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Titration

Titration. Neutralization & Acid-Base Titrations. Neutralization Reaction. A neutralization reaction is special type of double displacement reaction between an acid and a base In a reaction, acids and bases are both aqueous, so the ions are available to recombine:

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Titration

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  1. Titration Neutralization & Acid-Base Titrations

  2. Neutralization Reaction • A neutralization reaction is special type of double displacement reaction between an acid and a base • In a reaction, acids and bases are both aqueous, so the ions are available to recombine: HCl(aq) + KOH(aq) HOH(l) + KClaq) acid base water salt (neutral ionic compound) • The acid donates H+ and the base accepts, forming HOH(l) (water, H2O)

  3. Because acids & bases are aqueous solutions, stoichiometry calculations can be used with acids and bases: C1V1 = C2V2 Because acids & bases often combine in ratios other than 1:1, we need a slight modifation CaVaA = CbVbB Where A & B represent the Acid/Base coefficient Ex: 55.3 mL of 0.1 M NaOH is used to neutralize 450mL of HCl. What is the HCl concentration? Acid-Base Stoichiometry

  4. Acid-Base Stoich: Step 1 – Balanced Chem Eq’n HCl + NaOH  NaCl + HOH Step 2 – in this case, A = 1 & B = 1, so they can be ignored CaVbA = CaVbB Ca(0.450L)(1)= 0.1M(0.0553L)(1) Ca = 0.01225 M

  5. Step 1 – Balanced Chem Eq’n 2HCl + Ca(OH)2 CaCl2 + 2 HOH Step 2 – in this case, A = 1 & B = 2 CaVbA = CaVbB Ca(0.450L)(1)= 0.1M(0.0553L)(2) Ca = 0.025 M (twice as much as the first question, because acid:base ratio is now 2:1) Acid-Base Stoich:

  6. Titrations • The above calculations are used in titration experiments • Titrations are commonly used in chemistry labs to determine the unknown concentration of an acid or base solution

  7. Titrations (Cont’d) 8 A solution of known concentration (titrant) is slowly added to the unknown solution until neutralization is reached End Point: an indicator, added to the unknown, will change colour when the pH has changed Equivalence Point: the point at which moles of base = moles of acid

  8. The titrant in the buret is slowly added to the unknown in the flask A colour change occurs (end point) telling us neutralization has happened (equivalence point) http://group.chem.iastate.edu/Greenbowe/sections/projectfolder/flashfiles/stoichiometry/acid_base.html Titration Set-Up

  9. Types of Titration • Strong Acid vs. Strong Base

  10. Strong Base vs. Weak Acid A weak acid or base will resist an abrupt change in pH because they show “buffering action” A buffer is a solution resisting a change in pH because they can force the reaction to go in reverse Types of Titration

  11. Video Demo • http://www.youtube.com/watch?v=g8jdCWC10vQ

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