Definitions Examples and types of acids and bases Properties pH and pOH Neutralization

Acid Anything that produces hydrogen ions in a water solution. HCl (aq) H + + Cl -Base Anything that produces hydroxide ions in a water solution. NaOH (aq) Na + + OH - Arrhenius Definition Arrhenius definition is limited to aqueous solutions. There are many definitions, but the most convenient for this course is this one.

Acid A proton donor NaOH + HCl (aq) NaCl + H 2 OBase A proton acceptor HCL + NaOH (aq) NaCl + H 2 O Br Ø nsted-Lowry Definition

Examples and types of acids ACIDFORMULACOMMON NAME (Inorganic or mineral) NitricHNO 3 aqua fortis Hydrochloric HClmuriatic acid SulfuricH 2 SO 4 oil of vitriol carbonicH 2 CO 3 carbonated water (Organic) FormicHCOOH AceticHC 2 H 3 O 2 vinegar

Examples and types of bases BASEFORMULA Sodium hydroxideNaOH Potassium hydroxideKOH Ammonium hydroxideNH 4 OH Calcium hydroxideCa(OH) 2 Magnesium hydroxideMg(OH) 2 Magnesium and calcium hydroxide are used as antiacids. Magnesium hydroxide is known as Milk of Magnesia.

General properties of acids 1. Acids react with active metals to produce hydrogen gas. Zn(s) + 2HCl(aq) ZnCl 2 + H 2 Question: How can you test for hydrogen? 2. Acids affect the colors of acid-base indicators. 3. Acids and bases are electrolytes. 4. Acids neutralize bases. 5. Dilute acids have sour taste. (Citrus fruits, vinegar and sour milk taste sour because of the presence of dilute acids). Some acids are poisonous.

The pH and/or pOH is a measure of the acidity or alkalinity of an aqueous solution Increasing acidity Neutral Increasing basicity pH Increasing basicity Increasing acidity pOH

The pH-meter is a device used to find the pH of a solution.

pH indicators: Organic substance that changes color according to the pH.

Dissociation constant, K a /K b HAc H + + Ac K a = #### The pH depends on the hydrogen ions concentration [H + ] and this concentration depends on the dissociation constant K a or K b. Strong acids/bases are highly or completely dissociated. Weak acids are just partially dissociated. The higher K a the higher the [H + ].

IONIZATION OF ACIDS ACIDIonization equation Ionization constant, Ka hydrochloricHCl ---> H + + Cl - Very large nitricHNO 3 ---> H + + NO 3 - Very large sulfuricH 2 SO4 ---> H + + HSO 4 - Large acetic HC 2 H 3 O 2 H + + C 2 H 3 O x10 -5 hydrosulfuricH 2 S H + + HS - 9.5x10 -8 hydrofluoricHF H + + F-3.5x10 -4

pH calculations Pure water is neutral (pH = 7) because the hydrogen ions concentration equals the hydroxide ions concentration. [H + ] = [OH - ] = 1.0 x M From this equation we can say that [H + ]x[OH-] = 1.0 x (1) By using logarithms, we obtain the following equations: pH + pOH = 14(2)

pH = -log [H + ](3) pOH = -log [OH-](4) Given the pH/pOH how do you solve for [H + ] and/or [OH-]????? (5) and (6) Both the hydrogen ions concentration, [H + ], and the hydroxide ions concentration, [OH-], are expressed in Molarity (moles per liter of solution). For a strong acid, the molar concentration (M) is the same [H + ], for a base, the molar concentration is the same [OH-].

Thus, 0.01 M, HCl has [H + ] = 0.01 M M, NaOH has [OH - ] = M pH scale works only for concentrations below 1 M. Exercise: What is the pH of 1.3 x10 -3 M, HCl solution? Answer: pH = - log [H + ], then pH = - log [1.3x10 -3 ] pH = 2.88

A neutralization is a chemical reaction in which an acid is neutralized by a base or viceversa to produce salt and water. In this reaction the hydrogen ions from the acid react with the hydroxide ions from the base to produce water. The point at which the neutralization finishes is called the EQUIVALENCE POINT. NEUTRALIZATION