Analytical Chemistry: Assaying and Quality Control

Macro analysis deals with quantities of 10-1g or more.

A minor constituent is one present in the range 0.1-1 percent.

Submicro analysis deals with samples in the range 10-2g to 10-1g.

Assaying is a procedure to determine the composition of the final manufactured product.

A major constituent is one accounting for 0.01-100 per cent of the sample under investigation.

Ultramicro analysis deals with quantities above 10-4g.

The law of mass action states that the velocity of a chemical reaction is inverse to the product of the active masses of reacting substances.

CH3COOH is a strong electrolyte with an α value of 1.

At dynamic equilibrium, the forward and backward reaction velocities are not equal.

The Bronsted-Lowry theory discusses the role of solvent in the ionization process.

The equilibrium constant K is temperature-dependent.

A conjugate base is a base that accepts a proton.

ZnO is determined by treating it with a known excess of standard sodium hydroxide.

Ammonium chloride is added to avoid the precipitation of Ca(OH)2 in the determination of CaO.

Calcium carbonate is treated with a known excess of standard sodium hydroxide in the determination process.

Methyl red is used as an indicator in the determination of CaO.

The addition of ammonium chloride is necessary in the determination of CaO.

The total CaO/CaCO3 mixture can be determined by direct titration with standard acid.

If two weak acids have significantly different Ka values, they can be differentiated and two equivalence points will be obtained during titration.

H2SO4 is a diprotic acid that exhibits two distinct equivalence points during titration.

The pH of the first equivalence point of carbonic acid can be calculated using the formula pH = ½ pKw + ½ pKa - ½ pC.

Phosphoric acid is a diprotic acid with three distinct Ka values.

Carbonic acid can be directly titrated as a dibasic acid in the presence of phenolphthalein.

A mixture of acetic acid and propionic acid will titrate separately to give two distinct equivalence points.

The decomposition of potassium persulphate aqueous solutions is accelerated by boiling in the absence of silver ions.

The method of determining persulphate is suitable for ammonium persulphate.

The reaction of carbonyl compounds with hydroxyl amine hydrochloride leads to the formation of an oxime together with an equivalent quantity of free HCl.

The liberated acid in the determination of aldehydes and ketones is titrated with standard alkali using phenolphthalein as an indicator.

The dissolution of HgO in potassium iodide or potassium bromide solution produces an equivalent amount of acid.

About 20% of the volume of standard acid expected to be required in the titration is added before the addition of potassium iodide to minimize loss of ammonia.