20 Questions
What is the primary focus of gravimetric methods of analysis?
Changing the phase of the analyte to separate it in its pure form
In gravimetric analysis, which method involves separation from a solution as a precipitate and conversion to a compound of known composition?
Precipitation method
What are the properties of gravimetric analysis?
Accurate, cheap, and simple to carry out
What does the mass of the product in electro-analytical method provide?
A measure of the analyte concentration
What experimental control can be used to achieve smaller particle size in a precipitate?
Precipitate from hot solution
Which factor influences the particle size of a precipitate?
Rate at which reactants are mixed
What type of suspension shows a tendency to settle spontaneously?
Crystalline suspension
What is the relationship between particle size and supersaturation during the precipitation process?
Inversely proportional
What is the first step in the precipitation gravimetric analysis?
Preparation of the solution
Why is it important for a gravimetric precipitating agent to be selective or specific?
To minimize the loss of analyte during filtration and washing
What is the role of dimethyl glyoxime (DMG) in precipitation gravimetric analysis?
To react specifically with Ni+2 ions
Why are precipitates consisting of large particles generally preferred for gravimetric work?
They are easier to filter and wash
What is the purpose of the digestion step in precipitation gravimetric analysis?
To convert the precipitate to a known product by suitable heat treatment
In precipitation gravimetric analysis, what causes essentially all of the calcium in the sample to precipitate as calcium oxalate?
Addition of oxalic acid and ammonia
How are small aggregates formed in nucleation during precipitate formation?
By coming together to form a stable solid
What are the two ways in which precipitates form in precipitation gravimetric analysis?
(1) By nucleation; (2) By particle growth
What properties should a good precipitate ideally possess?
Easy filtration and washing, free of contaminants, and known chemical composition after drying or igniting
What type of suspensions are formed when nucleation is faster than particle growth?
Colloidal suspensions
What determines the physical nature of precipitates formed by precipitation gravimetric analysis?
Relative rates of nucleation and particle growth
Why do we prefer precipitates consisting of large particles for gravimetric work?
They are easier to filter, wash, and are usually purer than those made up of fine particles.
Test your knowledge of gravimetric methods of analysis, which are quantitative techniques based on determining the mass of a pure compound related to the analyte. This quiz covers topics such as the determination of lead (Pb+2) in water and the process of precipitating compounds for analysis.
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