Volumetric Analysis
Volumetric Analysis and Standard Solutions
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Purpose of Volumetric Analysis
Volumetric analysis is used for determining the concentration of a solution (with an unkown concentration). This is done by reacting the solution with a standard solution (solution of known concentration) and comparing volumes/moles to determine concentration.
Standard Solutions
Standard solutions are solutions of known concentration, they can be either primary or secondary standard solutions
Primary Standard Solutions
Primary standard solutions are prepared from a known quantity of a primary standar, they are made using a volumetric flask filled with water
Primary standards are pure substances
Criteria for a Primary Standard:
4 Characteristics:
1) Pure w/ a known formula
2) Soluble in water
3) Stable, meaning it does not:
react with itself (decompose) e.g. $\sf\small KMnO_4$
react with chemicals in the air e.g. $\sf\small NaOH
react with water, meaning it is not:
deliquescent (does not absorb moisture from the air) e.g. NaOH
hydroscopic () e.g. HCl
efflorescent e.g. Na ₂CO₃.10H₂O.
4) High molar mass (decreasing random error)⇒ weighing scale does not accurately or consistently show mass (rounds up/down)
This leaves 2 suitable compounds:
NaCO₃
H₂C₂O₄.2H₂O (the H₂O increases molar mass)
Secondary Standard Solution
⇒ Solution whose concentration is established by reacting it with a standard solution (”standardising”) Secondary Standards are obtained through titration