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What is precipitation in chemistry
The process of forming a solid (precipitate) from a solution due to exceeding solubility product (Ksp)
Define solubility product (Ksp).
The equilibrium constant for the dissolution of a solid in a solution.
What is the common ion effect?
A reduction in solubility of a salt due to the presence of a common ion.
What happens when Ag+ is added to a saturated solution of AgCl?
AgCl precipitates to maintain the Ksp equilibrium.
How is the pH of a saturated solution of Ca(OH)2 determined?
From the concentration of OH- ions, calculated using Ksp.
What affects the solubility of Ca(OH)2 in water?
Increasing pH decreases solubility due to the common ion effect; lowering pH increases solubility.
What is Mohr’s method?
A direct titration method using AgNO3 and K2CrO4 as an indicator to detect halides.
What is the endpoint in Volhard’s back titration?
Formation of a deep red color using ammonium iron (III) sulfate as an indicator
What is a complex ion
A central metal ion bonded to ligands through coordinate covalent bonds
What are chelating agents?
Ligands that can form multiple bonds with a central metal ion, e.g., EDTA
Give an example of a bidentate ligand.
Ethylenediamine (H2N-CH2-CH2-NH2).
What is the coordination number?
The number of donor atoms bonded to a central metal ion in a complex.
What is EDTA, and what is its use?
A chelating agent used in metal ion titrations and to treat heavy metal poisoning
How does EDTA remove metals in titration?
By forming stable complexes with polyvalent metal cations.
Define oxidation and reduction.
Oxidation is the loss of electrons, and reduction is the gain of electrons.
What is a reducing agent?
A substance that donates electrons and gets oxidized in the process
Write the reaction for the oxidation of MnO4-.
MnO4− + 8H+ +5e− →Mn2+ + 4H2O.MnO4- + 8H+ + 5e- → Mn2+ + 4H2O
What is the color change in the assay of hydrogen peroxide with KMnO4?
From purple to colorless as MnO4−MnO4- is reduced.
What is the purpose of ferroin sulfate in Fe2+ assays?
It acts as an indicator, changing color from red (Fe2+) to blue (Fe3+).
What is an example of a redox assay?
The reaction of ascorbic acid with iodine to form dehydroascorbate.
How is KI titrated in a redox reaction?
Iodine is liberated and titrated with sodium thiosulfate using starch as an indicator
Why is pH important in EDTA titrations?
Complexes are most stable in alkaline solutions, so buffers are used.
How does the oxidation number affect complexation?
It determines the stability and stoichiometry of the complex.
How is the stability constant (Kf) calculated?
By the equilibrium concentration of the complex and its components.
Why is the common ion effect important in gravimetric analysis?
It reduces solubility, minimizing loss of the precipitate during washing.
What is an adsorption indicator?
A dye that adsorbs onto precipitate surfaces, signaling the endpoint of titration.
Give an example of an adsorption indicator.
Fluorescein, which forms a pink complex with Ag+ ions at the endpoint.
Why is starch used in iodometric titrations?
It forms a blue complex with iodine, making the endpoint easier to detect.
How does a pH indicator function in EDTA titrations?
It changes color to signal metal ion complexation.
