Experiment 5: Acid-Base Titration

• In 1884 Svante Arrhenius proposed the first theoretical model for acids and bases.
• Arrhenius acid, is any substance that liberates H+ ions when placed in water. It causes the concentration of H+ ions to be higher than that of

  OH- ions.
• Brønsted and Lowry acid is defined as substances that donate H+ ions (protons) and therefore are called proton donors.
• Bronsted and Lowry bases are substances that accept H+ ions and are defined as proton acceptors.
• Titration is a process by which a standard solution is gradually added to a volume of a solution whose concentration is being determined.
• Acid-base neutralization occurs when equivalent quantities of an acid and a base are mixed (equivalents acid equals equivalents base).
• pH is defined as the negative logarithm of the H3O+ molar

  concentration
• In pure water, [H3O+] = 10^-7, and the pH = 7.
• A pH value lower than 7 corresponds to an acidic condition, while a pH higher than 7 is basic.
• Solutions containing substances with the ability to donate protons and substances with the ability to accept protons are called buffers.
• The amount of acid or base a buffer can accept without significant pH change is called the buffer capacity.
• A buffer consists of a solution containing about equal amounts of a weak acid and the salt (anion) of the weak acid.
• A less accurate method of measuring pH level is the use litmus papers where the red paper turns blue above pH = 8.00 and blue paper turns red below pH = 5.00.
• A base liberates OH- ions when placed in water. The resulting solution has a higher concentration of OH- ions than H+ ions and is said to be basic, or alkaline.
• A Lewis acid is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct.
• A Lewis base is any substance, such as the OH- ion, that can donate a pair of nonbonding electrons. A Lewis base is therefore an electron-pair donor. 
• All Arrhenius acids and bases are Brønsted-Lowry acids and bases as well. However, not all Brønsted-Lowry acids and bases are Arrhenius acids and bases.
• A Bronsted-Lowry acid-base reaction occurs when an acid and a base react to form their conjugate base and conjugate acid, respectively
• An acid reactant produces a base product and the two constitute an acid-base conjugate pair. A base reactant produces an acid product which is a base-acid conjugate pair
• The conjugate acid of the pair has one more H and one less negative charge than the base.
• The conjugate base of the pair has one fewer H and one more negative charge than the acid.
• A strong acid completely transfers its protons to water, leaving no

  undissociated molecules in solution. Its conjugate base has a negligible

  tendency to be protonated (to accept protons) in aqueous solution.
• A weak acid only partially dissociates in aqueous solution and therefore exists

  in the solution as a mixture of the acid and its conjugate base. The conjugate

  base of a weak acid shows a slight ability to remove protons from water.
• A substance with negligible acidity contains hydrogen but does not

  demonstrate any acidic behavior in water. Its conjugate base is a strong base, reacting completely with water, abstracting protons to form OH- ions.
• Amphiprotic susbtances are substances that can both donate and accept protons depending on the conditions. On the other hand, amphoteric substances are those that can act both as an acid and as a base. 
• The p-value is the negative logarithm (to the base 10) of the molar concentration of that species.
• [H3O+] from the auto-ionization of water is negligible (it is very, very small). Hence, pH is largely from the acidic compound. Concentration of dissociated acid, [HA]dissociation, is very small such that the total amount of [HA] at equilibrium is approximately the same as initial amount. % dissociation is lesser than 5%