Position du problème : les acides et les bases
Problème : pourquoi le citron est-il amer !!??
L’étude quantitative d’une réaction chimique exige le choix d’une méthode de suivi, qui permet de mesurer au moins la quantité de matière d’un des constituants du système chimique. Il y a deux familles de méthodes, les méthodes physiques qualifiés de non destructive et qui utilisent de petites quantités de matières, des méthodes chimiques qualifiés de destructive car elles utilisent de bon quantités de matières, de même elles demandent pas mal de temps vis à vis des premières . Le suivi pH-metrique fait partie de ces méthodes chimiques. Pour le suivi d’un dosage acido-basique il y a deux techniques, dosage colorimetrque relativement rapide mais moins précis, il y le dosage par suivi pH-metrique relativement lent mais plus précis, l’utilisation de matériels informatiques dans le cadre de l’EXAO à permet de rendre cette deuxième méthode beaucoup plus convivial.
Pour avoir une idée sur cette méthode, suivi le lien ci-dessous
https://physique-chimie.discip.ac-caen.fr/spip.php?article916
Cours et exercices les acides et les bases terminale science
Un acide est un corps capable de céder un ou des protons (une particule fondamentale chargée d’électricité positive) et une base est un corps capable de capter un ou des protons. … Par exemple, l’acide chlorhydrique concentré (acide fort) a un pH proche de 0 ; la soude, base très forte, a un pH proche de 14.
Exercice dosage acido-basique d’un acide qui réagi partiellement avec l’eau par une base qui réagi complètement avec l’eau. Utilisation de la méthode des tangentes pour la détermination du point d’équivalence.
Acid-Base Equilibria
6.1: Review: Defining Acids and Bases In chemistry, acids and bases have been defined differently by three sets of theories: One is the Arrhenius definition defined above, which revolves around the idea that acids are substances that ionize (break off) in an aqueous solution to produce hydrogen (H+) ions while bases produce hydroxide (OH-) ions in solution. The other two definitions are discussed in detail alter in the chapter and include the Brønsted-Lowry definition and the Lewis theory.- 6.2: Brønsted–Lowry Acids and Bases A compound that can donate a proton (a hydrogen ion) to another compound is called a Brønsted-Lowry acid. The compound that accepts the proton is called a Brønsted-Lowry base. The species remaining after a Brønsted-Lowry acid has lost a proton is the conjugate base of the acid. The species formed when a Brønsted-Lowry base gains a proton is the conjugate acid of the base. Thus, an acid-base reaction occurs when a proton is transferred from an acid to a base.
- 6.3: The pH Scale The concentration of hydronium ion in a solution of an acid in water is greater than 1.0×10−7M1.0×10−7M at 25 °C. The concentration of hydroxide ion in a solution of a base in water is greater than 1.0×10−7M1.0×10−7M at 25 °C. The concentration of H3O+ in a solution can be expressed as the pH of the solution; pH=−logH3O+pH=−logH3O+. The concentration of OH− can be expressed as the pOH of the solution: pOH=−log[OH−]pOH=−log[OH−]. In pure water, pH = 7 and pOH = 7.
- 6.4: Acid-Base Strength The strengths of Brønsted-Lowry acids and bases in aqueous solutions can be determined by their acid or base ionization constants. Stronger acids form weaker conjugate bases, and weaker acids form stronger conjugate bases. Thus strong acids are completely ionized in aqueous solution because their conjugate bases are weaker bases than water. Weak acids are only partially ionized because their conjugate bases are strong enough to compete successfully with water for possession of protons.
- 6.5: Solving Acid-Base ProblemsThe strengths of Brønsted-Lowry acids and bases in aqueous solutions can be determined by their acid or base ionization constants. Stronger acids form weaker conjugate bases, and weaker acids form stronger conjugate bases. Thus strong acids are completely ionized in aqueous solution because their conjugate bases are weaker bases than water. Weak acids are only partially ionized because their conjugate bases are strong enough to compete successfully with water for possession of protons.
- 6.6: Acidic and Basic Salt Solutions The characteristic properties of aqueous solutions of Brønsted-Lowry acids are due to the presence of hydronium ions; those of aqueous solutions of Brønsted-Lowry bases are due to the presence of hydroxide ions. The neutralization that occurs when aqueous solutions of acids and bases are combined results from the reaction of the hydronium and hydroxide ions to form water. Some salts formed in neutralization reactions may make the product solutions slightly acidic or slightly basic.
- 6.7: Lewis Acids and Bases The Brønsted-Lowry proton donor-acceptor concept has been one of the most successful theories of Chemistry. But as with any such theory, it is fair to ask if this is not just a special case of a more general theory that could encompass an even broader range of chemical science. In 1916, G.N. Lewis of the University of California proposed that the electron pair is the dominant actor in acid-base chemistry.
Physique chimie facile 
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