Chapter 28: Q16P (page 791)
Referring to Table 28-7, explain how an anion-exchange resin can be used for absorption and analysis of \({\bf{S}}{{\bf{O}}_2}\)released by combustion.
\({\rm{SO}}_3^{2 - }\) is oxidized to \({\rm{SO}}_4^{2 - }\) by\({{\rm{H}}_2}{{\rm{O}}_2}\). The sulfate is measured by ion chromatography.
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By what factor must the mass increase to reduce the sampling standard deviation by a factor of 2?
EXAMPLE- Particles designated \(50/00\)mesh pass through a 50 mesh sieve bou are retained by a lo0 mesh sieve. Their size is in the range 0.150-0.300 mm.
does not pass is retained for your sample. This procedure gives particles whose diameters are in the range \(0.85 - 1.18\;{\rm{mm}}.\) We refer to the size range as \(16/20{\rm{mesh}}.\)
Suppose that much finer particles of \(80/120\)mesh size (average diameter \( = 152\mu {\rm{m}},\) average volume\( = 1.84\;{\rm{nL}}\)) were used instead. Now the mass containing \({10^4}\) particles is reduced from \(11.0to0.0388\;{\rm{g}}.\) We could analyze a larger sample to reduce the sampling uncertainty for chloride.
Question: Consider a random mixture containing \(4.00\;{\rm{g}}\)of \({\rm{N}}{{\rm{a}}_2}{\rm{C}}{{\rm{O}}_3}\) (density\(2.532g/mL\)) and \(96.00\;{\rm{g}}\)of \({{\rm{K}}_2}{\rm{C}}{{\rm{O}}_3}\) (density\(2.428\;{\rm{g}}/{\rm{mL}}\)) with a uniform spherical particle radius of\(0.075\;{\rm{mm}}\).
(a) Calculate the mass of a single particle of \({\rm{N}}{{\rm{a}}_2}{\rm{C}}{{\rm{O}}_3}\) and the number of particles of \({\rm{N}}{{\rm{a}}_2}{\rm{C}}{{\rm{O}}_3}\) in the mixture. Do the same for\({{\rm{K}}_2}{\rm{C}}{{\rm{O}}_3}\).
(b) What is the expected number of particles in \(0.100\;{\rm{g}}\)of the mixture?
(c) Calculate the relative sampling standard deviation in the number of particles of each type in a \(0.100\;{\rm{g}}\)sample of the mixture.
Barbital can be isolated from urine by solid-phase extraction with\({{\bf{C}}_{18}} - \)silica. The barbital is then eluted with\({\bf{1}}:{\bf{1}}\) vol/volacetone: chloroform. Explain how this procedure works.
Barium titanate, a ceramic used in electronics, was analyzed by the following procedure: Into a Pt crucible was placed \(1.2\;{\rm{g}}\)of \({\rm{N}}{{\rm{a}}_2}{\rm{C}}{{\rm{O}}_3}\) and \(0.8\;{\rm{g}}\)of \({\rm{N}}{{\rm{a}}_2}\;{{\rm{B}}_4}{{\rm{O}}_7}\)plus \(0.3146\;{\rm{g}}\)of unknown. After fusion at \({1000^\circ }{\rm{C}}\)in a furnace for\(30\;{\rm{min}}\), the cooled solid was extracted with \(50\;{\rm{mL}}\)of\(6{\rm{MHCl}}\), transferred to a \(100 - {\rm{mL}}\) volumetric flask, and diluted to the mark. A \(25.00 - {\rm{mL}}\)aliquot was treated with \(5\;{\rm{mL}}\)of \(15\% \)tartaric acid (which complexes \({\rm{T}}{{\rm{i}}^{4 + }}\)and keeps it in aqueous solution) and \(25\;{\rm{mL}}\)of ammonia buffer,\({\rm{pH}}9.5\). The solution was treated with organic reagents that complex\({\rm{B}}{{\rm{a}}^{2 + }}\), and the \({\rm{Ba}}\)complex was extracted into \({\rm{CC}}{{\rm{l}}_4}.\)After acidification (to release the \({\rm{B}}{{\rm{a}}^{2 + }}\) from its organic complex), the \({\rm{B}}{{\rm{a}}^{2 + }}\)was backextracted into\(0.1{\rm{MHCl}}\). The final aqueous sample was treated with ammonia buffer and methylthymol blue (a metal ion indicator) and titrated with \(32.49\;{\rm{mL}}\) of \(0.01144{\rm{M}}\)EDTA. Find the weight per cent of Ba in the ceramic.
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