Phys 1345 Page 1 Hydrogen Bonding MANY objects at the molecular level have their positive and negative charged separated. Because of this, such molecules-even neutral molecules-can attract one another simply by causing one another to rotate into a favorable orientation. One example of this is hydrogen bonding of water molecules. This is the primary mechanism that creates surface tension in water (and a similar phenomenon plays a big role in a variety of biochemistry). Within a single water molecule, hydrogen atoms are positive (te) and the oxygen atom is negative (-2e). Electric forces and the quantum sharing of electrons hold the whole molecule together, but we won't worry about what's happening inside the molecule, here. Instead, we will explore how the electric forces between properly arranged water molecules winds up being attractive. 1 A Model of Hydrogen Bonding The angle between the hydrogen atoms in a water molecule is actually 104, but in order to reduce your calculation for the purpose of this problem, we'll treat them as if they were a right angle 90. In a water-water hydrogen bond, the separation between the hydrogen in one molecule and the oxygen in the other is about twice the distance between the hydrogen and the oxygen in its own molecule. Our simplified model is sketched in the figure below (note: don't forget that atoms A and D both have a charge of -2e). d 2d OB D CO 3. Consider the "backbone" charges A, B, and D. A and D repel, but B and D attract. Who wins? Does the combined (AB) attract or repel D? By how much? d 2d OB Express your answer as a multiple of kee d2 which is the force between two charges, e, at a distance d