Types of Solution There are different types of solutions based on their distinct properties. They are 1. 2. 3. 4. 5. 6. 7. 8. 9. Aqueous Solutions Non aqueous Solutions Concentrated Solutions Dilute Solutions Saturated Solutions Unsaturated Solutions Supersaturated solutions Solid solutions Gaseous solutions 1. Non - Aqueous Solutions It is a solution where the solvent is something other than water. For example, iodine in alcohol, acetone in benzene are example of non-aqueous solution. 2. Concentrated Solutions and Dilute Solutions Between two solutions, the solute quantity may be different. The solution that has more proportion of solute is said to be concentrated. If the proportion of solute is less, the solution is a dilute solution. The concentration of a solution is expressed as the amount of solute present in a given amount (mass or volume) of the solution; or the amount of solute dissolved in a given mass or volume of a solvent. It is expressed as a percentage of these quantities. 3. Supersaturated solutions The solubility of the salt will increase with increase in temperature. Hence we can add more solute to the saturated solution at an elevated temperature (nearly at its boiling point). A solution where the solute cannot be added further even at elevated temperature is called a super saturated solution. It is highly unstable and the solute will crystallize when the temperature is reduced. 4. Gaseous solution Gases diffuse uniformly to form a homogeneous mixture. Air is such a homogeneous mixture of many gases like nitrogen, oxygen, carbon dioxide etc. A gaseous solution is a uniform solution of two or more non reactive gases. Concentration of Solutions The concentration of solution is expressed in different terms. 1. Volume/volume percent: It is the volume of solute present in 100ml of solution. It is the most common method used when both solute and solvent are liquids. It is denoted by v/v. For example, if it is shown that the concentration of ethanol is 15% v/v, it means that 15ml of ethanol is present in 100ml of solution. 2. Mass/mass percent: It is the mass of solute present in 100g of solution. It is denoted as w/w. It is commonly used when the solute is in solid state. For example, if it is shown that the concentration of glucose solution in a bottle as 10% w/w. It means that 10g of glucose is present in 100g solution. 3. Moles per liter/Molarity: It is the number of moles of solute present in 1 liter of solution. It is expressed in moles/liter. 4. Moles per kg of solvent/molality: It is the number of moles of solute present in 1kg of solvent. It is expressed in moles/kg. 5. Mole fraction: It is the ratio of the number of moles of one component to the total number of moles in the system. Generally the sum of the mole fractions of all components is equal to 1. Solubility Solubility is a measure that denotes the maximum amount of substance that can be dissolved in a solvent in a saturated solution. It is the amount of solute present in 100ml of a saturated solution at a particular temperature. It depends on temperature, nature of substance, pressure. 1. Temperature: Temperature is directly related with solubility. When we increase the temperature, more energy is given to break the molecules. Hence the solubility increases on increasing the temperature. 2. Nature of substance: In solubility 'like dissolves like', which means that non polar substances can dissolve well in non polar solvents like benzene etc. Similarly polar substances like sodium chloride will dissolve in polar solvents like water. 3. Pressure: Pressure will affect the solubility of a gas in a liquid. Hence the solubility of gas is directly related to the pressure of the gas over the liquid. It is well known as Henry's law. The other term closely related with solubility of the substance is 'solubility product'. It is the product of the concentration of ions produced in a solution at a particular concentration. Properties of Solution The solution is homogeneous, which means that both solute and solvent are in the same state which cannot be differentiated easily. The solution is stable, which means that the solute particles will not settle down in time. The properties of a solution are different from the solute and solvent. In the case of solid solutions like alloys, the properties like melting point, refractive index are entirely different from the parent metals. Similarly for liquid solutions, the melting point and boiling point are different from a pure solvent. Aqueous Solution In the solution if the solvent is water it is called an aqueous solution. For example sodium chloride in water and copper sulphate in water are some examples for aqueous solution. Water is a universal solvent. Due to the high dielectric constant and high intermolecular space, the solutes can undergo either dissociative dissolving or undissociative dissolving. For example sodium chloride breaks up as sodium and chloride ions in water but sugar molecules retain their identify in solution level also. Saturated Solution Saturated solution is a solution to which no more solute can be added at a particular temperature. As temperature affects the solubility of a substance, a saturated solution at lower temperature may become a dilute solution at higher temperature. Unsaturated Solution It is a solution to which more solute can be added to dissolve. They are also otherwise called dilute solutions. The concentration of a solution is very low in an unsaturated solution. Solid Solutions It is the type of solution in which both solute and solvent are solids. For example metal alloys are a homogeneous mixture of two or more metals and their properties are entirely different from the parent metals. Liquid Solutions In a solution if both the solute and solvent are liquid they are called as liquid solutions. Ethanol in water, Benzene in carbon tetra chloride are example for liquid solutions. Types of solutions All the three states of matter (gas, liquid or solid) may behave either as solvent or solute. Depending on the state of solute or solvent, mainly there may be following nine types of binary solutions. Solvent Solute Example Gas Gas Mixture of gases, air. Gas Liquid Water vapors in air, mist. Gas Solid Sublimation of a solid into a gas, smoke. Liquid Gas CO2 gas dissolved in water (aerated drinks). Liquid Liquid Mixture of miscible liquids, e.g., alcohol in water. Liquid Solid Salt in water, sugar in water. Solid Gas Adsorption of gases over metals; hydrogen over palladium. Solid Liquid Mercury in zinc, mercury in gold,CuSO4.5H2O. Solid Solid Homogeneous mixture of two or more metals (alloys), e.g., copper in gold, zinc in copper. Among these solutions the most significant type of solutions are those which are in liquid phase and may be categorized as, (1) Solid in liquid solutions, (2) Liquid in liquid solutions and (3) Gas in liquid solutions. Properties of Water A. Cohesive behavior 1.Explanation: Water molecules form hydrogen bonds with one another causing high surface tension. 2. Eg. a water strider walks on the surface of a pond. Lab- Pepper floats on surface of water until soap is added. Water droplets form bubble on the top of a penny. B. Adhesive behavior 1.Explanation: Water Molecules form hydrogen bonds with other polar molecules causing capillary action. 2.Eg. Water crawls up a narrow glass tube and paper. Lab- water advances up paper down when tip is dipped in. C. High heat capacity 1.Explanation: Hydrogen bonding causes H2O to absorb a large amount of heat before its temperature increases appreciably and also causes it to lose large amounts of heat before its temperature decreases significantly causing temperature moderation. 2.Eg. HIgh heat capacity helps organisms maintain a constant body temperature. D. High specific heat of vaporization 1.Explanation: Hydrogen bonding causes liquid H2O to absorb a large amount of heat to become a vapour(gas) and causes evaporative cooling. 2.Eg. May organisms including humans dissipate body heat by evaporation of H2O from surfaces, such as skin(by sweating) and tongue(by panting) E. Expansion of water upon freezing 1.Highest density of water at 4 degrees Celsius Explanation: AS H2O molecules cool below 0 degrees C, they form a crystalline lattice (freezing). The hydrogen bonds between the V-shaped molecules spread the molecules apart, reducing the density below that of liquid water causing ice to float on water. 2.The expansion upon freezing comes from the fact that water crystallizes into an open hexagonal form. This hexagonal lattice contains more space than the liquid state. F. Versatility as a solvent 1.it is able to dissolve many substances due to its polarity