Presentation on theme: "Safety ! Chem-Lab is a place where hazards occur:"— Presentation transcript:
Chem-Lab is a place where hazards occur:
To avoid that, follow instructions: Always wear safety eye glasses when in the laboratory
Beware of hot glass, Watch for small chips and cracks on glassware.
All books, coats, and other personal effects should remain separate from the experiment area.
Do not touch, taste, or smell chemicals unless directed to do so. Read labels carefully, don't use chemicals with no labels.
pour acids slowly and carefully, Never add water to acids.
Wear gloves when handling caustic chemicals.
Physical character Condition حالة المادة color Solubility miscibility odor
Physical Properties: 1-Condition : Solid: A- Crystalline it has a definite shape may be : Needles, Prisms, Plates, Microcrystalline B- Powder may be Fine or Coarse C-Amorphous (has no definite shape)
Solid - crystalline- prisms
Solid- crystalline- needles
Solid –crystalline- microcrystals
Solid- crystalline- pills
Solid – crystalline-plates
Solid – powder- (coarse or fine)
Liquid: A- Mobile (such as : methanol, ethanol) B- Viscous (such as lactic acid, glycerol)
Physical Properties: 2-Color : Note and describe the color of the sample weather its liquid or solid.
Why are some compounds colored? The colour is due to the presence of Chromophore group (causes extended conjugation) Examples of chromophoric groups : NO2, COOH
Some of expected colours: ColourExpected substance BrownHigher aromatic amines PinkNaphthols Colourless turns brown due to air oxidation Phenols, aniline, aminophenols Colourless turns to yellowAnthracene, cinnamic acid
3-odour Physical properties: 3-odour if no odor odorless OdorExpected substance Bitter almondBenzaldehyde, nitrobenzene Mice like odouracetamide Pleasant sweety odourEsters-chloroform Vinegar like odourAcetic acid Fishy odourAniline Pungent (irritant odour)Formaldehyde, lower acids Stable like odourP-toluidine Apple like odorethyl acetate Phenolic odorMany phenols
4-solubility/miscibility: Physical properties: 4-solubility/miscibility: First you need to note the following: Solubility is for solids and we say soluble in. Miscibility is for liquids and we say miscible with.
miscibility with H2O:
PURIFICATION OF ORGANIC COMPOUNDS Crystallization is : The process in which a solid substance separates from saturated solution as crystals. It is a technique which used to purify solid compounds, based on solubility and depends on : 1) Dissolving organic compounds (solutes) in hot liquids ( solvents ) 2) Filtration to remove impurities. 3) Cooling the hot solution to precipitate the organic compounds in crystal form
RECRYSTALLIZATION Recrystallization used to purify solids based on their different solubilities. Recrystallization Steps: 1- Add a small quantity of appropriate solvent to an impure solid. 2- Apply heat to dissolve the solid. 3- Cool the solution to crystallize the product. 4- Use vacuum filtration to isolate and dry the purified solid.
Sublimation Sublimation is : " The transition of a substance from the solid phase to the gas phase without passing through ansolidgas intermediate l iquid phase ".l iquid solid↔ vapor Examples: Carbon dioxide Iodine Naphthalene Naphthalene,
PURIFICATION OF LIQUID ORGANIC COMPOUNDS Distillation Distillation is the process of heating a liquid until it boils, capturing and cooling the resultant hot vapors, and collecting the condensed vapors. Distillation is used for both identification and purification of organic compounds. Types of Distillation 1- Simple distillation Purification of organic compounds from a non volatile impurities eg, (solid material)
Simple Distillation Simple distillation is designed to evaporate a volatile liquid from a solution of non- volatile substances; the vapor is then condensed in the water condenser and collected in the receiver.
2-Fractional Distillations Mixtures of liquids whose boiling points are similar (separated by less than 70°C) cannot be separated by a single simple distillation.In these situations, a fractional distillation is used. 3-Steam Distillation Distillation of 2-immiscible liquids, this technique can be used for purification of high boiling liquids which decompose near their boiling points and these liquids are immiscible with water
Fractional and Steam Distillation
3- Vacuum Distillation IT is used to distill compounds that have a high boiling point or any compound which might undergo decomposition on heating at atmospheric pressure. The vacuum is provided either by a water aspirator or by a mechanical pump.
EXTRACTION WITH SOLVENTS Extraction : Separation and isolation of organic substances from the mixtures, it can be subdivided into : 1- Extraction of Solids: e.g. perfume essence from flowers by using solvents ( H2O, CHCL3 )
2- Extraction of Solutions : Technique used for isolation dissolved substances by shaking its solution with immiscible solvent in a separatory funnel. On standing, the two immiscible phases (usually organic and aqueous) from two separate layer ( upper and lower) that can be separated by a means of a separatory funnel
CHROMATOGRAPHY 1- Thin Layer Chromatography – TLC is a simple, quick, and inexpensive procedure that gives a quick answer to how many components are in a mixture.
2- Column Chromatography column chromatography a purification technique used to isolates desired compounds from a mixture. The stationary phase, a solid adsorbent, is placed in a vertical glass (usually) column and the mobile phase, a liquid, is added to the top and flows down through the column (by either gravity or external pressure).
1- Melting Points The temperature at which the solid phase is in equilibrium with the liquid phase for the given substance, or the temperature at which the solid and liquid have the same vapour pressure ( solid ↔ liquid )
Mixed melting points can be used in the following manner to determine whether two compounds are the same or different even they have similar melting points. Assuming that a given organic (A) melts sharply at 120 C, and benzoic acid (compound B) also has melting point at 120 C. Is compound (A) benzoic acid or different compound?
If compound (A) is benzoic acid, then a mixed melting point of (A) and (B) will melt sharply at 120 C, i.e. the same as each individual compound alone. If, on the other hand, compound(A)is not benzoic acid, then the melting point of a mixture of (A) and (B) will be lowered and the melting range will be broadened. Since they are different compounds, each behaves as an impurity in the other.
2- Boiling Point The boiling point is the temperature at which the vapor pressure of the liquid phase of a compound equals the external pressure acting on the surface of the liquid. The external pressure is usually the atmospheric pressure.
Experimental Objective : Crystallization of Benzoic acid Glass ware : 2 conical flask, funnel, beaker, glass rod, stand, wire gauze, clamp.filter paper. Chemicals : Benzoic acid, distilled water Procedure : 1- Place 2gm of Benzoic acid in a 100ml conical flask 2- heat 50ml of distilled water to boiling 3- add the water to the benzoic acid until it dissolve completely using glass rod 4- prepare a fluted filter paper and short –stem funnel, place it in a suitable conical flask and start to filtrate the hot solution rapidly. 5- leave the filtrate to cool at room temperature 6- filter the cold solution and collect the pure crystals.
Experimental Objective : Separating a two-liquid component Glass ware : separatory funnel, 2 conical flask,stand, wire gauze, clamp holder, filter paper. Chemicals : Ether,water \ Procedure Place 50ml of water and 50ml of ether in a separating funnel Shake it well Draw off the lower aqueous layer into a flask and repeat extraction of the lower phase Draw off the other layer into another flask.