Chemistry Jacqueline P. Hancock, B.S., M.Ed Acids, Bases, & Salts Chemistry Jacqueline P. Hancock, B.S., M.Ed

What is expected of me today? Lecture Practice Problems Progress Reports

Acid-Base Theories Type Acid Base Arrhenius H+ producer OH- producer BrØnsted-Lowry H+ donor H+ acceptor Lewis Electron-pair acceptor Electron-pair donor

Properties of Acids & Bases Sour taste Turn blue litmus RED React with metals to produce hydrogen gas React with carbonates to produce carbon dioxide Bases Bitter taste Turn red litmus Blue Slippery to touch Do not react with metals or carbonates

Self- Ionization of Water (Dissociation) H2O Highly polar Constant motion Pure water contains small concentration of H+ & OH- as well as H2O molec High energy collisions allows transfer of H+ ions from one H2O to another Self-ionization-reaction of like molecules to produce ions

@ 25oC Equilibrium [H+] is 1x10-7 M Equilibrium [OH-] is 1x10-7 M Therefore the ion concentrations in pure water are equal making it Neutral

Ion-Product Constant

Acid or Base? To determine whether a solution is acidic or alkaline(basic) Use the exponent value for the ion given If the H+ is greater than -7 it is.. If the H+ is less than -7 it is… If the H+ is equal to -7 it is…

Practice Problems Classify as acidic, basic, or neutral [H+]= 6x10-12 M [OH-] = 3.0x10-2 M [H+] = 2.0x10-7 M [OH-]= 1.0x10-7 M

Ion Concentration To determine the ion concentration use the Ion-product constant for water Rearrange the formula to isolate the unknown variable (solve for the missing variable) Plug in the known values Ion-Product Constant Formula g

Practice Problems If the [H+] in a solution is 1.0x10-5M, what is the [OH-] of this solution? If the hydroxide-ion concentration of an aqueous solution is 1x10-3M, what is the [H+] in the solution? Is the solution acidic, basic, or neutral?

pH 1909 Danish scientist SØren SØrensen developed pH scale of 0-14 (acid to base) pH is the negative logarithm of the hydrogen-ion concentration of a solution pH= -log[H+] pOH= -log[OH-] pH + pOH = 14

Acid pH < 7.0 [H+] > 1x10-7M Neutral pH= 7.0 [H+] = 1x10-7M Basic pH>7.0 [H+] < 1x10-7M

pH

Calculating pH Calculation pH from [H+] pH= -log[H+] 2nd -log[H+] Find the pH of each solution [H+] =1x10-4M [H+] = 0.0015M What are the pH values of the following solutions, based on their hydrogen-ion concentrations? [H+] = 1x10-12M [H+]= 0.045M

Calculating pH Calculating [H+] from pH First rearrange equation Use pH = -log[H+] First rearrange equation -log[H+] = pH Change signs log[H+] = -pH Find anti-log of value 2nd log(-pH value) Make sure in Sci mode Calculating pH from [OH-] Use Kw formula Use pH= -log[H+] First find [H+] Second find –log[H+] -log(H+ value) Answer should be positive!!!

Practice Problems Calculate [H+] for each solution pH= 5.0 pH= 12.83 Calculate the pH of the solution [OH-]= 4.3x10-5M [OH-]= 4.5x10-11M [H+] = 5.0x10-5M [H+]= 8.3x10-10M

Acid-Base Indicators Know Figure 19.2 An indicator(Hln) undergoes dissociation in a known pH range Changes colors in different solutions Limits of liquid indicators Optimal temp 250C Color sol. Can distort Dissolved salts can affect dissociation Paper indicators pH meters Know Figure 19.2 Thymol Blue Bromphenol Blue Bromcresol green Methyl Red Alizarin Bromthymol Blue Phenol Red Phenolphtalein Alizarin yellow R