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

Determine the weight percent of

sodium hypochlorite (NaOCl) in

bleach via redox titration.

OBJECTIVE

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

KEY TERMS

Preparation of KIO3 Solution:

▪Use 250 mL volumetric flask

▪Be precise!

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

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!!!!!!!

PROCEDURE NOTES

Solutions can go down the drain

WASTE

Sodium Hypochlorite (Bleach)Danger

Skin Irritant

Respiratory Irritant

RISK ASSESSMENT

CALCULATIONS

flask c volumetriof volume

moles3KIOM

pipettedKIO VM 3

moles

■ Moles KIO3 used in titration:

■ Molarity of KIO3 Solution:

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:

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)

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

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