|Whenever possible, reactions are carried out
with all of the reactants in the same fluid phase.
|This means that it is preferrable to have liquids reacting with liquids,
or gases reacting with gases. This is because no matter what type of particle
we talk about, in order for them to react they must collide with each other.
Solids have little or no movement and therefore offer few opportunities for
collision. Liquids and gases are both fluids and offer much more opportunity
for frequent collision. Liquids are used in the lab because they are
fairly easy to create and use. Gases are used but specialized gas handing
equipment is required.
|A solution is a uniform mixture of particles of atomic, ioncic,
or molecular size. A minimum of two substances are present. One
is called the solvent and all the others are called the solutes.
The solvnet is the fluid medium in which all of the solutes are dissolved.
A solvent can be a solid, liquid or a gas but the most common solvent is water
and therefore we deal almost exclusively with aqueous solutions.
Solutes are any substance dissolved in the solvent.
|A dilute solution is one in which the ratio of solute to solvent
is very small, for example, a few crystals of sugar in a glass of water.
In a concentrated solution the ratio of solute to solvent is large.
Maple syrup is a concnetrated solution of sugar in water. A saturated
solution is one in which no more solute can be dissolved at a particular
temperature. An unsaturated solution is one in which the ratio
of solute to solvent is lower than that of the corresponding saturated solution.
If more solute is added to an unsaturated solution, at least some of it should
dissolve. A supersaturated solution is an unstable system
in which the ratio of dissolved solute to solvent is higher than that of
a saturated solution. A supersaturated solution can be made by gently
cooling a hot saturated solution. At a lower temperature the dissolved
solute can be made to precipitate out when a seed crystal is added.
The process is called precipitation and the substance that forms is
|The amount of solute needed to make a saturated solution in a given
quantity of solvent at a specific tempeature is called the solubility
of the solution.