Presentation on theme: "Titrations......help you see neutralization reactions. Acid and base react to form salt and water....determine concentration of a solution by reacting."— Presentation transcript:
Titrations......help you see neutralization reactions. Acid and base react to form salt and water....determine concentration of a solution by reacting it with a solution with a known concentration.
Types of Titrations Strong Acid with Strong Base Strong Base with Strong Acid Weak Acid with Strong Base Weak Base with Strong Acid Weak Acid with Weak Base
Standard Procedure Prepare standard (titrating solution): it is of known concentration Exactly mass This information will be crucial to all other calculations. Rinse buret So there is no contamination from other substances. Fill buret 2. Unknown: in beaker or flask beneath buret indicator is added Known volumes of standard are added to it.
3. Record data... either volume of standard Time pH Continue until you reach the stoichiometric point: Moles H + from acid = moles OH - from base. Stoichiometric point is the equivalence point pH = pKa End point – one drop of base beyond stoichiometric/equivalence point; color changed; on graph:midpoint of most vertical part of graph = exact midpoint; rate of pH diminishes; 4. REPEAT
Vocabulary equivalence point - when the moles of acid or base added equals the moles of acid or base which are present midpoint - when the moles of acid or base added is 1/2 the moles of acid or base which are present indicator - a dye used to indicate when the reaction is complete. It changes color at the equivalence point.
Important Regions At time = 0, before the titration begins Before the equivalence point At the midpoint At the equivalence point After the equivalence point
Standardizing a Solution... Why is there a need to standardize NaOH? Mole ratio between KHP and NaOH should be 1:1 (at equivalence point of titration)
Strong Acid / Strong Base
Assume 100% ionized in aqueous solution.
Compare Weak/Strong Acid
Diprotic Acid Graph shows a steep rise or endpoint for each of the protons in the acid.