Passage I
Table 1 lists the name, chemical formula, molecular mass (the mass of 1 molecule in atomic mass units, amu), and BP (the boiling point at 1 atmosphere of pressure) of various compounds. The first compound listed is composed of the elements carbon (C) and hydrogen (H). Each of the other compounds is composed of C, H, and either fluorine (F), chlorine (Cl), bromine (Br), or iodine (I). The elements F, Cl, Br, and I belong to the halogen family.
Table 1 adapted from W. M. Haynes, ed., CRC Handbook of Chemistry and Physics on CD-ROM, Version 2011. @2011 by CRC Press. LLC.
Figure 1 shows a plot of BP versus molecular mass for 3 groups of compounds (Groups 1-3). Each compound in each group is composed of C and 1 or more halogens.
Figure 1 adapted from Michael Laing, "Boiling Points of the Family of Small Molecules, CHwFxClyBrz: How Are They Related to Molecular Mass?" @2001 by Division of Chemical Education, Inc., American Chemical Society.
6. The atomic mass (the mass of 1 atom, in amu ) of C is 12 amu. Based on the molecular mass of CBr4 shown in Figure 1, the atomic mass of Br is closest to which of the following ?
Your Answer is
Correct Answer is H
Explanation
From figure 1, it can be seen that the molecular mass of CBr4 is 330, and the atomic mass of a C is 12, so the atomic mass of Br is equal to (330-12)÷4≈80