CHM 1046
General Chemistry II
Dr. Michael Blaber


Aqueous Reactions

Properties of Solutes in Aqueous Solutions


 

 Solvent versus Solute

The molecular mass of H2O = (2*1.008) + 15.999 = 18g/mole

The density of H2O is 1g/ml * (1000ml/L) = 1000g/L

The molar concentration of pure H2O is therefore: (1 mole/18g) * (1000g/L) = 55.6 moles/L

 

How does water "dissolve" a solute?

The polar nature of the water molecule

It is the ability of water to participate in these diverse non-covalent interactions that allows water to "dissolve" a variety of solutes

Ionic Compounds in Water

Water can participate in ion-dipole interactions.

 


Distinctions between concentrations of ionic compounds and resulting concentrations of ions in an aqueous solution

 

An electrolyte solution (a solution of ions) can be described by either the concentration of the ionic compound that was dissolved, or by the relative concentrations of the anion and cation components


Molecular compounds in an aqueous solution

Example: Methanol (CH3OH) mixed with water


Strong and weak electrolytes

For example, acetic acid only partially ionizes (i.e. is a weak electrolyte) when dissolved in H2O. This ionization involves the breaking of a covalent bond between an oxygen and hydrogen atom in the acid:

Chemists use a double arrow to indicate the ionization of weak electrolytes, and a single arrow to indicate the ionization of strong electrolytes (i.e. in strong electrolytes, the ions have essentially no tendency to recombine to form the neutral compound)


© 2000 Dr. Michael Blaber