Equilibrium constant for a base

The equilibrium constant for a reaction in which a base accepts a proton from the solvent (i b)-... 

The experimental value of Kb for ammonia in water at 25°C is 1.8 X I(T5. This small value tells us that normally only a small proportion of the NH molecules are present as NH4+. Equilibrium calculations show that only about 1 in 100 molecules are protonated in a typical solution (Fig. 10.16). In general, the basicity constant for a base B in water is... 

In these equations, HA symbolizes a weak acid and A symbolizes the anion of the weak acid. The calculations are beyond our scope. However, we can correlate the value of the equilibrium constant for a weak acid ionization, Ka, with the position of the titration curve. The weaker the acid, the smaller the IQ and the higher the level of the initial steady increase. Figure 5.2 shows a family of curves representing several acids at a concentration of 0.10 M titrated with a strong base. The curves for HC1 and acetic acid (represented as HAc) are shown, as well as two curves for two acids even weaker than acetic acid. (The IQ s are indicated.)... 

Earlier, we noted that the conjugate base of a weak acid is a weak base, and the conjugate acid of a weak base is a weak acid. We also derived an exceedingly important relation between the equilibrium constants for a conjugate acid-base pair Ks- Kb = Kk. 

Problems in this chapter include some brainbusters designed to bring together your knowledge of electrochemistry, chemical equilibrium, solubility, complex formation, and acid-base chemistry. They require you to find the equilibrium constant for a reaction that occurs in only one half-cell. The reaction of interest is not the net cell reaction and is not a redox reaction. Here is a good approach ... 

When more than one conjugate add-base pair is in equilibrium with water, the exact mathematical relations for calculation of [H" "] become complex, especially if a single equation is to represent all possible initial conditions. The derivation of such equations can clarify the nature of approximations made in practical applications. In many cases, however, simplification may be achieved at the outset by using approximate calculations to estimate the concentrations of the major species concerned and then testing the validity of the approximations. If the concentration levels or equilibrium constants for a system are so unusual that the simple equations are not valid, exact equations can be used. " ... 

The equilibrium constant for (31) at 100 C decreases by a fraction of ca. 10 on transfer from DMAC to 88 % MeOH-HgO. This is because the Sif2 anion-cation reaction is much more strongly influenced by solvent transfer than the back reaction between polar molecules. The large change in equilibrium constant for a process of this charge type with solvent transfer warns us that acid-base indicator systems of this charge... 

The equilibrium constant for a proton transfer reaction from a series of proton donors (SH) to base (B) (Equation 18) has a peq value of unity for the Bronsted dependence on the pX of SH (pX, ). 

Determinations of the ERE of quinoline from thermochemical data have given results which range from 47.3 to 69 kcal mole-1.49-271-272 There appear to be no corresponding estimates for isoquinoline, but a value of 48 9 kcal mole-1 has recently been deduced from a comparison of the equilibrium constants for pseudo-base formation of iV-methylisoquinoline cation and its dihydro analog 73.273 Comparison of these ERE values with those obtained for naphthalene (61-75 kcal mole-1) shows that they parallel the somewhat lower resonance energy of pyridine relative to that of benzene. 

Stability Constants There are certain cases in which the equilibrium constant for a reaction of the sample with some substance can be easily measured and yields valuable structural information. Useful structural information is forthcoming only when there have been previous studies of related equilibria, as is the case with acids and bases. 

An acid dissociation constant, Aa, (also known as acidity constant, or acid-ionization constant) is a quantitative measure of the strength of an acid in solution. It is the equilibrium constant for a chemical reaction known as dissociation in the context of acid-base reactions. The equilibrium can be written symbolically as ... 

The equilibrium constants for copper-based ATRP were determined for a wide range of nitrogen-based ligands and initiators in MeCN at 22 °C. Values of Katrp were measured with CuBr/L complexes and EBriB (constant Kbh and Kea). The results displayed a linear correlation between Katrp and 1/2 (i.e., ffEx) for the series of Cu complexes formed with the different ligands. Figure g xhe correlation should be... 

This equilibrium constant is based on activity, not concentration. It now must be converted to a concentration-based equilibrium constant. For a gas,... 

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