Water, pH and Macromolecules
Which of the following statements about covalently bonded molecules is false?

Noncovalent bonds may also be present, especially if the molecule is large
Electrons are shared between the atoms that make up the molecule
Such molecules often result from the interaction of ionized atoms
The chemical bonds that hold the molecule together are relatively strong

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Water, pH and Macromolecules
Salt dissolves well in water as water molecules

form hydrogen bonds with the positively and negatively charged ions
make nonpolar covalent bonds with the positively charged ions only
surround the ions because of their charge but do not form hydrogen bonds
share electrons with the ions to make polar covalent bonds

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Water, pH and Macromolecules
The main difference between an acid and a base is that

bases are polar molecules and acids are not
acids donate hydrogen ions in water while bases accept hydrogen ions
acids are polar molecules and bases are not
bases donate hydrogen ions in water while acids accept hydrogen ions

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Water, pH and Macromolecules
Buffer solutions

are rarely found in living systems
will always have a pH of 7
tend to maintain a relatively constant pH.
cause a decrease in pH when acids are added to them.

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