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pH of Solutions

pH of Solutions. Experiment # 44. From Pre Lab 30 Question # 4. 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, and the action of buffers. Universal Indicator:. neutral. 14. 1.

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pH of Solutions

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  1. pH of Solutions Experiment # 44

  2. From Pre Lab 30 Question # 4

  3. 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, and the action of buffers

  4. Universal Indicator: neutral 14 1 base acid green Pink Blue/Purple 7 An acidic solution results when the number of H+ ions exceeds the number OH- ions. When the number of H+ ions = OH- ions the solution is neutral.

  5. Acids - proton donor Bases – proton acceptor Acid- conjugate base pairs acid base acid base Bronsted-Lowery acid base definitions

  6. pH = - log [H+] 0.01 Molarity HCl =0.01 moles of H+ ions / liter of solution For all water solutions pH + pOH = 14 A solution has a pH of 2 what is the pOH? 14-2 = 12

  7. Concentration Vs. pH

  8. One number change in pH is a tenfold change in [H+] pH 3 has a [H+] 1.0X 10 -3 M And pH 4 has a [H+] 1.0X 10 -4 M

  9. K W= 1.0X10-14 What is the [OH-]; given [H +] =1.0X10-3? We can determine the [OH–] using:

  10. 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

  11. 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.

  12. Today in Lab: Part 1: Demo on pH of solutions Part 2: Demo on How to use pH meters Part 3: Follow procedure in Lab Book pg 194 Buffers and pH Part 4: Follow procedures pg 195 Hydrolysis

  13. Post Lab • Complete all Parts • Answer all questions • Complete Graph for question 3 Part A • Complete RX for table 44-1 on back of page 199

  14. H 3 O + OH- H2O + H 2 O HCl + H2O H3O+ + Cl - NH4+ + OH- H20 + NH3 NH4 OH NH4+ + OH- H20 + NaOH Na+ + OH- Na+(HCO3)- + H2O H2CO3 + OH- Na2CO3 + H2O HCO3- + OH- HC9H7O4 + H2O H3O+ + C9H7O4- NaCl + H2O Na + +Cl- +H2O

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