AP Chemistry Question of the Day --25

Welcome back to my blog. Here comes the answer to question 24 I posted yesterday. The correct answer is D. 

From the spectra, it shows that 550eV energy is needed to remove one 1s electron from oxygen, while only 400eV is needed to remove one 1s electron from nitrogen. Since there is static attraction between the nuclear and electrons. The stronger the attractive force, the higher energy it needs to remove the electron to overcome the attraction. The strength of the static force is determined by the charge on the nuclear and the distance. In both cases, the electrons are located in the 1s shell, which means that the distances between the nuclear and the electron are about the same in O and N. The difference lies in the nuclear charge. N has 7 protons and O has 8 protons in the nuclear. As a result, O nuclear has a stronger attraction towards the electron and it takes more energy to remove the 1s electron from a oxygen atom than the 1s electron from a nitrogen atom.

Following is Question 25 of the series. 

25. 

Consider the molecules represented above and the data in the table below.

Nonane and 2,3,4-trifluoropentane have almost identical molar masses, but nonane has a significantly higher boiling point. Which of the following statements best helps explain this observation?

(A) The C–F bond is easier to break than the C–H bond.

(B) The C–F bond is more polar than the C–H bond.

(C) The carbon chains are longer in nonane than they are in 2,3,4-trifluoropentane.

(D) The carbon chains are farther apart in a sample of nonane than they are in 2,3,4-trifluoropentane

I will post the answer and explanation tomorrow. 

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