Answer
The concentration of a solution is the amount of solute (solid ) substance dissolved in the solvent ( usually water. or alcohol, or a light oil). There are several ways in which chemists express chemical concetrations of a solution-- per cent concentration , molarity , molality and mole fraction, but the two methods used most frequently are percent concentration (by mass) and molarity.
Per cent concentration; This is usually described as the mass or weight of the solute dissolved in a unit mass of solution
{( usually 100 gram(100 mls) of solution)}.
So % solution= no of parts of solute /no of parts of
solution X100/1
Parts of solute is usually in grams and parts of solution in
grams or mililiters (mls).
The molarity of a solution is described as the number of moles of solute per moles of solution . Pratically, this calculation is usually done using one liter as the denomination of the fraction thus
molarity =moles of solute/liter of solution
Percentage descriptions of concentrations are acceptable in many of the ordinary operations of life e.g. food preparation, cosmetics industry, farming etc. However for precise chemical work that aims to be peer reviwed and published, molarity descriptions of solutions are almost invariably used.
Work Step by Step
While molarity is widely used in science laboratories to describe solutions, many chemist, especially research chemists, prefer to use molality, and mole fraction descriptions to indicate solution concentrations.
Molality of a solution is the number of moles of the solute per moles of solvent ( not solution)
So Molality = moles of solute/kilograms of solvent
Mole fraction is a slightly more abstruse measuement of concentration of solutions, but it is also used, especially in the calculation of partial pressures.
Mole fraction= No of moles of solute/total number of moles of solution
Calculation of molarity, molality, and mole fraction requires accurate information about molecular weights of both solutes and solvents
