# Weighing the sampleForming a precipitateFiltering the solutionWeighing the dry precipitate This analytical technique includes: Empirical formula and Molecular.

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Weighing the sampleForming a precipitateFiltering the solutionWeighing the dry precipitate This analytical technique includes: Empirical formula and Molecular formula Gas equations Eg. Pv=nrt Percentage of water/ measuring water content Limiting and Excess reactant equations Precipitation reactions Key steps in a precipitation reaction- what this looks like

#1: Accurately weigh the mixture to be analysed. #4: Filter off the precipitate and wash it with a small quantity of substance. #2: Dissolve the mixture in a suitable solvent; filter off and discard any insoluble material. #3: Add an excess amount of solution, that will form a precipitate with the substance being analysed. #5: Dry the precipitate and, cool and accurately weigh. Repeat until a constant mass is achieved.

Gravimetric analysis is a technique through which the amount of an analyte (the ion being analyzed) can be determined through the measurement of mass. Gravimetric analysis depend on comparing the masses of two compounds containing the analyte. http://www.youtube.com/watch?v=g6nXg zjW7nw&feature=related

Advantages Precise measurement/ high degree of accuracy (6-figure) Helps in determination of atomic mass, of elements Doesnt require a series of standards to calibrate the unknown solution concentration Helps in calibration of other instruments Disadvantages Limited group of elemental analysis Convoluted methods Only suitable for high concentrations

Gravimetric analytical data is interpreted from the weighing of the precipitate at the end of the experiment. To do this, you must weigh the instrument in which the precipitate will be weighed in, note the weight, and then weigh the precipitate. The solid weight is determined by the difference between the two.

Calibration is predominantly undertaken by gravimetric analysis and is the method most commonly used by laboratories accredited to ISO17025. There are colorimetric methods in use and these are often used for checking pipettes and for non-accredited calibration. Gravimetric analysis is preferred due to the simplicity and the traceability to an absolute standard. Gravimetric methods are also often recognsied as a more economical way of calibration. Gravimetric analysis for pipette calibration entails dispensing samples of distilled water into a receiving vessel in a precision analytical balance. The density of water is a known constant, the temperature, barometric pressure and humidity are recorded (the Z-factor used in the final mass calculation) and kept within certain limits and thus the mass of the dispensed sample provides an accurate indication of the volume dispensed.

Determination of atomic mass of elements Purity evaluation Determining water content of complex materials. Eg. Food and soil Treating ore (part of earths layer)

Geomarine survey systems A chunk of ore is treated with concentrated nitric acid and potassium chlorate to convert all of the sulfur to sulfate. The nitrate and chlorate are removed by treating the solution with concentrated HCl. The sulfate is precipitated with Barium and weighed as BaSo4. Monitoring the air Sulfate with nitrate and chlorate Concentrated HCl to remove nitrate and chlorate BaSO4

Gravimetric analysis obtains more accurate data about the composition of a sample than volumetric analysis does, however it takes longer to perform in the laboratory. Gravimetric analysis is analysis by weight, where as volumetric analysis is by volume. Gravimetric analysis is less sensitive to temperature than volumetric analysis is. volumetric Gravimetric- less sensitive Temp. Gravimetric-weight Volumetric- volume

Looks like a titration/ same as Measure from bottom of meniscus Wherever there is a concentration of a known solution, to be found, then volumetric analysis is the method to use. Quantative analytical technique Measure from bottom of meniscus Titration/ volumetric analysis

Equipment

Advantages Fast and easy to perform Only basic laboratory equipment needed Very cheap Accurate results Different methods available for different substances Disadvantages Relatively large sample size needed Only suitable for relatively high concentrations

Data is interpreted by using three concordant titres. These help to give accurate results and need to be within 0.1 of each other. Concordant titres- they should all be a similar colour

To ensure proper measurement of large volumes in the laboratory, volumetric apparatus should be calibrated regularly. Two of the most common apparatus calibrated are volumetric flasks and serological pipettes. *If the error is more than 0.03% then the apparatus should be discarded or changed into a volumetric apparatus Manual procedure via volumetric flask - Weigh the volumetric flask. - Fill the volumetric flask with distilled water, up to the mark - Weigh the volume of distilled water contained in the flask. - Calculate the true volume of glassware via the formula - Record the data - Do the same procedure with the serological pipette. - Record again your data.

Used in bio diesel manufacture to ensure that the mix has a neutral pH. To determine the amount of acetic acid in manufactured vinegar. To determine fatty-acid content and unsaturated-fatty acid content. Brain imaging and MR imaging, as well as routine clinical use. Suitable for direct titrations Suitable in Determination of iron Manufactured vinegar brain imaging

Compared to other analysis; for example gravimetric analysis, volumetric analysis is less accurate and less reliable. In volumetric analysis, you are more likely to encounter limits of sensitivity in volume measurements, compared to other analytical techniques. A mass is generally easier to determine and standardize than a concentration. Errors associated with volume measurements are minimized in other analytical techniques, such as gravimetric analysis. Volumetric analysis less accurate

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