The concept of strong and weak

Svante Arrhenius, like Berzelius, was born in Sweden and spent his entire professional career there. According to Arrhenius, the concept of strong and weak acids and bases came to him on May 13,... 

Inorganic and physical chemistry Chemical equilibrium 3 The concept of strong and weak... 

The results obtained imply a rather small probability of large-size clusters comprising many particles for a weakly hierarchical system the reverse is true for a strongly hierarchical system. Thus, the structural implications of the concept of strongly and weakly hierarchical systems become more transparent. 

An extension in principle applicable to every model is the concept of strong and weak binding sites according to Dzombak and Morel, 1990, and the 1-pK approach by Bolt and Van Riemsdijk, 1982. 

Liquid crystals in confined geometries are known to be influenced by the orientation of the director at the boundaries. Section 2.6 introduces various ideas on boundary conditions and the concepts of strong and weak anchoring of the director at the boundaries. Finally, Section 2.7 gives a simplifying reformulation of... 

A base is any material that produces hydroxide ions when it is dissolved in water. The words alkaline, basic, and caustic are often used synonymously. Common bases include sodium hydroxide (lye), potassium hydroxide (potash lye), and calcium hydroxide (slaked lime). The concepts of strong versus weak bases, and concentrated versus dilute bases are exactly analogous to those for acids. Strong bases such as sodium hydroxide dissociate completely while weak bases such as the amines dissociate only partially. As with acids, bases can be either inorganic or organic. Typical reactions of bases include neutralization of acids, reaction with metals, and reaction with salts ... 

In Chapter 4, we introduced the concept of acids and bases. Acids and bases may be strong or weak. Strong acids completely dissociate in water and weak acids only partially dissociate. For example, consider two acids HC1 (strong) and CH3COOH (weak). If we add each to water to form aqueous solutions, the following reactions take place ... 

Stockmayer and Hecht (1953) have developed an additional mathematical theory of the heat capacity of chain polymeric crystals. Their theory is based on the concept of strong valence forces between atoms in the polymeric chain and of weak (non-zero) coupling between chains. This model corresponds to that also proposed by Tarassov (1952). There are not many low temperature specific heat data on polymers, but the Stockmayer-Hecht theory can be tested by calculating the Tm constant... 

Section 19.1 discusses the Brpnsted theory of acids and bases, which extends the concepts of add and base beyond aqueous solutions and also explains the acidic or basic nature of solutions of most salts. Dissociation constants, the equilibrium constants for the reactions of weak acids or bases with water, are introduced in Section 19.2. The concept of the ionization of covalent compounds is extended to water itself in Section 19.3, which also covers pH, a scale of acidity and basicity. Section 19.4 describes buffer solutions, which resist change in their acidity or basicity even when some strong acid or base is added. Both the preparation and the action of buffer solutions are explained. Section 19.5 discusses the equilibria of acids containing more than one ionizable hydrogen atom per molecule. 

The concept of Wanzlick (and Ofele) to react the imidazolium salt with a basic transition metal complex can be modified - and generalised - by separating the base and the transition metal complex. In this case, an equilibrium between the imidazolium salt and its deproto-nated form, the carbene, is established. Although the equilibrium is very much on the side of the imidazolium salt, by far the weaker conjugate acid, the reaction is shifted towards the carbene by strong coordination of the NHC ligand to the transition metal. Examples for weak bases used in this context include Na COj [73], K COj [74-77], CS2CO3 [78], NEtj [79,80], pyridine [76] and NaOAc [81,82],... 

The distinction between strong and weak acids and bases is important when one intends to recover the exchanged ions (see section 4.5.4 on Elution and choice of eluent), and the same concept applies equally to... 

Notice that dynamic equilibrium includes the concepts of sameness and constancy that we discussed in Section 15.1. When dynamic equilibrium is reached, the forward reaction rate is the same as the reverse reaction rate (sameness). Because the reaction rates are the same, the concentrations of the reactants and products no longer change (constancy). However, just because the concentrations of reactants and products no longer change at equilibrium does not imply that the concentrations of reactants and products are equal to one another at equilibrium. Some reactions reach equilibrium only after most of the reactants have formed products. (Recall strong acids from Chapter 14.) Others reach equilibrium when only a small fraction of the reactants have formed products. (Recall weak acids from Chapter 14.) It depends on the reaction. 

Eq. (28). The theory uses the concept of internal and external degrees of freedom of the polymer molecule, the former related to the strong intramolecular valence forces and the latter to the weak inter-molecular Van der Waals forces. A smoothed potential of the Lennard-Jones type is taken to represent the potential energy of interaction between the. two segments of polymer. Xj 2 X 3 were found to depend on the potential energy and the lattice coordination number. 

In Chapter 4 (Section 4.6), we introduced the concept of acids and bases. We can now look at the concept of equilibrium associated with the dissociation of weak acids and weak bases in water. Remember that strong acids and strong bases dissociate in water, they completely dissociate and a forward reaction does not exist. 

The concept of degree of dissociation made it possible to distingnish strong electrolytes (where the valnes of a in the solntion are close to nnity) and weak electrolytes (where the valnes of a are low). This distinction is somewhat arbitrary, since according to Eq. (7.10) the degree of dissociation depends on solntion concentration. 

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