8.7: Chapter Summary and Key Terms

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Chapter Summary

In a gravimetric analysis, a measurement of mass or a change in mass provides quantitative information about the analyte. The most common form of gravimetry uses a precipitation reaction to generate a product whose mass is proportional to the amount of analyte. In many cases the precipitate includes the analyte; however, an indirect analysis in which the analyte causes the precipitation of another compound also is possible. Precipitation gravimetric procedures must be carefully controlled to produce precipitates that are easy to filter, free from impurities, and of known stoichiometry.

In volatilization gravimetry, thermal or chemical energy decomposes the sample containing the analyte. The mass of residue that remains after decomposition, the mass of volatile products collected using a suitable trap, or a change in mass due to the loss of volatile material are all gravimetric measurements.

When the analyte is already present in a particulate form that is easy to separate from its matrix, then a particulate gravimetric analysis is feasible. Examples include the determination of dissolved solids and the determination of fat in foods.

Key Terms

coagulation

definitive technique

electrogravimetry

ignition

occlusion

precipitant
relative supersaturation

surface adsorbate

volatilization gravimetry

conservation of mass

digestion

gravimetry

inclusion

particulate gravimetry

precipitation gravimetry

reprecipitation

thermogram

coprecipitate

direct analysis

homogeneous precipitation

indirect analysis

peptization

quartz crystal microbalance

supernatant

thermogravimetry