Biochemistry : Hydrogen Bonds
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Example Questions
Example Question #11 : Molecular Bonds And Forces
Which molecule will not form hydrogen bonds?
Only nitrogen, oxygen, and fluorine can form hydrogen bonds since these three elements are very electronegative. Thus, their partial negative charge (and the presence of a lone pair of electrons) attracts a partially positive hydrogen atom. Carbon, on the other hand, is not very electronegative and thus cannot form hydrogen bonds.
Example Question #12 : Molecular Bonds And Forces
How does the strength of hydrogen bonds compare with the strength of ionic bonds?
It depends on the temperature.
Hydrogen bonds are weaker than ionic bonds.
Hydrogen bonds are just as strong as ionic bonds.
Hydrogen bonds are stronger than ionic bonds.
Hydrogen bonds are weaker than ionic bonds.
Bond strengths are measured in kilojoules/mole. Hydrogen bonds can have a strength of 
Example Question #13 : Molecular Bonds And Forces
A: adenine
U: uracil
C: cytosine
G: guanine
T: thymine
Which of the following pairs of DNA bases would require the most energy to break?
A-U
G-C
C-T
T-A
G-A
G-C
Uracil is not a base in DNA, so A-U can be ruled out as an answer. Moreover, C-G and A-T are the correct base pairs, so the other combinations can be ruled out as well. C-G requires more energy to break because there are three hydrogen bonds between these bases, while A-T has only two hydrogen bonds holding them together.
Example Question #14 : Molecular Bonds And Forces
What is a chiral center?
An atom with substituents organized such that the molecule cannot be superimposed on its mirror image.
An atom whose configuration is is rigid with no freedom of rotation.
An atom with multiple isomers.
An atom with only one double bond, but other constituents are unique.
An atom that has substituents which are unique.
An atom with substituents organized such that the molecule cannot be superimposed on its mirror image.
The substituents of a chiral center are arranged in a specific manner that cannot be superimposed on its mirror image. An example is a carbon atom with four unique substituent groups.
Example Question #15 : Molecular Bonds And Forces
Why is water conducive to hydrogen bond formation?
Water is an electric dipole.
Water is a polar solvent.
All other answers are correct.
Oxygen is electronegative.
The two hydrogen atoms are covalently bonded.
All other answers are correct.
Oxygen is more electronegative than hydrogen. This results in the electrons to spend more time with the oxygen atom making it negatively chared and the hydrogen atoms to be positively charged. The charged water molecule is then able to form hydrogen bonds with polar molecules.
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