Normality and equivalents

One change that will be evident to many chemists is the deletion of normalities and equivalents from the body of the text. This has been done because current teaching and all our external contacts indicated that there was little long-term benefit in retaining them. However, there are many older readers who still employ this system and because of this we have retained a detailed explanation of normalities and equivalents as an Appendix. 

If normality and equivalents are used, we calculate equivalents of analyte as in Equation (4.25) (again, the substance titrated is the analyte) ... 

When dealing with normality and equivalents, it is not necessary to have balanced chemical equations on which to base your calculations. 

Throughout this text, we base volumetric calculations exclusively on molarity and molar masses. We have also included in Appendix 6 a discussion of how volumetric calculations are performed ba.sed on normality and equivalent weights because you may encounter these terms and their uses in the industrial and health science literature. 

Volumetric Calculations Using Normality and Equivalent Weight... 

Appendix 4 Formation Constants at 25°C A-10 Appendix 5 Standard and Formal Electrode Potentials A-12 Appendix 6 Use of Exponential Numbers and Logarithms A-15 Appendix 7 Volumetric Calculations Using Normality and Equivalent Weight A-19... 

Appendixes and Endpapers. Included in the appendixes are an updated guide to the literature of analytical chemistry, tables of chemical constants, electrode potentials, and recommended compounds for the preparation of standard materials sections on the use of logarithms and exponential notation, and on normality and equivalents (terms that are not used in the text itself) and a derivation of the propagation of error equations. The inside front and back covers of this book provide a full-color chart of chemical indicators, a table of molar masses of com-... 

Dimensional analysis is emphasized throughout to give you a better feel for the proper setting up of problems. SI units or symbols (e.g., L, mL, mol, and s) are used throughout. The concept of normality and equivalents is introduced, but emphasis remains on the use of molarity and moles. The presentation of normality is done in a way that allows it to be ignored if your instructor chooses not to assign it. 

To learn about normality and equivalent weight. To learn to use these concepts in stoichiometric calculations. 

Throughout the main text of this book standard solutions and quantities have all been expressed in terms of molarities, moles and relative molecular masses. However, there are still many chemists who have traditionally used what are known as normal solutions and equivalents as the basis for calculations, especially in titrimetry. Because of this it has been considered desirable to include this appendix defining the terms used and illustrating how they are employed in the various types of determinations. 

In aqueous solutions, concentrations are sometimes expressed in terms of normality (gram equivalents per liter), so that if C is concentration, then V = 103/C and a = 103 K/C. To calculate C, it is necessary to know the formula of the solute in solution. For example, a one molar solution of Fe2(S04)3 would contain 6 1CT3 equivalents cm-3. It is now clear as to why A is preferred. The derivation provided herein clearly brings out the fact that A is the measure of the electrolytic conductance of the ions which make up 1 g-equiv. of electrolyte of a particular concentration - thereby setting conductance measurements on a common basis. Sometimes the molar conductance am is preferred to the equivalent conductance this is the conductance of that volume of the electrolyte which contains one gram molecule (mole) of the ions taking part in the electrolysis and which is held between parallel electrodes 1 cm apart. 

If we apply this formula to defects in a crystal, and again assume that the defects are oppositely charged, so that they attract each other, the energy term will be roughly equivalent to the enthalpy of formation of a defect pair, AHp. The closest separation of the defects will normally be equivalent to the spacing between two adjacent lattice sites. 

C) H3PO4 is a triprotic acid that is, there are 3 moles of H+ ions produced for each mole of H3PO4 that completely ionizes. Normality is the number of equivalents per liter. Assuming complete or 100% ionization, a 1-molar HC1 solution is 1 normal. A 1-molar H2S04 solution is 2 normal, and a 1-molar solution of H3P04 is 3 normal. 

The titration error (i.e., difference between end-point and equivalence point) is found to be small when the potential change at the equivalence point is large. Invariably, in most of the reactions employed in potentiometric analysis, the titration error is normally quite small and hence may be neglected. 

Fig. 9-18. Band edge levels and equivalent Fermi levels of oxidative and reductive dissolution reactions of compound semiconductors in aqueous sohitions at pH 7 en ) - F(a

In particular, the techniques based on the termination of certain plies within the laminate has also shown promise. Static tensile tests of [30°/-30°/30°/90°]s carbon-epoxy laminates containing terminals of [90°] layers at the mid-plane show that premature delamination is completely suppressed with a remarkable 20% improvement in tensile strength, compared to those without a ply terminal. Cyclic fatigue on the same laminates confirms similar results in that the laminate without a ply terminal has delamination equivalent to about 40% of the laminate width after 2x10 cycles, whereas the laminates with a ply terminal exhibit no evidence of delamination even after 9x10 cycles. All these observations are in agreement with the substantially lower interlaminar normal and shear stresses for the latter laminates, as calculated from finite element analysis. A combination of the adhesive interleaf and the tapered layer end has also been explored by Llanos and Vizzini, (1992). 

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