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 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 ratio moles of HCl = mol NaOH mol L 1 L = M HCl mol L 2. Use stoich to determine moles of acid used: 3. Calculate unknown value.

Calculate the concentration of hydrochloric acid, if mL is just neutralized by ml of a mol/L sodium hydroxide solution. HCl (aq) + NaOH (aq) 1:1 ratio moles of HCl = moles NaOH mol0.04 L 1 L = M HCl mol L NaCl (aq) + H 2 O (l)

What volume of a mol/L solution of carbonic acid is needed to neutralize 30.0 g of sodium hydroxide. H 2 CO 3(aq) + 2 NaOH (aq) = 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 mol/L H 2 CO 3 will neutralize 30.0 g of NaOH = moles H 2 CO mol1 H 2 CO 3 2 NaOH = 1.5 L H 2 CO mol1 L mol 1:2 ratio

Titration Curves

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