A homogeneous mixture of different chemical substances which has uniform chemical composition through out and shows uniform physical properties is called solution. For example dissolve a small amount of copper sulphate in water the water will become blue. If this blue liquid is filtered, it will pass through the filter paper without leaving any solid. The mixture thus prepared is called a solution.
A solution which is formed by mixing two substances is called binary solution. For example solution of glucose and water.
The component of a binary solution which is in lesser amount is called solute. For example in copper sulphate solution, copper sulphate is solute.
The component of a binary solution which is in greater amount is called solvent. For example in copper sulphate solution, water is solvent.
A solution in which maximum amount of a solute has been dissolved at a particular temperature and in which the dissolved form of solute is at equilibrium with its undissolved form is called saturated solution.
Solution which can dissolve further amount of a solute at a [particular temperature is called an unsaturated solution.
The solution which contains even more amount of solute required to prepare saturated solution is called super saturated solution. The hot saturated solution of compound like sodium thiosulphate does not crystallize its solute if cooled slowly without disturbance. Such a solution is called supersaturated solution.
A solution which contains small amount of a solute as compared to the solvent is called dilute solution.
A solution which contains excess amount of a solute as compared to that of a solvent is called a concentrated solution.
The amount of solute present in given quantity of solvent is called concentration of solution. The concentration of a solution can be expressed in many ways depending upon the amount o solute and solvent present in it.
Concentration of Solution
The amount of solute present in given quantity of solvent is called concentration of solution. The concentration of a solution can be expressed in many ways depending upon the amount of solute and solvent present in it.
Percentage by Mass
The percentage of solute by mass is the mass of solute present in hundred part of the solution. For example 5% hydrogen peroxide solution by mass means that 5g hydrogen peroxide are dissolved in 95g of water to give 100g of solution.
Percentage of Mass = (Mass of Solute/Mass of Solution) x 100
Percentage by Volume
The concentration unit expresses the volume of solute present in 100cm3 of solution. For example 15% solution of alcohol by volume will mean that 15cm3 alcohols are present in 100cm3 of solution. (Here 3 represents cube)
Percentage by Volume = (Volume of Solute/Volume of Solution) x 100
The solution that contains one mole of solute in 1dm3 of solution is called a molar solution. The concentration of this solution is expressed as M.
Molarity of a solution is the number of moles of solute present in 1dm3 of the solution. It is expressed as M.
M = Number of Moles of Solute/Volume of Solution in dm3
M = (Mass of solute/Molecular Mass) x (1/ Volume of Solution in dm3)
The process in which crystal separates from saturated solution on cooling is called crystallization. It is a useful process because it can be used to purify the impure solid compounds. It can also be used to separate a mixture of solids.
The ions surrounded by solvent molecules in solution are called solvated ions. If water is a solvent these ions are called hydrated ions.
A suspension in such a mixture in which solute particles do not dissolved in solvent and if filtrated its particles do not pass through the pores of filter paper.
In a colloidal solution the solute particles are slightly bigger than those present in a true solution but not big enough to seen with naked eye.
A solution whose molarity (strength) is known is called Standard Solution.
A True Solution is such a mixture in which solute particles are completely homogenized in the solvent for example solution of sodium chloride or copper sulphate in water.
Solubility o a solute in a particular solvent is defined as the amount of solute in grams, which can dissolve in 100g of the solvent at a particular temperature to give a saturated solution.
The amount of a solute in gram moles, which can dissolve in one kilogram of the solvent at a particular temperature, to give a saturated solution.
Factors Affecting the Solubility
Effect of Solvent
Similar solvents dissolve similar solutes, i.e. if the chemical structure and the electrical properties such as dipole moment of solute and solvent are similar, the solubility will increase. If there is dissimilarity in properties, then either the solute will not dissolve or there will be very little solubility.
Effect of Solute
Different solutes have different solubility’s in a particular solvent e.g. if the saturated solutions of table sugar and sodium chloride are prepared, it is found that the concentration of sodium chloride solution is 5.3 molar while that of sugar solution is 3.8 molar. In other words, the solubility of sodium chloride in water is far greater than that of sugar. This is due to the fact that the attraction of sodium (Na+ and chloride (Cl-) ions with water is greater than that of sugar molecules with water.
Effect of Temperature
Change in temperature has different effects on the solubility of different compounds. Usually the solubility increase with the increase in temperature but it cannot be taken as a general rule. The solubility of compounds like lithium carbonate, calcium chromate decreases with the increase in temperature. The solubility of gases in water also decreases with the increase in temperature. On the other hand, there are a large number of compounds whose solubility in water increase with the increase in temperature e.g. sodium nitrate, silver nitrate, Potassium chloride etc. the solubility of sodium chloride in water does not increase appreciably with the increase in temperature.