Unit 9 – Acids and Bases

Unit 9 – Acids and Bases Characteristics of acids:

Acids and Bases Characteristics of bases: Base nomenclature is the same as normal compounds. Ba(OH)2 is _______________.

Acid Nomenclature binary acid – hydrogen and one other element • prefix “hydro-” • other element besides hydrogen • change end to “-ic” HCl HBr H2S

Acid Nomenclature oxyacid – acid that contains oxygen If polyatomic ion suffix is “-ate”, replace it with “-ic” and add “acid” to the end. ex. HNO3 If polyatomic ion suffix is “-ite”, replace it with “-ous” and add “acid” to the end. ex. HNO2

Acid Nomenclature HC2H3O2 HI HNO3 H2SO3 HCl

Acid Nomenclature hydrofluoric acid hypochlorous acid boric acid perbromic acid hydrobromic acid

Donating and Accepting Protons In the following reaction, HCl donates its proton (H+) so it is an acid. HCl + H2O  NH3 accepts a proton so it is a base. NH3 + H2O 

Producing Ions in Solution When HCl dissolves, it produces H3O+ which is called hydronium. All acids do this in solution. HCl(g) + H2O(l)  H2SO4(l) + H2O(l)  Acidic solutions have more H3O+ than OH-.

Producing Ions in Solution NaOH dissolved in water produces OH- which is called hydroxide. All bases do this in solution. NaOH(s)  NH3(g) + H2O(l)  Basic solutions have more OH- than H3O+.

Monoprotic and Polyprotic Acids monoprotic acid – donates _________ hydrogen ion per molecule ex. HCl, HF, HC2H3O2, HNO3 diprotic acid – donates _____________ hydrogen ions per molecule ex. H2SO4, H2CO3 triprotic acid – donates ____________ hydrogen ions per molecule ex. H3PO4, H3BO3

Monoprotic and Polyprotic Acids Monoprotic acids are one and done. HCl + H2O  Diprotic acids have two reactions. H2SO4 + H2O For our purposes, assume that diprotic acids donate only one proton.

Monoprotic and Polyprotic Acids Triprotic acids go three and out. H3PO4 + H2O  Assume triprotic acids, like diprotic, donate only one proton. Once again, just because an acid has three hydrogens to donate does NOT mean that it is a strong acid. In fact, H3PO4 is weak.

Amphoteric Some compounds can act as an acid or a base depending on the reaction. This is called amphoteric. HCl + H2O  NH3 + H2O  Water is the most common amphoteric compound.

Neutralization definition – reaction between an acid and a base to form a salt and water acid + base  salt + water HCl + NaOH  HC2H3O2 + Ca(OH)2  The acid and base are both gone so the solution is _______________________. salt – any ionic compound (metal-nonmetal)

Acid-Base Neutralization Write the balanced neutralization reactions. • HNO3 and CsOH • carbonic acid and lithium hydroxide

Concentration Concentration of a compound or ion can be denoted by brackets. [H3O+] means [OH-] means A solution with [H3O+] > [OH-] is A solution with [OH-] > [H3O+] is A solution with[H3O+] = [OH-] is

Concentration • A solution has [H3O+] = 0.004 M and [OH-] = 0.00000000006 M. Is this solution acidic, basic, or neutral? • Which of [H3O+] or [OH-] is greater for a solution of sodium hydroxide?

pH scale pH – the measure of [H3O+] in a solution The pH range is usually from 0 to 14. pH 7 is acidic: [H3O+] [OH-] pH 7 is neutral: [H3O+] [OH-] (_____________ has pH = 7) pH 7 is basic: [OH-] [H3O+]

pH scale You have to be very clear on this. The lower the pH, the higher [H3O+], the more acidic the solution. The higher the pH, the lower [H3O+], the less acidic the solution.

pH scale • Solution A has a pH of 5 while Solution B has a pH of 10. Which is more acidic? Which is more basic? • Solution C has a pH of 9.5 while Solution D has a pH of 8. Which has higher [H3O+]? • Solution E has a pH of 3 while Solution F has a pH of 11. Which has higher [OH-]?

pH scale and common examples

Indicators It is easy to tell acids from bases using common indicators. Litmus paper • turns ___________ in an acidic solution • turns ___________ in a basic solution • think Phenolphthalein turns _____________ in a basic solution

Calculating pH pH = -log[H3O+] What is the pH of a solution with a [H3O+] = 0.006 M? What is the pH of a solution with [H3O+] = 0.000043 M?

Calculating pH pH = -log[H3O+] Calculate the pH of a solution with [H3O+] = 3.56 x 10-12 M. Calculate the pH of a solution with [H3O+] = 7.4 x 10-6 M.

Titration Titration is a method to determine an unknown concentration of a solution. It uses an indicator and a buret filled with the standard solution – solution of known concentration. A known volume of the unknown solution is in an e-flask and indicator is added to the flask. The standard solution is in the buret and is titrated into the e-flask until the indicator changes color.

Titration The point at which the indicator changes color is called the end point. This is the point at which [H3O+] equals [OH-].

Titration Calculations Use the equation M1V1 = M2V2 to calculate the molarity (concentration) of the unknown solution. • M1 is the molarity of the titrant in the buret. • V1 is the volume used of titrant in the buret. • M2 is the molarity of the solution in the e-flask (this is what you are looking for). • V2 is the volume of the solution in the e-flask. Titration is very useful but the measurements must be very precise. It is often useful to repeat the titration several times and use the average volume of solution titrated in the calculations.

Titration Calculations • A 0.16 M KOH solution is in a buret and it takes 43.3 mL of that solution to perform a titration. If there was 150 mL of an HCl solution of unknown concentration in the e-flask, what is the molarity of the HCl solution?

Titration Calculations • 30 mL of a CsOH solution is in an e-flask. It takes 26.4 mL of 0.250 M HBr solution in a titration to neutralize it. What is the concentration of the CsOH solution in the e-flask?

Titration Calculations • A titration requires 25.3 mL of a 1.0 M NaOH solution in a buret. The e-flask contains 75.0 mL of a HC2H3O2 solution. Calculate the concentration of the HC2H3O2 solution.

Unit 9 – Acids and Bases