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pH of Solutions

pH of Solutions. Experiment # 44. Introduction. Purpose: To find the pH of several common solutions, noting the range of the ph scale, to study the relationship between conjugate pairs of acids & bases the action of buffers. Introduction.

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pH of Solutions

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  1. pH of Solutions Experiment # 44

  2. Introduction • Purpose: • To find the pH of several common solutions, noting the range of the ph scale, • to study the relationship between conjugate pairs of acids & bases • the action of buffers

  3. Introduction • An acid solution results when the number of H+ ions exceeds the number oh OH- ions. When the number of H+ ions = OH- ions the solution is neutral. Universal Indicator neutral base acid 7 14 1 pink blue/purple green

  4. pH = - log [H+] • 0.01 Molarity HCl = 0.01 moles of H+ ions per Liter of solution [H+] x [OH-] = 1.0 x 10 -14 For all water solutions….. pH + pOH = 14 Example: [H+] = 10-9 , then [OH- ] = 10-5 pH = 9 pOH = 5

  5. pH Demo, Table 44-1 pH of Common substances Part 1, Demo Review Standardization of pH meters Part 2, Demo Part 3, Follow procedure in Lab Book Part 4, follow procedure

  6. Buffers & pH You will see how buffers resist large changes in pH. A buffer is usually a weak acid and its conjugate base. HC2H3O3 which can donate H + ions and lower pH and C2H3O3- which can accept a H+ ion. If the [OH-] of a solution is increased, the acid portion of a buffer system donates a H+ to neutralize the OH-. If the [H+] increases the conjugate base of the buffer will act to accept the H+ , so the pH will not change significantly. H+ OH- C2H3O3 - HC2H3O3

  7. Hydrolysis Objective : to see whether a salt reacts with water Hydrolysis is the cleavage ( lysis ) of water. When a + or - ion reacts with water to produce H+ or OH-, the pH changes. However not all ion react with water, if there is no reaction, the pH does not change. Part 4.

  8. Post Lab • Complete all Parts • Answer all questions • Use GA for graph of Part 3, A, pH vs Drops for water and buffer • Complete RX for table 44-1 on back of page 199

  9. HCl + H2O H3O+ + Cl - H20 + H2O H3O+ + OH - H20 + NH3 NH4+ + OH- H20 + NaOH Na+ + OH- Na+(HCO3-) + H2O H2CO3 + OH- Na2CO3 + H2O HCO3- + OH- NaCl + H2O Na + + Cl- +H2O NH4+ + OH- NH4 OH HC9H7O4 + H2O H3O+ + C9H7O4- RX

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