Acids monoprotic

Kinetic schemes other than that embodied in Eq. (6-77) can give rise to a bellshaped curve. As in Eq. (6-77), however most of these involve two ionizations. Thus Scheme V, where HS is a monoprotic acid and B is a base (or the kinetic equivalent of S + BH ) yields a bell-shaped curve. 

From the point of view of quantitative analysis, sufficiently accurate values for the ionisation constants of weak monoprotic acids may be obtained by using the classical Ostwald Dilution Law expression the resulting constant is sometimes called the concentration dissociation constant . 

Buffer mixtures are not confined to mixtures of monoprotic acids or monoacid bases and their salts. We may employ a mixture of salts of a polyprotic acid, e.g. NaH2P04 and Na2HP04. The salt NaH2P04 is completely dissociated ... 

It functions as a monoprotic acid (pKa = 4.7) up to a pH of about 12 the acid proton is that of the thiol group in (C). Primary metal dithizonates are formed according to the reaction ... 

For the primary stage (phosphoric) V) acid as a monoprotic acid), methyl orange, bromocresol green, or Congo red may be used as indicators. The secondary stage of phosphoric) V) acid is very weak (see acid Ka = 1 x 10 7 in Fig. 10.4) and the only suitable simple indicator is thymolphthalein (see Section 10.14) with phenolphthalein the error may be several per cent. A mixed indicator composed of phenolphthalein (3 parts) and 1-naphtholphthalein (1 part) is very satisfactory for the determination of the end point of phosphoric(V) acid as a diprotic acid (see Section 10.9). The experimental neutralisation curve of 50 mL of 0.1M phosphoric(V) acid with 0.1M potassium hydroxide, determined by potentiometric titration, is shown in Fig. 10.6. 

Boric acid behaves as a weak monoprotic acid with a dissociation constant of 6.4 x 10-10. The pH at the equivalence point in the titration of 0.2M sodium tetraborate with 0.2 M hydrochloric acid is that due to 0.1 M boric acid, i.e. 5.6. Further addition of hydrochloric acid will cause a sharp decrease of pH and any indicator covering the pH range 3.7-5.1 (and slightly beyond this) may be used suitable indicators are bromocresol green, methyl orange, bromophenol blue, and methyl red. 

Discussion. Boric acid acts as a weak monoprotic acid (Ka = 6.4 x 10"10) it... 

In the direct method, a solution of the ammonium salt is treated with a solution of a strong base (e.g. sodium hydroxide) and the mixture distilled. Ammonia is quantitatively expelled, and is absorbed in an excess of standard acid. The excess of acid is back-titrated in the presence of methyl red (or methyl orange, methyl orange-indigo carmine, bromophenol blue, or bromocresol green). Each millilitre of 1M monoprotic acid consumed in the reaction is equivalent to 0.017032 g NH3 ... 

Neutralisation reactions. The equivalent of an acid is that mass of it which contains 1.008 (more accurately 1.0078) g of replaceable hydrogen. The equivalent of a monoprotic acid, such as hydrochloric, hydrobromic, hydriodic, nitric, perchloric, or acetic acid, is identical with the mole. A normal solution of a monoprotic acid will therefore contain 1 mole per L of solution. The equivalent of a diprotic acid (e.g. sulphuric or oxalic acid), or of a triprotic acid (e.g. phosphoric( V) acid) is likewise one-half or one-third respectively, of the mole. 

The principal difference between a polyprotic acid and a monoprotic acid is that a polyprotic acid donates protons in a succession of deprotonation steps. For example, a carbonic acid molecule can lose one proton to form I ICO , and then that ion can donate the remaining proton to form CO, 2. We shall see how to take this succession of deprotonations into account when assessing the pH of the solution of a polyprotic acid or one of its salts. In addition, we shall see how the relative concentrations of the ions in solution, such as P043, HP042, and H,P04 depend on the pH of the solution. 

