Passage VII
A chemist studied nonpoisonous fluorocarbons, compounds composed of only carbon (C) atoms and fluorine（F) atoms, for potential use as blood substitutes. In order to be effective, the fluorocarbons had to be chemically stable at body temperature (37°C), able to transport oxygen (O2) from the lungs to the tissues, and able to transport carbon dioxide (CO2) from the tissues to the lungs. Chemical substitutes for blood are studied because they can be stored for long periods of time, do not carry diseases, and do not have compatibility problems with different blood types.
Experiment 1
The stability of five fluorocarbons was determined by measuring the strengths of their chemical bonds in kilocalories per mole (kcal/mol). The higher the average bond strength, the more stable the compound. The results are in Table 1.
Experiment 2
The amount of O2 or CO2 gas that dissolves in each fluorocarbon was measured by weighing out 100 g each of Fluorocarbons A-E, bubbling the O2 or CO2 through the fluorocarbon for one hour, and determining the mass of the resulting solution. The results are in Table 2.
Experiment 3
The time the body takes to decompose and eliminate the blood substitute was studied by measuring the amount of fluorine present in urine. The chemist found that, for each of Fluorocarbons A-E, the fluorine level rose to a maximum and then declined over a period of several days.
37. Why are only C—C and C—F bond strengths reported by the chemist?
Your Answer is
Correct Answer is D
Explanation
flourocarbon only contains C and F, but because F has seven outer electrons, it cannot form a covalent bond with itself, so there are only two bonds that may be formed in the article. (If you don’t have background knowledge, just use the method of exclusion, other options are outrageous)