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Agenda 5-13-07

Agenda 5-13-07. Do Now : 1.write the products of the reaction when the reactants given below undergoes double replacement reaction and balanced the equation: AB + CD -----> CB + AD HCl (aq) + Mg(OH) 2(s) ------>

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Agenda 5-13-07

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  1. Agenda 5-13-07 • Do Now: 1.write the products of the reaction when the reactants given below undergoes double replacement reaction and balanced the equation: AB + CD -----> CB + AD HCl(aq) + Mg(OH)2(s) ------> 2. Define the ff on page 525 - 528: buffer solution, standard solution, titration and equivalence point • HW for tomorrow: Check website under HW • Objectives • Explain Neutralization Reaction in terms of acid base reaction • Solve problems involving neutralization in acid base reaction • To understand the general characteristic of buffered solution • Upcoming: Test on Friday ( types of decays, nuclear stability, half-life, acid-base reaction) Don’t Forget to study!

  2. Review

  3. What is the difference between Acid And base according to Arrhenius Theory? What’s the difference?

  4. Acid produces H+ in aqueous solution • HCl (g) ------------> H +(aq) Cl- (aq)

  5. Bases Produces OH- in aqueous Solution NaOH (s) -----> Na+(aq) + OH-(aq)

  6. What is the difference between Acid And base according to Bronsted-Lowry Theory? What’s the difference?

  7. What is an indicator?

  8. Indicator • Substances that exhibit different colors in acidic and basic solutions • It has a weak acid and a conjugate base

  9. Explain neutralization reaction Objective #1

  10. What happen when an acid reacts with a base? HCl + NaOH ---> HCl + NaOH ---> H2O + NaCl Neutralization Reaction a type of double replacement reaction  A reaction between an acid and a base to form a neutral solution

  11. Neutralization Reaction • Acid and base properties combine to form water H+ + OH- -------> H2O Note: water is one of the products of neutralization reaction

  12. Exercise • Write the products of the reaction below and balance the equation H2SO4 + NH4OH ----> H2SO4 + NH4OH ----> (NH4)2SO4 + H2O H2SO4 + 2 NH4OH ----> (NH4)2SO4 + 2 H2O

  13. Acid Base Titration • Is a useful application of neutralization reaction • A process of adding a solution of accurately known concentration, standardsolution, ( titrant) to another solution of unknown concentration,( analyte until the chemical reaction between the two is complete ( the equivalence point) or end point • Equivalence point is the point in titration where the indicator used undergoes a color change • Note; indicator changes color at pH=7

  14. How Does it Work? Load the titrant to OH- Base the burette and add the OH- titrant slowly to the analyte OH-OH- until exactly enough base OH- has been added to just react with all the analyte Acid with indicator H+ H+ H+ H+-

  15. OH- OH-OH- OH- Has reached its equivalence point H+ H+

  16. At the equivalence point, n Acid = n base, to get the molarity of the base or acid M = n = moles V L M acid = n acid , M base = n bas V acid Vbase nA = nB MAVA = MBVB

  17. Ex: • In a titration, It takes 6mL of 0.5MNaOH to neutralize 15mL of HCl. What is the concentration of HCl? NaOH + HCl -----> NaCl + H2O molar ratio ( 1:1) MA VA = MBVB MA= MBVB = (0.500M)(6mL) VA 15mL = 0.2M

  18. Sample 2 • A 25.0mL of sulfuric acid solution requires 32.58mL of .500M NaOH to neutralize it. What is the molarity of H2SO4? Solution: 1.Write the balance equation H2SO4 + NaOH ---> H2SO4 + NaOH ---> Na2SO4 + H2O H2SO4 + 2 NaOH ---> Na2SO4 + 2 H2O 2mole NaOH : 1 mole H2SO4 2.Determine the number of moles of NaOH M = n , n = MV n = (0.500moles) ( 0.03258L) = 0.01629 moles V L 3.Determine the molarity of H2SO4 using nA = nB M = n , M = 0.01629moles NaOH x 1mole H2SO4 V 0.025L 2mole NaOH M H2SO4 = 0.3258M

  19. Prob.#1 • What volume of 1.5M NaOH is needed to react with 25mL of 4M HCl? Solution: 1.Write the balanced equation: HCl + NaOH ----> NaCl + H2O Ans VB = 67mL or 0.067L

  20. Problem#2 In a titration, 50.0mL 0f 0.1204 M HCl requires 48.54mL NaOH solution for neutralization. What is the molarity of the NaOH solution?

  21. Problem #3 What Volume of 0.150M HNO3 solution is needed to neutralize 45.0mL of a 0.550M KOH solution? Given: MA = 0.150 MB = 0.550M VA = ? VB = 45mL Solution 1.

  22. Problem#4 • How many mL of 0.2056M NaOH is required to completely

  23. How important is pH in living things?

  24. pH plays an important role • Most living organisms survive in a narrow pH Ex: human blood is maintained between 7.35 to 7.45 by buffering system

  25. Buffers • resist a change in pH even when a strong acid or base is added to it • Contains --->weak acid and its conjugate base  weak base and its conjugate acid

  26. Note: • Buffers has a remarkable property of maintaining an almost constant pH even with the addition of a strong base or acid due to the presence of the weak acid that neutralizes any added base and also a weak base that neutralizes any added acid.

  27. Ex: • 1M CH3COOH and 1M NaCH3OO acetic Sodium acid acetate Added w/ a base CH3COOH + OH- ---> H2O + CH3COO- Added w/ an acid CH3COO + H3O+ --> H2O + CH3COOH Note: acetate ion will neutralize any added acid -

  28. What happens if the blood becomes basic or acidic? • The bicarbonate-carbonic acid ( HCO3/H2CO3) buffer will buffer the blood. • If it becomes basic, the carbonic acid will neutralize the OH- ions  If it becomes acidic, the bicarbonate will neutralize the H3O+.

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