Calculate the pH of each of the following acid solutions at 25°C ignore second deprotonations only when that approximation is justified, (a) 1.0 X 10 4 M H BO (aq), boric acid acts as a monoprotic acid (b) 0.015 m H,P04(aq) ... 

Because many biological systems use polyprotic acids and their anions to control pH, we need to be familiar with pH curves for polyprotic titrations and to be able to calculate the pH during such a titration. The titration of a polyprotic acid proceeds in the same way as that of a monoprotic acid, but there are as many stoichiometric points in the titration as there are acidic hydrogen atoms. We therefore have to keep track of the major species in solution at each stage, as described in Sections 10.16 and 10.17 and summarized in Figs. 10.20 and 10.21. 

Below is the titration curve for the neutralization of 25 mL of a monoprotic acid with a strong base. Answer the following questions about the reaction and explain your reasoning in each case, (a) Is the acid strong or weak (b) What is the initial hydronium ion concentration of the acid (c) What is K, for the acid (d) What is the initial concentration of the... 

Mond process The purification of nickel by the formation and decomposition of nickel carbonyl, monomer A small molecule from which a polymer is formed. Examples CH2=CH2 for polyethylene NH2(CH2)6NH2 for nylon, monoprotic acid A Bronsted acid with one acidic hydrogen atom. Example CH COOI I. monosaccharide An individual unit from which carbohydrates are considered to be composed. Example C6H(206, glucose, multiple bond A double or triple bond between two atoms. 

We will calculate the pH shift that results when 0.1 Monoprotic Acids... 

Consider the case of the monoprotic acid, HA, which forms the sodium salt (in 0.15 M NaCl) when the solubility product, IQp, is exceeded. In additions to Eqs. (2a) and (10a) above, one needs to add the following equation to treat the case. 

An additional (electrostatic) shift occurs if the lipid vesicles or micelles have a charged surface, according to the expression suitable for monoprotic acids and bases... 

The membrane permeabilities Pm may be converted to intrinsic permeabilities P(h when the pKa is taken into consideration. An ionizable molecule exhibits its intrinsic permeability when it is in its uncharged form and there is no water layer resistance. The relationship between Pm and P0 is like that between the pH-dependent apparent partition coefficient (log Kd) and the true partition coefficient (log Kp), respectively. This relationship can be rationalized by the mass balance. Take, for example, the case of a monoprotic acid, HA. The total substance concentration is... 

The widely used term log P refers to the logarithm of the partition coefficient P of the unionized species, which is P° for a base with no acidic functions, and P1 for a monoprotic acid or an ordinary ampholyte. Log P is equal to log D at any pH remote from the pKa where the molecule exists entirely in its unionized form. Log D at any pH is equal to log P for a non-ionizable molecule. 

Equations have been published [16] which relate pKa and p0Ka values to partition coefficient (P) values for monoprotic acids and bases, and diprotic acids, bases and ampholytes. For example, P1 for a monoprotic acid is calculated from... 

Method 2 The pH is determined from the concentration of the salt. Even when the volume of solution is given, it is not necessary to use that information. We can calculate the concentration of a salt derived from a monoprotic acid and a base with one OH group by ... 

For proton transfer between a monoprotic acid HA and a base B,... 

The neutralization reaction is HA + OH => A + H2 O, where HA is the weak acid and A is its conjugate base. This assumes that HA is a monoprotic acid. Because the principal product of this reaction is the weak base, A, the resulting solution will be basic with a pH greater than 7. 

The weak acid curves can also be calculated. This involves the use of the equilibrium constant expression for a weak monoprotic acid ionization ... 

The answer is in the expression for the ionization constant, K l or Kb, where the ratio of the conjugate acid and base concentrations is found. In the case of a weak monoprotic acid, HA, we have the following ... 

Define monoprotic acid, polyprotic acid, monobasic base, polybasic base, titration curve, and inflection point. 

Monoprotic acid—An acid that has just one hydrogen ion to donate per molecule. 

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