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]
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 - PowerPoint PPT Presentation
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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
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)