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Understanding Acid–Base Titration Techniques

Learn how titration is used to determine the concentration of acids and bases. Find out about indicators, equivalence points, and calculating unknown concentrations. Discover practical examples and step-by-step procedures.

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Understanding Acid–Base Titration Techniques

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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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