Presentation on theme: "Burette clamp ring stand burette erlenmeyer flask Titration."— Presentation transcript:
burette clamp ring stand burette erlenmeyer flask Titration
Calculate the concentration or volume of an acid or base from the concentration and volume of an acid or base required for neutralization. Using a standardized acid or base, determine the concentration of an unknown base or acid. Additional KEY Terms standard solutionequivalence point end pointtitration
Titration – quantitative chemical reaction. unknown reacted with a standard solution used to find [ ] of unknown solution Standard solution – solution of known concentration which is compared to unknown. **pH does not indicate concentration because weak acids/bases do not dissociate completely. HA + BOH BA + H 2 O 2.0 M ???
ring stand burette clamp erlenmeyer flask burette Titration Apparatus buret
Equivalence point amount of standard needed to react (to completion) with the unknown sample to End point point in the reaction when indicator turns colour moles H + = moles OH - Eq. point - defined by balanced reaction (pH = 7) Endpoint - determined by the choice of indicator
Goal is to pick the indicator with an end point at the same pH as the equivalence piont
1.Measured amount of unknown concentration is added to the flask. 2.An appropriate indicator is added to the unknown. 3. Measured amount of known concentration is added slowly from the buret. 4. The titration is stopped when a colour change has occurred (end point). 5.Concentration of the acid is calculated. Titration can also be preformed the other way - the standard in the flask, and the unknown in the buret
Determine the concentration of a hydrochloric acid solution using a 0.100 mol/L solution of NaOH Indicator - phenolphthalein (endpoint turns pink) HCl (aq) + NaOH (aq) NaCl (aq) + H 2 O (l)
1. Calculate the moles of base used: 1:1 ratio0.001383 moles of HCl = 0.001383 mol NaOH 0.100 mol0.01383 L 1 L = 0.121 M HCl 0.001383 mol 0.01144 L 2. Use stoich to determine moles of acid used: 3. Calculate unknown value.
Calculate the concentration of hydrochloric acid, if 25.00 mL is just neutralized by 40.00 ml of a 0.150 mol/L sodium hydroxide solution. HCl (aq) + NaOH (aq) 1:1 ratio0.00600 moles of HCl = 0.006 moles NaOH 0.150 mol0.04 L 1 L = 0.240 M HCl 0.006 mol 0.025 L NaCl (aq) + H 2 O (l)
What volume of a 0.250 mol/L solution of carbonic acid is needed to neutralize 30.0 g of sodium hydroxide. H 2 CO 3(aq) + 2 NaOH (aq) = 0.750 moles NaOH 30.0 g1 mole 40.0 g Molar mass of NaOH = 40.0 g Na 2 CO 3(aq) + 2 H 2 O (l) 1:2 ratio0.375 moles of H 2 CO 3
1.5 L of 0.250 mol/L H 2 CO 3 will neutralize 30.0 g of NaOH = 0.375 moles H 2 CO 3 0.750 mol1 H 2 CO 3 2 NaOH = 1.5 L H 2 CO 3 0.375 mol1 L 0.250 mol 1:2 ratio
Plotting pH values during a titration gives a titration curve. Type of curve produced accounts for 2 classes of titrations: 1. Strong acid titrated with strong base. Strong base titrated with strong acid. 2. Weak acid titrated with strong base. Weak base titrated with strong acid.
SB - SA Strong w/ Strong titrations produce well defined, steep s-curves
Eq point is the centre of the steepest portion of the curve Eq point is at a pH = 7 SA - SB
WA - SB Strong w/ weak titrations produce sloppy s-curves
WB - SA Eq point not at pH = 7 due to secondary reaction with acidic or basic salt
CAN YOU / HAVE YOU? Calculate the concentration or volume of an acid or base from the concentration and volume of an acid or base required for neutralization. Using a standardized acid or base, determine the concentration of an unknown base or acid. Additional KEY Terms standard solutionequivalence point end pointtitration