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Titration

Titration. Acid–Base Titration. The concentration of an acid especially a weak one or a weak base in water is difficult to measure directly. But we can calculate the concentration from the results of titration. A titration is a carefully controlled neutralization reaction.

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Titration

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  1. Titration

  2. Acid–Base Titration • The concentration of an acid especially a weak one or a weak base in water is difficult to measure directly. • But we can calculate the concentration from the results of titration. • A titration is a carefully controlled neutralization reaction. • Titration is a lab technique for measuring the concentration of an unknown acid or base

  3. Acid–Base Titration • The average titration involves three components 1. An acid or base of unknown concentration 2. You need a standard solution or titrant • A standard is a solution of known concentration • The known solution is also called the titrant. 3. An indicator – Methyl Red

  4. Acid–Base Titration • The purpose of the indicator is used to indicate when the acid and base ions are equal • Let’s the person performing the titration know when neutralization has occurred • Methyl red is a very common indicator chosen • It undergoes a color change at a pH of about 4.4 • Red in acid • Yellow in base

  5. Strong Acid/Base Titration: pKa=pH

  6. Acid–Base Titration • In titration, the standard is slowly added to the unknown solution • As the 2 solutions mix, the acid in one neutralizes the base in the other • Eventually, enough standard solution is added to neutralize all of the acid or base in the unknown solution. • Indicator changes color

  7. Procedure for Titration • The point at which the indicator changes color is called the equivalency point of the titration. • If the indicator is chosen correctly the end point should be very close to the equivalence point.

  8. Procedure for Titration • Therefore, at approximately the end point of a titration the total moles of H+ donated by the acid is equal to the total moles of H+ accepted by the base. • We call these molar equivalences (stoichiometric equivalences) • Calculate moles of standard solution • Calculate moles of unknown (stoichiometry) • Calculate concentration of unknown *Remember: (conc)(vol in L) = moles

  9. http://www.youtube.com/watch?v=sFpFCPTDv2w

  10. Sample Problem Solutions of NaOH are used to unclog drains. A 43.0 ml volume of NaOH was titrated with 32.0 ml of .100M HCl. What is the molar concentration of the NaOH solution?

  11. Sample Problem 200 ml of a 0.1 M solution of sodium hydroxide was needed to neutralize 125 ml of a sulfuric acid solution. What concentration was the sulfuric acid solution?

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