Gravimetric Analysis What is gravimetric analysis How the

Gravimetric Analysis

What is gravimetric analysis?

How the technique works….

An example of gravimetric analysis The procedure to calculate the % Na. Cl in a sample is fairly straight forward. In this process: - a known mass of foodstuff is diluted with water to dissolve all the Na. Cl - the dissolved Na. Cl is then separated from the rest of the foodstuff by filtering - the Cl- ions (in the filtrate) are precipitated by reacting them with Ag. NO 3 (forming insoluble Ag. Cl) - filtering this precipitate and drying then leaves solid - dry Ag. Cl which is weighed. - from the mass the number of mole of Ag. Cl can be determined and hence the number of mole of Na. Cl in the foodstuff and then the mass of Na. Cl.

The % by mass of many ions and ionic compounds can be determined using this precipitation method as long as the: - ppt has a known formula - ppt has very low solubility - ppt is stable when heated

Solubility It is important that the specific ion doesn't form precipitates with other ions which may be present. This means you will need to be confident in identifying spectator ions and producing ionic equations. element ppt name chlorine Ag. Cl silver chloride bromine Ag. Br silver bromide iodine Ag. I silver iodide iron Fe 2 O 3 iron (III) oxide phosphorus Mg 2 P 2 O 7 magnesium pyrophosphate magnesium Mg 2 P 2 O 7 sulfur Ba. SO 4 barium sulfate Sources of Error - What are the potential sources of error in a typical analysis?