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Topic #28: Titrations

Learn why titrations are crucial in understanding the concentration of unknown acids and bases through neutralization reactions. Discover the significance of indicators, equivalence points, and various methods for solving titration problems.

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Topic #28: Titrations

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  1. Topic #28: Titrations EQ: Why are titrations an important aspect of acids and bases?

  2. Acid Base Neutralization Reaction • Acid + Base  Water + Salt • Ex: HCl+ NaOH  H2O + NaCl

  3. Example: Stomach antacids

  4. Titration: • A laboratory method for determining the concentration of an unknown acid or base using a neutralization reaction. • A standard solution,(a solution of known concentration), is used. AKA the titrant. • Analyte – the solution of unknown concentration. The one being analyzed.

  5. Equivalence Point • The point at which there are stoichiometrically equivalent amounts of acid and base. • [H+] = [OH-]

  6. Buret Valve

  7. Titration Acid with Phenolpthalein End-Point

  8. Indicators • Indicators are chosen, such that they change colors at the range of the pH of interest. • The solution itself at the end-point may be: • Basic, if the reaction involves a strong base and a weak acid. • Neutral, if the reaction involves a strong acid and a strong base. • Acidic, if the reaction involves a strong acid and a weak base.

  9. Methods of Solving Titration Problems: a) using stoichiometry b) using the titration formula Maxva= b x Mbxvb M= molarity v= volume ( must be in Liters) b = number of [OH-] per base formula

  10. Ex. 1 What is the concentration of HCl if 30.0 mL of 0.10 M NaOH neutralizes 50.0mL HCl? NaOH + HCl H2O + NaCl Hint: Use Ma xva= b x Mb xvb Ma= How many moles of HCl were used? Hint: #moles= Ma x va, but convert the volume to L( 50mL=0.05L).

  11. Ex. 2 A 20.0 mL solution of Sr(OH)2 is neutralized after 25.0 mL of standard 0.05 M HCl is added. What is the concentration of Sr(OH)2? 2 HCl + Sr(OH)2 2 H2O + SrCl2

  12. Ex. 3 • How many mL of 0.20 M H3PO4 are needed to neutralize 55.0 mL of a 0.10 M solution of NaOH?

  13. Ex. 4 • What volume of 0.20M Ca(OH)2 will neutralize 45.0 mL of a 1M solution of HClO3?

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