Due Today:
1 . Redox
Titration of
Bleach Pre-Lab
REDOX TITRATION
OF BLEACH
2. Copper
Reduction Formal
Lab Report
Homework:
1. Redox Titration
Short Report
2. Gravimetric
Analysis of
Phosphorus PreLab
OBJECTIVE

Determine the weight percent of sodium
hypochlorite (NaOCl) in bleach via redox
titration.
KEY TERMS
Oxidation-Reduction (Redox) Reaction:
▪ Follow the transfer of electrons
▪ Matched reaction – you cannot have one without
the other
KEY TERMS
Titration – process of reacting a solution of
unknown concentration with a solution of a
known concentration until the reaction is
JUST complete
▪ All reactants are limiting
KEY TERMS
Equivalence Point – equal quantities of
opposite solutions exist
▪ For acid/base titrations:
Moles of acid = Moles of base
For redox titrations, you must you the reaction
equation to determine moles
PROCEDURE NOTES
Preparation of KIO 3 Solution:
▪ Use 250 mL volumetric flask
▪ Be precise!
PROCEDURE NOTES
 Standardization of (Na 2 S 2 O 3 ) :
▪ Rinse the buret with DI water and Na 2S 2O 3 before
you titrate
▪ PIPETE KIO3 solution
▪ DO NOT PIPET FROM VOLUMETRIC FLASK!!
▪ IMMEDIATELY titrate after KI is added
PROCEDURE NOTES
▪ During the Titration:
▪ Look for light yellow color
▪ Add starch
▪ Blue/Black
▪ Titrate until clear
▪ 1-5 drops
▪ 3 good trials
▪ Molarities within 5% of average
PROCEDURE NOTES
Titration of Bleach
▪ Weigh 2.000g of bleach
▪ During the Titration:
▪ Immediately titrate when you add KI
▪ Look for light yellow color
PROCEDURE NOTES
▪ Add starch
▪ Blue/Black
▪ Titrate until clear
▪ 1-5 drops
▪ 3 good trials
▪ Molarities within 5% of average
▪ RECORD THE REPORTED MASS NaOCl FROM THE
BLEACH BOTTLE!!!!!!!
WASTE
Solutions can go down the drain
RISK ASSESSMENT
Sodium Hypochlorite
(Bleach)
 Danger
 Skin Irritant
 Respiratory Irritant
CALCULATIONS
■ Molarity of KIO3 Solution:
M KIO3
moles

volume of volumetri c flask
■ Moles KIO3 used in titration:
moles  M KIO3  V pipetted
CALCULATIONS
■ Moles of Na2S2O3 used in titration:
 You will need to use stoichiometry
 HINT look for a relationship between the two
equations on page 44
■ Mass Percent:
mass NaOCl
mass% 
100
mass of Bleach
REDOX EQUATION EXAMPLE
Redox Equation:
𝐶𝑢𝑆𝑂4 𝑎𝑞 + 𝑍𝑛 𝑠 → 𝑍𝑛𝑆𝑂4 𝑎𝑞 + 𝐶𝑢(𝑠)
1. Make sure your equation is balanced
𝐶𝑢𝑆𝑂4 𝑎𝑞 + 𝑍𝑛 𝑠 → 𝑍𝑛𝑆𝑂4 𝑎𝑞 + 𝐶𝑢(𝑠)
REDOX EQUATION EXAMPLE
2. Assign Oxidation Numbers
𝐶𝑢𝑆𝑂4 𝑎𝑞 + 𝑍𝑛 𝑠 → 𝑍𝑛𝑆𝑂4 𝑎𝑞 + 𝐶𝑢(𝑠)
Cu : +2
S : +4
O : -8
Zn: 0
Zn : +2
S : +4
O : -8
Cu: 0
REDOX EQUATION EXAMPLE
3. Determine which species is oxidized and reduced
𝐶𝑢𝑆𝑂4 𝑎𝑞 + 𝑍𝑛 𝑠 → 𝑍𝑛𝑆𝑂4 𝑎𝑞 + 𝐶𝑢(𝑠)
Cu : +2
S : +4
O : -8
Zn: 0
Zn : +2
S : +4
O : -8
Zn: 0→+2 loss of electrons
Zinc is oxidized and is the reducing agent
Cu: +2→0 gain electrons
Copper is reduced and is the oxidizing agent
Cu: 0