Lesson 7: Precipitation and Volatilizatio Gravimetry
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A substance that is dissolved in a solution
Solute
the liquid in which asoluteisdissolvedto form a solution.
Solvent
a solution that contains less than the maximum amount of solute that is capable of being dissolved
Unsaturated Solution
a solution that has dissolved as much solute as it is capable of dissolving
Saturated Solution
interaction between solute and solution that forms ionic bond or precipitate
Precipitate Forms
a solution that contains more than the maximum amount of solute that is capable of being dissolved at a given temperature.
Supersaturated Solution
an Unstable solution that contains a higher solute concentration than a saturated solution
supersaturated solution
a quantitative method that is based on determining the mass of a pure compound to which the analyte is chemically related. It is based on mass measurements with an analytical balance
Gravimetric Methods
the analyte is separated from a solution of the sample as a precipitate and is converted to a compound of known composition that can be weighed.
Precipitation Gravimetry
the method in which the analyte is converted to a soluble precipitate
Precipitation Gravimetry
can be obtained by filtering, washing free of impurities, converting to a product of known composition by suitable heat treatment, and weighing.
precipitate
What are the 4 properties of precipitating agents
(1) easily filtered and can be washed free of contaminants (2) of sufficiently low solubility that no significant loss of the analyte occurs during filtration and washing; (3) Chemical inert or is unreactive with the constituents of the open atmosphere; (4) Composition can be determined with high confidence after it was dried or ignited.
a few ions, atoms, or molecules (around four or five) come together to form a stable solid. Often, these nuclei form on the surface of suspended solid contaminants, such as dust particles.
Nucleation
two ways at which precipitates are formed
Nucleation and particle growth
If predominates, a precipitate containing a large number of small particles results
nucleation
if predominates, a smaller number of larger particles is produced.
particle growth
competition between additional nucleation and growth of existing nuclei
particle growth
minimum number of atoms, ions, or molecules join together to give a stable solid
Nucleation
As excess solute precipitates with time, supersaturation decreases to zero
supersaturated solution
coagulation of colloids can be hastened by what methods?
• Heating • continuously stirring • by adding an electrolyte into the mixture that will act as a medium
What is the reason for the stability of colloidal particles?
its particles are either positively or negatively charged and thus repel one another.
a process in which a substance (gas, liquid, or solid) is held on the surface of a solid.
adsorption
retention of a substance within the pores of a solid.
absorption
random movement of solute in solution
Brownian Motion