Monday, July 7, 2014

AP Chemistry Question of the Day --60

Welcome back to my blog. Here is question 59 I posted last week.

59.  Which of the following best helps to account for the fact that the F- ion is smaller than the O2- ion?                                                     
(a) F- has a larger nuclear mass than O2-    
(b) F- has a larger nuclear charge than O2-   
(c) F- is more electronegative than O2-        
(d) F- is more polarizable than O2-.

The correct answer is b.  Both fluoride and oxygen ions have 10 electrons. They are isoelectronic to each other. The size of the ions is determined by the number of protons in the nucleus. Since fluoride has 9 and oxygen has 8 protons. The electrons in fluoride ion experience more attraction from the nucleus and makes the ions smaller.

Statement A and C are both correct but they are not the right explanation.

Here is question 60 of the series:

60. Glycerol has lower vapour pressure than does ethanol at room temperature. Which of glycerol and ethanol has the lower boiling point?

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