redox titration of bleach due today: 1. redox titration of bleach pre-lab 2. copper reduction formal...
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REDOX TITRATION OF BLEACH
Due Today: 1. Redox Titration of Bleach Pre-Lab
2. Copper Reduction Formal Lab Report
Homework:1. Redox Titration Short Report
2. Gravimetric Analysis of Phosphorus Pre-Lab
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Determine the weight percent of
sodium hypochlorite (NaOCl) in
bleach via redox titration.
OBJECTIVE
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Oxidation-Reduction (Redox) Reaction:
▪Follow the transfer of electrons▪Matched reaction – you cannot have one without the other
KEY TERMS
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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
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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
KEY TERMS
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Preparation of KIO3 Solution:
▪Use 250 mL volumetric flask
▪Be precise!
PROCEDURE NOTES
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Standardization of (Na2S2O3):
▪Rinse the buret with DI water and Na2S2O3 before you titrate
▪PIPETE KIO3 solution▪DO NOT PIPET FROM VOLUMETRIC FLASK!!
▪IMMEDIATELY titrate after KI is added
PROCEDURE NOTES
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▪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
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Titration of Bleach
▪Weigh 2.000g of bleach
▪During the Titration:
▪Immediately titrate when you add KI
▪Look for light yellow color
PROCEDURE NOTES
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▪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!!!!!!!
PROCEDURE NOTES
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Solutions can go down the drain
WASTE
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Sodium Hypochlorite (Bleach)Danger
Skin Irritant
Respiratory Irritant
RISK ASSESSMENT
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CALCULATIONS
flask c volumetriof volume
moles3KIOM
pipettedKIO VM 3
moles
■ Moles KIO3 used in titration:
■ Molarity of KIO3 Solution:
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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
100Bleach of mass
NaOCl mass mass%
■ Mass Percent:
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REDOX EQUATION EXAMPLE
𝐶𝑢𝑆𝑂 4 (𝑎𝑞 )+𝑍𝑛 (𝑠 )→𝑍𝑛𝑆𝑂4 (𝑎𝑞 )+𝐶𝑢(𝑠)
Redox Equation:
1. Make sure your equation is balanced𝐶𝑢𝑆𝑂 4 (𝑎𝑞 )+𝑍𝑛 (𝑠 )→𝑍𝑛𝑆𝑂4 (𝑎𝑞 )+𝐶𝑢(𝑠)
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REDOX EQUATION EXAMPLE
2. Assign Oxidation Numbers
𝐶𝑢𝑆𝑂 4 (𝑎𝑞 )+𝑍𝑛 (𝑠 )→𝑍𝑛𝑆𝑂4 (𝑎𝑞 )+𝐶𝑢(𝑠)Cu : +2S : +4O : -8
Zn: 0 Cu: 0Zn : +2S : +4O : -8
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REDOX EQUATION EXAMPLE
𝐶𝑢𝑆𝑂 4 (𝑎𝑞 )+𝑍𝑛 (𝑠 )→𝑍𝑛𝑆𝑂4 (𝑎𝑞 )+𝐶𝑢(𝑠)
Cu : +2S : +4O : -8
Zn: 0 Cu: 0Zn : +2S : +4O : -8
3. Determine which species is oxidized and reduced
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