Titration Expt. Overview

• Day 1: You will create a ~0.1 M NaOH solution• Day 2: You will standardize your solution of

NaOH by titrating it with a solid acid, KHP• Purpose: To verify your [NaOH] up to 3 SF• It should be close to 0.100 M NaOH

• Day 3: You will titrate your now known concentration of NaOH with an unknown concentration of HCl• Purpose: To determine the [HCl]

Day 1: Making a NaOH solution• You and your partner will make 250 mL of a ~0.1 M

NaOH solution• How will you do this? What do you need to know?

What equipment do you need?• Remember, M = mol/L• Calculate the mol NaOH necessary g NaOH• Measure g NaOH using a balance and dissolve in

250.0 mL distilled water together in a volumetric flask

• Calculate and record actual [NaOH] in M (mol/L)• Should be close to 0.100 M, but won’t be exact• 3 SF

Day 2: Standardization of NaOH(aq)

• Purpose: To verify your [NaOH] by reacting (titrating) it with an known acid, KHP

Buret w/ base~0.1 M NaOH

Flask w/ acid and PHTH ind.~0.3 g KHP in ~75 mL H2O

Faint pink tinge…Use white paper underneath to see better

(PHTH)

Day 2: Standardization of NaOH(aq)• Purpose: To verify your [NaOH] by reacting

(titrating) it with an known acid, KHP To neutralize… mol H+ = mol OH-

• Acid = ~0.3 g solid KHP (potassium hydrogen phthlate)• mass g KHC8H4O4 (to 3 SF) mol KHP = mol H+

• Recall M = mol/L, so mol OH- = M OH· L OH

therefore… mol H+ = M OH · L OH

• Do one dry run ball park amount NaOH to add• Do at least two good trials, if not three• Average your [NaOH] results

Day 3: Titration of HCl(aq) with NaOH(aq)

• Purpose: To determine unknown [HCl] by reacting (titrating) it with known base, NaOH

Buret w/ base~0.1 M NaOH

Flask w/ acid and ind. Yellow

~ 15 mL of ? M HCl

GreenEndpoint

Use white paper underneath to

see better

BlueOvershoot (too basic)

Bromothymol blue

Day 3: Titration of HCl(aq) with NaOH(aq)

• Purpose: To determine unknown [HCl] by reacting (titrating) it with known base, NaOH

To neutralize… mol H+ = mol OH-

Recall M = mol/L … M H+ · L H+ = M OH- · L OH-

• Do one dry run ball park amount NaOH • Do at least three good trials• Whatever you don’t finish today, you can finish

tomorrow• Average your [HCl] results

Lab Report • Typed (calculations may be hand-written)• Sections

• Overview (3-5 sentences)• Procedure

• Day 1: Making NaOH solution• Day 2: Titration (Standardization) with KHP• Day 3: Titration with HCl

• Data Tables• Show organized data for all three days of expt. (include dry

run data and label as such)• Include related data table with each day’s procedure

• Calculations• Show all calculations (no need to use dry run data)• Include related calculations with each day’s procedure

Written portions should be:• 3rd person• Passive voice• Past tense

Lab Report Organization (/50 pts) • Overview (3-5 sentences)• Day 1: Making NaOH solution

• Procedure• Data table• Calcs

• Day 2: Titration (Standardization) with KHP• Procedure• Data table• Calcs

• Day 3: Titration with HCl• Procedure• Data table• Calcs

strong acid + strong base salt + HOHproduct pH = 7… use bromothymol blueyellow (acid), green (neutral), blue (base)

HCl (aq) + NaOH (aq) NaCl (aq) + HOH (l)[H+] = 0.50 M [OH-] = ? M~ 15 -20 mL VB

Measure both V in expt. (to the nearest 0.00 mL) Trials1. (Dry Run)… calculations unimportant (ball park numbers)2. 3. 4. Calculate [OH-] for trials 2-4 and then average

Strong Acid/Strong Base Titration

pH Equivalence Ptmol H+ = mol OH-

mL of base

HCl + NaOH H2O + NaCl

At this point, everything is water, Na+ and Cl-, so the

pH = 7

EndpointOvershoot

Titrate with Bromthymol Blue

Weak Acid/Strong Base Titration

Weak acid + strong base weak base + HOHproduct pH > 7… use phenolphthalein (PHTH)

clear acidpink base

HCH3COO (aq) + NaOH (aq) NaCH3COO (aq) + HOH (l)(acetic acid, 0.24 M (Na+ (aq) +i.e. vinegar) VB CH3COO-(aq))[H+] = ?~ 3-5 mL

Trials1. (Dry Run)… calculations unimportant (ball park numbers)2. 3. 4.

Equivalence Ptmol H+ = mol OH-

mL of base

At this point, the solution contains water, Na+, and C2H3O2

- , so the pH > 7.

EndpointOvershoot

BUFFERING REGION

HC2H3O2 C2H3O2 - + H+

Weak Acid/Strong Base Titration HC2H3O2 + NaOH H2O + NaC2H3O2

Titrate with Phenolphthalein

pH

Equivalence Ptmol H+ = mol OH-

mL of acid

At this point, the solution contains

water, Cl-, and NH4+,

so the pH < 7.

EndpointOvershoot

NH3 + H+ NH4+

BUFFERING REGION

Weak Base/Strong Acid Titration HCl + NH4OH H2O + NH4Cl

Titrate with Methyl Orange

pH