Question

What type of intermolecular force would water molecules have? London dispersion? Dipole-dipole? Or hydrogen bonding?

Answer 1

Hint :Remember the structure of a water molecule $H_{2}O$ and the presence of a polar covalent bond between the highly electronegative $O$ atom and $H$ atom. We can see that the molecule has a net dipole moment. Use these observations, to find the types of intermolecular forces acting.

Complete Step By Step Answer:
First let us understand about intermolecular forces and different kinds of forces. Particles experience forces of attraction or repulsion between neighboring particles and such forces are known as intermolecular forces (atoms, molecules, or ions). In comparison to intramolecular forces like covalent or ionic bonds between atoms in a molecule, these forces are weak. There are mainly three kinds of intermolecular forces, which are:
(i) Dipole-dipole interactions: These forces occur when the partially positively charged part of a molecule interacts with partially negatively charged part of the neighboring molecule. Partially charged ions are needed for this form of attraction to occur.
(ii) Hydrogen bonding: It is a form of dipole-dipole interaction that occurs when a hydrogen atom is bonded to a highly electronegative atom, which are oxygen, nitrogen and fluorine. The partially positive end of hydrogen attracts the partially negative end of another molecule's oxygen, nitrogen, or fluorine.
(iii)London dispersion forces: They exist between all forms of molecules, whether ionic or covalent, polar or nonpolar, and are the weakest of the intermolecular forces. The higher the London dispersion forces are, the more electrons a molecule has.
We know that the bonding between hydrogen and oxygen atoms in a water molecule is a polar covalent bond, with more electron density on the electronegative $O$ atom. Because of this the partially positive $H$ atom from another molecule is attracted towards this $O$ atom. We can clearly see the existence of hydrogen bonding between molecules as $H$ is bonded to $O$ . Hydrogen bonding is in fact a special type of dipole-dipole interaction, so water molecules have dipole-dipole interactions as well. London dispersion forces exist between all types of molecules, so they are present in water molecules as well.
Hence, water molecules have all three types of intermolecular forces.

Note :
Hydrogen bonding is a relatively strong force when compared with other types. And so, we need more energy to break such bonds and this explains the high boiling point of water. Remember that all molecules have London dispersion forces.