Chemistry syllabus notes

1 1. Experimental Chemistry 1.1 Experimental Design (a) name appropriate apparatus for the measurement of time, temperature, mass and volume; including burettes, pipettes, measuring cylinders and gas syringes Time: stopwatch (s), Mass: Electronic balance (kg, g), Temperature: Alcohol thermometer (k), Volume: Pipette (accurate volume 10.0cm3), Volumetric flask (large accurate volume 100cm3), Measuring cylinder (nearest 0.5cm3), Burette (nearest 0.05cm3) (b) suggest suitable apparatus, given relevant information, for a variety of simple experiments, including drying and collection of gases and measurement of rates of reaction Water displacement: Insoluble/slightly soluble (h2, o2, co2), Downward delivery: Denser than air (cl2, hcl, so2). Upward delivery: Less dense than air (nh3) Concentrated sulfuric acid: Remove water from acidic gas, Quicklime [freshly heated before use]: Remove water from alkaline gas, Calcium chloride [freshly heated before use]: Neutral gas (neither acidic nor alkaline) 1.2 Methods of Purification and Analysis (a) describe methods of separation and purification for the components of mixtures, to include: (i) use of a suitable solvent, filtration and crystallization or evaporation Use of suitable solvent: Separate solids of different solubility (s-s mixture, only one solid is soluble in solvent used) Filtration: Separate insoluble solids from liquids (Passes through filter paper is filtrate, remains on filter paper is residue) Crystallization: If solute is easily decomposed, this method is used. Obtaining pure solid from saturated solution. (saturated is when no more solute can be dissolved.) Cool saturated solution until crystals appear. Pour mixture to funnel to collect crystals. Crystals are washed with cold water to remove impurities and dried between 2 sheets of filter paper. Evaporation: Heat cause water to be evaporated, leaving salt behind. Substance with lower bp will turn into gas first, leaving another behind. Heat the solute till a solid is left behind. (ii) Sublimation Sublimation: Separate a substance that changes from solid to gaseous state directly. (iii) distillation and fractional distillation (see also 11.1(b)) Distillation: Separate pure solvent from a solution. Relies on the diff in bp (l-g) Salt water heated and vapor rises through the condenser and exit to the conical flask. Water vapor cools in the condenser and condenses back to the liquid. Pure water is collected as distillate. As more water vaporizes, the salt concentration gets more concentrated and a solid residue remains in the distillation flask . Boiling chips: Smooth boiling Fractional distillation: Separate miscible liquids with diff bp. When solution is heated, both ethanol and water vapor rises and the water with a higher bp will condense on the cool surface of the fractionating column and returns back to the liquid. Hot ethanol will cool and condense into liquid in the condenser and flow