11 Questions
What is the term used to describe a chemical that causes a solid to form in a liquid solution?
Precipitant
What is the primary difference between classical analysis and instrumental analysis?
Use of no instruments other than a balance
What is the term used to describe the solid formed in a liquid solution?
Precipitate
What is the requirement for a precipitate to form in a solution?
The concentration of the ions must be above the solubility product
What is the primary characteristic of gravimetric analysis?
It relies on a critical mass measurement
What is the term used to describe the process of separating a solid from a liquid solution using a centrifuge?
Centrifugation
What process involves the formation of a solid from a solution?
Precipitation
Which type of precipitate is characterized by a jelly-like, hydrous mass that traps a great deal of water and impurities?
Gelatinous
What is a common characteristic of crystalline precipitates?
They have a well-defined structure
Which type of precipitate is composed of aggregates of small, porous particles?
Curdy
What is the primary difference between gelatinous and curdy precipitates?
Their filterability
Study Notes
Categories of Chemical Analysis
- Chemical analysis is divided into two categories: classical analysis and instrumental analysis
- Classical analysis, also known as wet chemical analysis, uses no mechanical or electronic instruments other than a balance
- Instrumental analysis involves the use of an instrument, other than a balance, to perform the analysis
Gravimetric and Volumetric Analysis
- Both classical and instrumental quantitative analysis can be divided into gravimetric and volumetric analysis
- Gravimetric analysis relies on a critical mass measurement
- Volumetric analysis involves the measurement of the volume of a solution whose concentration is known and applied to determine the concentration of the analyte
Precipitation Reactions
- Precipitation occurs when two soluble compounds containing ions that form an insoluble liquid are mixed in solution
- A precipitate will form only if the instantaneous concentrations of the ions upon mixing exceed the solubility product of the insoluble substance
- A precipitant is a chemical that causes a solid to form in a liquid solution
- The solid that is formed is called the precipitate
Recovering a Precipitate
- Methods for recovering a precipitate include filtration, centrifugation, and decantation
Types of Precipitates
- Crystalline precipitates: have well-defined/regularly shaped crystals whose shapes are a function of the composition of the salt
- Examples of crystalline precipitates include calcium oxalate and the alkaline earth sulfates such as barium sulfate
- Gelatinous precipitates: are flocculated colloids; jelly-like, hydrous masses that trap a great deal of water and many impurities
- Examples of gelatinous precipitates include metal hydroxides such as ferric hydroxide
- Curdy precipitates: are aggregates of small porous particles that can be filtered rapidly, easily, and completely
- Examples of curdy precipitates include the silver halides compounds
Learn about the two categories of chemical analysis, including precipitation reactions. Understand the difference between a precipitate and a precipitant, and how to recover a precipitate using methods like filtration and centrifugation.
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