Chemistry – May 13, 2019 P3 Challenge – H2SO4 + 2 OH-  2 H2O + SO42- A) Identify acid, base, conjugate acid, conjugate base B) Draw a bracket line connecting conjugate acid- base pairs Get out Acid Base WS pg 1 for HMW check

Chemistry – May 13, 2017 Today’s Objective – pH Assignment: Agenda Acid/Base pH Worksheet Quest on Wednesday Agenda Homework Review Self-ionization of water pH, pOH Classwork on pH table Quest description Review of pH table

Water Because water is amphoteric: can act as an acid or a base. Water can react with itself, acting as both the acid and base: H2O(l) + H2O(l)  H3O+ (aq) + OH- (aq) This reaction is the self-ionization of water, and happens in very small amounts. In pure water at 25◦C, [H+] = [OH-] = 1 x 10-7 M = 0.0000001 M Product of these two concentrations is called the ion product of water Kw = 1 x 10-14 = [H+] [OH-] The ion product of water is true for all acidic or basic solutions. H3O+ = H+

Relative concentrations [H+] [OH-] Kw 1.E-01 1.E-13 1.E-14 1.E-02 1.E-12 1.E-03 1.E-11 1.E-04 1.E-10 1.E-05 1.E-09 1.E-06 1.E-08 1.E-07

pH pH = -log [H+] [H+] Opp of Exp pH 1.E-01 1 1.E-02 2 1.E-03 3 1.E-04 5 1.E-06 6 1.E-07 7 1.E-08 8 1.E-09 9 1.E-10 10 1.E-11 11 1.E-12 12 1.E-13 13 Easier to refer to [H+] based on the exponent. More specifically the opposite of the exponent because they are negative. We call this value pH. Small pH values, have highest [H+] Mathematically, pH = -log [H+]

Acidic, Basic, or Neutral pH pH is by far the most common way to describe the acidity/basicity of a solution Always remember that pH is a log function: each increase by 1 is a factor of 10. Ex: pH = 7 pH = 3.2 pH = 8.2

pOH It is much less common than pH, but you can similarly define pOH pOH = -log [OH-] Low pOH values are basic, high pOH values are acidic, 7 is neutral. pH +pOH = 14 Ex: If pOH = 4, pH = Ex: If pOH = 10, pH = Often easiest, to convert pOH to pH when identifying acidity.

pH Calculations Four related quantities: pH, pOH, [H+] and [OH-] pH = -log [H+] , pOH = -log [OH-], Kw = [H+] [OH-] = 1 x 10-14 , pOH + pH = 14 Note: the opposite of pH = -log [H+] is [H+] = 10 –pH Calculate the other three quantities for the given information. Then indicate if it is an acidic or basic solution. [H+] = 4.0 x 10-3 M [OH-] = 1.5 x 10-5 M pH = 2.1 pOH = 3.5

Quest Description 3 x 4 pts Balance and Write Keq 1 x 8 pts Calculation with Keq 7 x 2 pts Equilibrium L/R shifts 1 x 4 pts A/B/CA/CB equation 12 x 1 pt pH/pOH etc.. table

Exit Slip - Homework Exit Slip: An acidic solution has [H+] = 4.5 x 10-4 M. What are a) the pH b) the pOH and c) [OH-] What’s Due? (Pending assignments to complete.) Acid/Base pH worksheet - Show me by end of class What’s Next? (How to prepare for the next day) Read p496 - 520