Titration burette clamp ring stand burette erlenmeyer flask

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 solution equivalence point end point titration

HA + BOH  BA + H2O 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. HA + BOH  BA + H2O 2.0 M ??? **pH does not indicate concentration because weak acids/bases do not dissociate completely.

Acid / Base Titration Apparatus burette clamp burette buret ring stand erlenmeyer flask

amount of standard needed to neutralize the unknown sample Equivalence point amount of standard needed to neutralize the unknown sample moles H+ = moles OH- (pH = 7) Eq. point - defined by balanced reaction End point point in the reaction when indicator turns colour. 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

Measured amount of unknown concentration is added to the flask. 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). Concentration of the acid is calculated. **Titration can also be preformed with a calculated volume of standard in the flask, and the unknown in the buret.

Calculate the concentration of hydrochloric acid, if 25 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. NaCl(aq) + H2O(l) HCl(aq) + NaOH(aq) 0.150 mol 0.04 L = 0.006 moles NaOH 1 L 1:1 ratio 0.00600 moles of HCl 0.006 mol = 0.240 M HCl 0.025 L

What volume of a 0.250 mol/L solution of carbonic acid is needed to neutralize 30.0 g of sodium hydroxide. H2CO3(aq) + 2 NaOH(aq) Na2CO3(aq) + 2 H2O(l) Molar mass of NaOH = 40.0 g 30.0 g 1 mole = 0.750 moles NaOH 40.0 g 1:2 ratio 0.375 moles of H2CO3

1.5 L of 0.250 mol/L H2CO3 will neutralize 1:2 ratio 0.750 mol 1 H2CO3 = 0.375 moles H2CO3 2 NaOH 0.375 mol 1 L = 1.5 L H2CO3 0.250 mol 1.5 L of 0.250 mol/L H2CO3 will neutralize 30.0 g of NaOH

HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l) 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) + H2O(l)

HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l) 1. Calculate the moles of base used: 0.100 mol 0.01383 L = 0.001383 mol NaOH 1 L 2. Use stoich to determine moles of acid used: 1:1 ratio 0.001383 moles of HCl 3. Calculate unknown value. 0.001383 mol = 0.121 M HCl 0.01144 L

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

SA - SB Eq point is the centre of the steepest portion of the curve Eq point is at a pH = 7

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 solution equivalence point end point titration