Equivalent weight of acids

The saponiflcatlon equivalent or the equivalent weight of an ester is that weight in grams of the ester from which one equivalent weight of acid is obtainable by hydrolysis, or that quantity which reacts with one equivalent of alkali. The saponification equivalent is determined in practice by treating a known weight of the ester with a known quantity of caustic alkali used in excess. The residual alkali is then readily determined by titration of the reaction mixture with a standard acid. The amount of alkafi that has reacted with the ester is thus obtained the equivalent can then be readily calculated. 

Acids. Acidic oxides, acid anhydrides. Bases, basic oxides. Neutralization—hydrogen ion plus hydroxide ion. Hydronium ion. Equivalent weights of acids and bases. Normality. Monoprotic, diprotic, and triprotic acids. Monohy-droxic, dihydroxic, and trihydroxic bases. 

Gram-Equivalent Weight of Acid, Base and Salt... 

By the use of indicators - compounds which change colour as their environment changes from an acidic to a basic one (or vice versa) - the precise moment of neutralization can be determined. For example, a measured quantity of acid solution of unknown concentration is placed in a flask with an indicator (e.g. litmus). A solution of base of known concentration is run into the flask until, with the addition of one excess drop of base, the colour changes. The volume of base run in has been measured and it is now possible to calculate the concentration of the acid solution. The method of calculation can be found in any elementary chemistry book and depends on knowledge of the equivalent weights of acids and bases. Titrations are used in paint chemistry to determine the acid value of a resin (Chapter 12) and it will be seen from the definition of acid value that no knowledge of equivalent weights is required for this determination it is sufficient to know the concentration of the alkali solution. 

Quantitative results of a different kind were obtained by Jeremias Richter (1762-1807). He was obsessed with obtaining mathematical relationships in chemistry, and he helped to establish the concept of equivalent or combining weight. His work was summarised in 1802 by Ernst Fischer (1754-1831), who produced a table of equivalent weights of acids and bases related to sulphuric acid having a value of 1000. On this scale, muriatic acid (HCl) had a value of 712, and soda and potash had values of 859 and 1605 respectively. This meant that 859 parts of soda or 1605 parts of potash were required to neutralise 1000 parts of sulphuric acid or 712 parts of muriatic acid. 

Equivalent weights of acids and bases. One equivalent of an acid is the quantity that transfers (gives up) 1 mole ofH (1 mole of protons). Correspondingly, 1 eq of a base is the quantity that accepts 1 mole of H. Sodium hydroxide, NaOH, can react with phosphoric acid, H3PO4, for example, in any one of three ways ... 

In the second method. Stone et al. [84] copolymerized monomer 4-2 with TFS (Fig. 2.17) by emulsion polymerization in 21% isolated yield. The optimized ratio between TFS and the dimethyl phosphonate-substimted a,, -trifluorostyrene monomer in the copolymer 4-5 was 2.4 1. The molecular weights of the resulting copolymer were 38,100 and 105,900g/mol for and respectively. Homo-polymer 4-3 (membrane A) was hydrolyzed under acidic conditions (hydrochloric acid in dioxane, 100 °C, 20 h). The yield and the equivalent weight of acid functions were 95% and 130 g/mol, respectively. Copolymer 4-4 was hydrolyzed by the authors using two processes (i) basic conditions (potassium hydroxide, 84 °C, 64 h), membrane Cl, and (ii) acidic conditions with a DMF pretreatment, membrane C3. Finally, the authors concluded that the best results were obtained with an acidic hydrolysis and that membranes based on sulfonic acid-a,, -trifluorostyrene gave better results than those obtained from the phosphonic acid homolog. 

Equivalent weight of an acid. Determine the equivalent weight of the acid (use about 0 2 g.) by titration with standard ca. 0- N alkali... 

Equivalent Weights Acid-base titrations can be used to characterize the chemical and physical properties of matter. One simple example is the determination of the equivalent weighf of acids and bases. In this method, an accurately weighed sample of a pure acid or base is titrated to a well-defined equivalence point using a mono-protic strong acid or strong base. If we assume that the titration involves the transfer of n protons, then the moles of titrant needed to reach the equivalence point is given as... 

The lower equivalent weight of magnesium hydroxide compared to caustic soda, hydrated lime, and soda ash reduces the stoichiometric amounts necessary to neutralize a given amount of acid. Depending on relative alkah costs, magnesium hydroxide can offer the advantage of lower chemical costs. 

Apparent equivalent weight can be deterrnined by titration with hydrochloric acid using a bromocresol green indicator. Calculations give the equivalent weight of total amines and are not specific for the mono-, di- or tri alkan olamines. 

The tria2ine ring-containing product 1,3,5-triglycidyl isocyanurate (6) is synthesized by glycidylation of cyanuric acid with epichlorohydrin. The commercial product is a crystalline powder that exhibits an epoxy equivalent weight of ca 108 and softens in the 85—110°C range (see Cyanuric AND ISOCYANURIC acids). 

If acetal has been isolated, it may best be hydrolyzed by boiling with an equivalent weight of ethyl alcohol and concentrated hydrochloric acid (2 cc. for each 50 cc. of alcohol used) for four or five hours, then distillation of the ethyl alcohol, and treatment with water. 

Reductant equivalent weights of, 847 Reduction 409 by chromium(II) salts, 409 by hydrogen sulphide, 416 by Jones reductor (zinc amalgam), 410 by liquid amalgams, 412 by silver reductor, 414 by sulphurous acid, 416 by tin(II) chloride, 415 by titanium(II[), 410 by vanadium(II), 410 see also Iron(III), reduction of Reduction potentials 66 Reference electrodes potentials, (T) 554 Relative atomic masses (T) 819 Relative error 134 mean deviation, 134... 

One mole of HX is 25g 0.500mol of H2X2 is also 25g. You cannot tell from the mass which is the formula of the acid. In either case, the equivalent weight of the acid is 25g/cquivalent. The equivalent weight of H X2 is given by... 

EXAMPLE 15.14. Calculate the formula weight of an acid with three replaceable hydrogen ions and an equivalent weight of 20.1 g/equivalent. assuming complete neutralization. 

A sample of 4.00 g of a solid acid was treated with 50.00 mL of 2.000 V NaOH, which dissolved it completely (by reacting with it). There was enough excess NaOH to require 10.07 mL of 1.000 N HC1 to neutralize the excess base. What is the equivalent weight of the acid ... 

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