Methods of Separating Mixtures PDF

The pure substances that make up mixtures can be separated via physical means. This is because they have not formed new compounds. Separation methods utilised depend on: the physical properties of the components in the mixture which component is desired from the mixture Paper Chromatography Filtra...

The pure substances that make up mixtures can be separated via physical means. This is because they have not formed new compounds. Separation methods utilised depend on: the physical properties of the components in the mixture which component is desired from the mixture Paper Chromatography Filtration Crystallization Decanting Distillation Methods of Separating Mixtures Paper Chromatography The physical property used that allows for separation here is solubility (in different mediums). Paper chromatography is used to separate and identify different pigments found in inks and dyes. During the process, the solvent travels up the paper and the pigments dissolve in it once it reaches the origin line. Paper Chromatography Separation then occurs via the preference of the pigments: If the pigment is more soluble in the paper medium, it travels up the paper slower. If the pigment is more soluble in the solvent medium, it travels up the paper faster. The distance travelled is a good indicator of the pigment’s solubility in the mediums. Filtration - contains holes large enough for only the liquid to pass through (insoluble solid) (liquid) Particle size is the physical property which allows for separation with this method. Filtration is generally used to separate suspensions where either the solid (insoluble compound), the liquid or both are desired from the suspension. Decanting The physical property used for separation here is density. The component usually desired for collection is a solvent. The solvent can come from the liquid portion of suspension. a suspension with two distinct layers seen over time. Due to gravity, the more dense component settles to the bottom. liquid is guided into the collection container, reducing the chance of spilling. less dense substance (liquid) is poured off and collected in a separate container. Decanting The solvent desired can also be one of two (or more) immiscible liquids in a mixture. Separating funnel less dense liquid more dense liquid conical flask a suspension of two immiscible liquids oil and water Separating funnel Crystallization The physical property which allows for separation is boiling point. This method allows for the separation of a soluble solid from a solution Distillation The physical property that allows for separation is boiling point. The desired component is at least one (or more) solvent(s). There are two types of distillation. Simple Distillation Fractional Distillation Simple Distillation This is done to separate the contents of a solution, where the desired component for collection is either the solvent or both the soluble solid and the solvent (liquid). For the process to work, the mixture is heated to the boiling point (temperature) of the solvent. This allows the solvent to vaporise. Simple Distillation The vapor of the solvent rises, exits via the sidearm and flows into the condenser. The thermometer measures the temperature of the vapour. If it remains constant, the vapour is pure. The condenser cools the vapour as it flows down using cold water which enters at the bottom section, flowing up and out of the condenser in the top section. Simple Distillation The vapour cools as it flows down the condenser and condenses into a liquid. This liquid is collected in a container placed at the end of the condenser. It is known as the distillate. The process continues until all the solvent is removed from the distilling flask and the solid remains. Fractional Distillation This is used separate a mixture of two or more miscible liquids. Usually, the boiling points are relatively close for the liquids present, therefore a fractionating column is inserted in the apparatus used for simple distillation. As the mixture boils, vapors of the liquids present move into the fractionating column, where they will condense and vaporize over the beads present many times. Fractional Distillation Over time, the more volatile solvent (the one with the lower boiling point) dominates the vapors at the top of the column. This is proven by the thermometer having a constant temperature, that of the more volatile solvent’s boiling point. The vapors of the more volatile solvent moves into the condenser, while the other liquids condense in the fractionating column and return to the distilling flask. Fractional Distillation The vapors that have moved into the condenser are converted into a liquid and are collected as distillate A (1st liquid). When majority of that liquid has been collected, the temperature will start to rise, indicating that the vapors are no longer pure. The collecting container is removed and a mixture of liquids is collected next until the temperature reaches a constant temperature again. Fractional Distillation This new constant temperature is the boiling point of the second solvent so a new receiving flask is used and a pure distillate of that liquid can be collected. This process continues until all the solvents have been obtained.