Molecular Forces

Question 1

electrostatic interactions - ion pairs

Answer 1

full positive with full negative; very strong (86 kJ/mol); over long distances (10 A) strength falls off slowly over distance (1/d^2); dependent on pH

Question 2

electrostatic interactions - dipole-dipole

Answer 2

weaker than ion pairs (9 kJ/mol); caused by charge separation in neutral molecules (polarity); less distance than ion pairs (3-10 A)

Question 3

hydrogen bonding

Answer 3

electron pair donor & acceptor; H shared between atoms; linear & close (1.5-2 A) –> stronger than other dipole-dipole interactions

Question 4

van der waals interactions

Answer 4

occur between all atoms; weak individually (0.3 kJ/mol) but together can be strong; (atoms repel when close (1/r^12), but attract a lot when separated a specific distance (1/r^6); dependent on size of atoms)

Question 5

hydrophobic interactions

Answer 5

don’t interact with water; energetically unfavorable to disrupt water network maintained by H bonds; thus hydrophobic molecules are excluded, cluster together