Dilution problems

For economical reasons the fermentation time should be as short as possible with a high yield of the amino acid at the end. A second reason not to continue the fermentation in the late stationary phase is the appearance of contaminant-products, which are often difficult to get rid off during the recovery stage. In general, a relatively short lag phase helps to achieve this. The lag phase can be shortened by using a higher concentration of seed inoculum. The seed is produced by growing the production strain in flasks and smaller fermenters. The volume of the seed inoculum is limited, as a rule of tumb normally 10% of the fermentation volume, to prevent dilution problems. 

Ans. The sugar concentration is given by dividing the number of moles of sugar by the total volume. The moles of salt makes no difference in this problem because the problem does not ask about salt concentration and the salt does not react. This is simply a dilution problem for the sugar. 

E) In dilution problems, we use the formula M1V1 = M2V2 therefore, it is necessary to determine the molarity of the initial solution first. 

Many authors claim that the dilution by the sheath flow would not significantly affect the detection sensitivity, because it is completely evaporated in the spray process. Moreover, it has been discussed that in this layered-flow approach, preferably the inner layer of the spray enters the collector opening. If this were true, the composition of sheath liquid would be less important. Anyhow, it has to be stated that there is a dilution problem in the sheath-flow approach. In addition, it has been proven many times that ESI is a concentration-sensitive, not mass-sensitive, process. Knowing this, it makes sense to reduce the sheath liquid flow rate to the minimum required for stable spray conditions. 

Composition of solutions Concentrations expressed in physical units Concentrations expressed in chemical units Comparison of the concentration scales Summary of concentration units Dilution problems... 

Another approach to fraction collection is the use of an on-column frit structure or capillary fracture that depends on the electroosmotic flow to deposit the eluent in a continuous manner on a moving surface. Although this approach circumvents the dilution problem, the collection structures are complex and can result in the loss of some of the analyte. One commercially available fraction collection device couples CE with membrane fraction collection, without the need for frits or capillary fractures. The outlet vial holder can be removed and replaced with a wetted circular polyvinylidene difluoride (PVDF) disk, which enables the collection of eluted analytes and subsequent manipulations such as immunoblotting and microsequencing. Figure 6.13 shows a schematic diagram of the CE membrane fraction collector interface.74... 

The correct answer is (D). This is a dilution problem. In order to solve it, you need to use a modified version of the molarity equation. You know the molarity and the volume of the original solution, which means you can determine the number of moles of HC1 in the original 10.0 mL. This is done using the calculation ... 

Often solutions are prepared by dilution of more concentrated solutions of the same solute. (These dilution problems are similar to those involving molarity, presented in Chapter 11.) When we dilute a solution, the mass of the solute does not change, but the masses of the solvent and the solution do, and thus the percentage of each component changes. 

The most analytically unfavourable feature of DPHSE is that analytes are diluted in the liquid extract, which requires concentration (usually by static liquid-liquid or solid-phase extraction). However, the increased flexibility of DPHSE relative to ASE has been used to develop various approaches to the partial or complete automation of methods based on the use of hyphenated techniques. Such approaches not only allow the dilution problem to be overcome but also enable automation and/or facilitate the development of other steps of the analytical process such as filtration, detection or chromatographic separation. The principal approaches to automation and improved implementation of analytical steps subsequent to DPHSE are discussed below. 

For more practice with dilution problems, go to Supplemental Practice Problems in Appendix A. 

L.29 (a)MiFi = MiVi is used for calculation of dilution problems 1.00Lx0.50M ... 

In all dilution problems involving liquid solutions, it is almost always assumed that the final volume is equal to the volume of the initial solution plus the volume of the other solutions (or water) added. 

Many chemical reagents are supplied in solutions of much higher concentration than their use requires. The concentrated solutions need to be diluted with solvent to prepare solutions of lower concentration. Adding solvent increases the volume of the solution without changing the number of moles of solute, and the concentration of the solution decreases. For molar solutions, the volume of the solution in liters times the molarity of the solution equals the number of moles of solute. Because the number of moles of solute remains constant with dilution, a relationship in terms of volumes and molarities can be derived that is very useful for dilution problems. This is called the dilution equation. 

Comment An alternative approach to solving dilution problems uses the formula... 

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