1. 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
Redox Titration OF bleach

2. Objective
Determine the weight percent of sodium hypochlorite (NaOCl) in bleach via redox titration.

3. Key Terms Oxidation-Reduction (Redox) Reaction:
Follow the transfer of electrons
Matched reaction – you cannot have one without the other

4. 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

5. 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

6. Procedure Notes Preparation of KIO3 Solution:
Use 250 mL volumetric flask
Be precise!

7. Procedure Notes 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

8. 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

9. Procedure Notes Titration of Bleach During the Titration:
Weigh 2.000g of bleach
During the Titration:
Immediately titrate when you add KI
Look for light yellow color

10. Procedure Notes Add starch Titrate until clear 3 good trials
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!!!!!!!

11. Waste
Solutions can go down the drain

12. Risk assessment Sodium Hypochlorite (Bleach) Danger Skin Irritant
Respiratory Irritant

13. calculations
Molarity of KIO3 Solution:
Moles KIO3 used in titration:

14. calculations Mass Percent: 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:

15. Redox Equation Example
𝐶𝑢𝑆𝑂 4 𝑎𝑞 +𝑍𝑛 𝑠 → 𝑍𝑛𝑆𝑂 4 𝑎𝑞 +𝐶𝑢(𝑠)
1. Make sure your equation is balanced
𝐶𝑢𝑆𝑂 4 𝑎𝑞 +𝑍𝑛 𝑠 → 𝑍𝑛𝑆𝑂 4 𝑎𝑞 +𝐶𝑢(𝑠)

16. Redox equation example
2. Assign Oxidation Numbers
𝐶𝑢𝑆𝑂 4 𝑎𝑞 +𝑍𝑛 𝑠 → 𝑍𝑛𝑆𝑂 4 𝑎𝑞 +𝐶𝑢(𝑠)
Cu : +2
S : +4
O : -8
Zn: 0
Cu: 0
Zn : +2

17. Redox equation example
3. Determine which species is oxidized and reduced
𝐶𝑢𝑆𝑂 4 𝑎𝑞 +𝑍𝑛 𝑠 → 𝑍𝑛𝑆𝑂 4 𝑎𝑞 +𝐶𝑢(𝑠)
Cu : +2
S : +4
O : -8
Zn: 0
Cu: 0
Zn : +2
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