Strong acids acid-base reactions

Using Environmental Examples to Teach About Acids. Acid-base reactions are usually presented to secondary students as examples of aqueous equilibrium (2). In their study of acids and bases, students are expected to master the characteristic properties and reactions. They are taught to test the acidity of solutions, identify familiar acids and label them as strong or weak. The ionic dissociation of water, the pH scale and some common reactions of acids are also included in high school chemistry. All of these topics may be illustrated with examples related to acid deposition (5). A lesson plan is presented in Table I. 

Incidents of several different types have arisen from reactions involving neutralisation of an acid with a base where the exotherm (57.3 kJ/equivalent for strong acid-strong base reactions) has not occurred smoothly over an extended period, but has been sudden in effect for various reasons. Individually indexed neutralisation incidents are ... 

At the equivalence point. pH = 7.00, but only in a strong acid-strong base reaction. 

The value of Kn (1.0 X 1014) for a strong acid-strong base reaction is a large number, which means that the neutralization reaction proceeds essentially 100% to completion. After neutralization of equal molar amounts of acid and base, the solution contains a salt derived from a strong base and a strong acid. Because neither the cation nor the anion of the salt has acidic or basic properties, the pH is 7 (Section 15.14). 

As long as one of the reactants is strong, the acid-base reaction goes to completion. As you learned in Chapter 6, a reaction goes to completion when the limiting reactant is completely consumed. 

It is easy to write and balance equations for strong acid-strong base reactions. In the previous example, HCl is the acid NaOH is the base. The products are NaCl, which is a salt, and water. Now take a closer look at these reactants and their products. 

Note that the ionic equation gives more information about how a strong acid-strong base reaction occurs. When you examine the two sides of the ionic equation on page 517, you see that Na and Cl are present both as reactants and as products. Although they are important components of an overall equation, they do not directly participate in the chemical reaction. They are called spectator ions because they are present in the solution but do not participate in the reaction, Figure 15.3. 

For all these examples of strong acid-weak base reactions, the net ionic equation differs from that for a strong acid and a strong base. The sub-microscopic interactions in these strong acid-weak base reactions are between hydrogen ions and the bases. 

Figure 4.8 An aqueous strong acid-strong base reaction on the atomic scale. When solutions of a strong acid (HX) and a strong base (MOH) are mixed, the HaO from the acid transfers a proton to the OH from the base to form an H2O molecule. Evaporation of the water leaves the spectator ions, X and M, as a solid ionic compound called a salt...

Complete and balance each of the following molecular equations for strong acid/strong base reactions circle the formula of the salt produced in each. 

A precipitation reaction B oxidation-reduction reaction C combustion reaction D strong acid-strong base reaction... 

What salt would form when each of the following strong acid/strong base reactions takes place ... 

Regime D Instantaneous Reaction extremely low, it implies an instantaneous reaction. An example of this type of reaction is a strong-acid-strong-base reaction represented by the equation... 

Understand the nature of the hydrated proton, the Arrhenius definition of an acid and a base, and why all strong acid-strong base reactions have the same A// xn describe how acid strength is expressed by K, classify strong and weak adds and bases from their formulas ( 18.1) (SP 18.1) (EPs 18.1-18.12)... 

Step 3 Take a proton away. Proton transfer between the carboiyl group and the alkoxide ion gives the carboxylate anion. This strongly exothermic acid-base reaction drives the whole reaction to completion. 

Figure 4.8 An aqueous strong acid-strong base reaction as a proton-transfer process.

N,N,N, N -tetramethyl-l,8,-naph-thalenediamiDe M.P. 51 C. A remarkably strong mono-acidic base (pKg 12-3) which is almost completely non-nucleophilic and valuable for promoting organic elimination reactions (e.g. of alkyl halides to alkenes) without substitution. 

This is an acid-base reaction, in which the base is the oxide ion (p. 89) the acidic oxide SiOj displaces the weaker acidic oxide CO2 in the fused mixture. But in aqueous solution, where the 0 ion cannot function as a strong basefp. 89),carbon dioxide displaces silica, which, therefore, precipitates when the gas is passed through the aqueous silicate solution. In a fused mixture of silica and a nitrate or phosphate, the silica again displaces the weaker acidic oxides N2O5 and P4OJ0 ... 

The blocking and deblocking of carboxyl groups occurs by reactions similar to those described for hydroxyl and amino groups. The most important protected derivatives are /-butyl, benzyl, and methyl esters. These may be cleaved in this order by trifluoroacetic acid, hydrogenolysis, and strong acid or base (J.F.W. McOmie, 1973). 2,2,2-Trihaloethyl esters are cleaved electro-lytically (M.F. Semmelhack, 1972) or by zinc in acetic acid like the Tbeoc- and Tceoc-protected hydroxyl and amino groups. 

Amides are the least reactive caiboxyhc acid deiivative and the only nucleophilic acyl substitution reaction they undeigo is hydrolysis Amides are fanly stable m water but the amide bond is cleaved on heating m the presence of strong acids 01 bases Nomi nally this cleavage produces an amine and a caiboxyhc acid... 

In an acid-base reaction, the reaction unit is the proton. For an acid, the number of reaction units is given by the number of protons that can be donated to the base and for a base, the number of reaction units is the number of protons that the base can accept from the acid. In the reaction between H3PO4 and NaOH, for example, the weak acid H3PO4 can donate all three of its protons to NaOH, whereas the strong base NaOH can accept one proton. Thus, we write... 

Commercial alkylphenol ethoxylates are almost always produced by base-cataly2ed ethoxylation of alkylphenols. Because phenols are more strongly acidic than alcohols, reaction with ethylene oxide to form the monoadduct is faster. The product, therefore, does not contain unreacted phenol. Thus, the distribution of individual ethoxylates in the commercial mixture is narrower, and alkylphenol ethoxylates are more soluble in water. 

This type of cement has been further improved by the substitution of -hexyl van ill ate [84375-71-3] and similar esters of vanillic acid [121 -34-6] and/or syringic acid [530-57 ] for eugenol (93—95). These substituted cements are strong, resistant to dissolution, and, unlike ZOE and EBA cements, do not inhibit the polymerization of resin-base materials. Noneugenol cements based on the acid—base reaction of zinc and similar oxides with carboxyhc acids have been investigated, and several promising types have been developed based on dimer and trimer acids (82). 

Chemical Reactivity -/Jcflctivify with Water No reaction Reactivity with Common Materials No data Stability During Transport Stable Neutralizing Agents for Acids and Caustics Not pertinent Polymerization May occur when the product is in contact with strong acids and bases Inhibitor of Polymerization No data. 

Step 3 is new to us. It is an acid-base reaction in which the carbocation acts as a Br0n-sted acid, transferiing a proton to a Brpnsted base (water). This is the property of carbocations that is of the most significance to elimination reactions. Car bocations ar e strong acids they are the conjugate acids of alkenes and readily lose a proton to form alkenes. Even weak bases such as water are sufficiently basic to abstract a proton from a carbocation. 

Acid-base reactions in anhydrous HF are well documented. Within the Brpnsted formalism, few if any acids would be expected to be sufficiently strong proton donors to be able to protonate the very strong proton-donor HF (p. 51), and this is borne out by observation. Conversely, HF can protonate many Brpnsted bases, notably water. 

You need to know the strong acids and bases to work with acid-base reactions. 

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