that modern chemical science began when scientists started exploring the quantitative as well as the qualitative aspects of chemistry. Define the amount unit mole and the related quantity Avogadro’s numberĮxplain the relation between mass, moles, and numbers of atoms or molecules, and perform calculations deriving these quantities from one another.Calculate formula masses for covalent and ionic compounds.By the end of this section, you will be able to:
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