Preparation of Solutions and Buffers
Title:
Preparation of Solutions and Buffers
Objectives: 1. To learn and understand the theory, principle and formula behind buffers and solutions preparation. 2. To learn the methods for buffers and solutions preparation.
Introduction:
(Wikipedia, 2013) Solute is a substance dissolved in another substance. Solvent is a substance in which the solute is dissolved by it. Solution is a mixture of two or more substances. The amount of solute dissolved in a solvent is called concentration and it can be expressed in several different ways.
First and foremost, the expression of concentration can be in term of molarity. Molarity is the number of moles of solute per liter of solution. The unit of molarity is M and is read as molar.
Molarity = moles of soluteliter of solution
(Normality, 2012) Normality (N) is another way of expressing the concentration of a solution. It is based on an alternate chemical unit of mass called the equivalent weight. The normality of a solution is the concentration expressed as the number of equivalent weights (equivalents) of solute per liter of solution. The equivalent weight of a substance is depend on the reaction that the substance undergoes. In acid-base chemistry, the equivalent weight is the weight of a substance that donates or accepts 1 mole of protons. On the other hand, in oxidation-reduction reactions, the equivalent weight is the weight of a substance that loses or gains 1 mole of electrons.
N = Number of equivalents of soluteLiter of solution where Number of equivalents of solute = Grams of soluteEquivalent weight of solute
The third type of concentration expression is percent composition (% w/w). Percent composition is the percent of weight of solute in the total weight of the solution. It is expressed in grams of solute per 100 g of the solution.
Percent composition (% w/w) = Weight of solute (g)Weight of solution (g) X 100 %
Percent concentration of weight/volume (% w/v) is usually used when
Preparation of Solutions and Buffers
Objectives: 1. To learn and understand the theory, principle and formula behind buffers and solutions preparation. 2. To learn the methods for buffers and solutions preparation.
Introduction:
(Wikipedia, 2013) Solute is a substance dissolved in another substance. Solvent is a substance in which the solute is dissolved by it. Solution is a mixture of two or more substances. The amount of solute dissolved in a solvent is called concentration and it can be expressed in several different ways.
First and foremost, the expression of concentration can be in term of molarity. Molarity is the number of moles of solute per liter of solution. The unit of molarity is M and is read as molar.
Molarity = moles of soluteliter of solution
(Normality, 2012) Normality (N) is another way of expressing the concentration of a solution. It is based on an alternate chemical unit of mass called the equivalent weight. The normality of a solution is the concentration expressed as the number of equivalent weights (equivalents) of solute per liter of solution. The equivalent weight of a substance is depend on the reaction that the substance undergoes. In acid-base chemistry, the equivalent weight is the weight of a substance that donates or accepts 1 mole of protons. On the other hand, in oxidation-reduction reactions, the equivalent weight is the weight of a substance that loses or gains 1 mole of electrons.
N = Number of equivalents of soluteLiter of solution where Number of equivalents of solute = Grams of soluteEquivalent weight of solute
The third type of concentration expression is percent composition (% w/w). Percent composition is the percent of weight of solute in the total weight of the solution. It is expressed in grams of solute per 100 g of the solution.
Percent composition (% w/w) = Weight of solute (g)Weight of solution (g) X 100 %
Percent concentration of weight/volume (% w/v) is usually used when