Hydrogen bonding Flashcards Preview

CHEM - 2.2.2 Shape of Molecules and Intermolecular Forces > Hydrogen bonding > Flashcards

Flashcards in Hydrogen bonding Deck (4)
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What are Hydrogen bonds?

- Special type of permanent dipole-dipole interaction found between molecules containing a strongly electronegative atom with lone pairs (like oxygen, fluorine and nitrogen) and hydrogen atoms
- Hydrogen bond acts between a lone pair on a EN atom in one molecule and a hydrogen atom in a different molecule


Why is water perfect for hydrogen bonding?

- Unlike others it has 2 lone pairs AND two hydrogens so it is not limited by anything.
* Due to H.Bonding water has anomalous properties


Why is the ice less dense than water?

- Hydrogen bonds hold water molecules apart in an open lattice structure

- The water molecules in ice are further apart than in water. This is because water can form 4 hydrogen bonds and when all are formed, it makes the bond extend outwards which holds water molecules slightly apart as a tetrahedral lattice full of holes.

- Solid ice is less dense than liquid water and it floats. The holes in the open lattice structure collapses and molecules move closer making water more dense.


Why does water have a relatively high melting and boiling point?

- Hydrogen bonds are extra forces
- More energy is needed to break hydrogen bonds in water