Skoog Análise Instrumental Resolução Chapter 35 solutions

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Fundamentals of Analytical Chemistry: 8
th
 ed. Chapter 35 
Chapter 35 
35-1 Invalid sampling, loss of sample during weighing or dissolution, contamination by 
impurities in reagents, and changes in composition due to varying moisture content. 
35-2 (a) Sorbed water is that held as a condensed liquid phase in the capillaries of a colloid. 
Adsorbed water is that retained by adsorption on the surface of a finely ground solid. 
Occluded water is that held in cavities distribute irregularly throughout a crystalline solid. 
(b) Water of crystallization is the water contained in a stable solid hydrate, such as 
BaCl22H2O. Water of constitution is water that is released from certain compounds 
when they are heated or otherwise dehydrated. For example 
 Ba(OH)2(s)  BaO(s) + H2O 
(c) Essential water is chemically bound water that occurs as an integral part of the 
molecular or crystalline structure of a compound in its solid state. Nonessential water is 
that retained by a solid as a consequence of physical forces. 
(d) A gross sample is a replica of the entire mass of material to be analyzed. It 
corresponds to the entire sample in both average chemical composition and also in 
particle size distribution. The laboratory sample is a homogeneous material whose 
chemical composition mimics that of the gross sample and, therefore, the population. 
35-3 The particle size of a sample should be reduced before preparing a sample for laboratory 
analysis in order to obtain a homogeneous laboratory sample representative of the gross 
sample. 
Fundamentals of Analytical Chemistry: 8
th
 ed. Chapter 35 
35-4 Losses of volatile components as a result of heating, reaction with the atmosphere, 
changes in water content, losses as dust, and contamination due to mechanical wear and 
abrasion of the grinding surfaces.