Experiment 8

Question 1

Goal

Answer 1

Determine oxidizing capacity of commercial bleach

Question 2

Most common active ingredient

Answer 2

Hypochlorite ion (ClO-)

Question 3

How does hypochlorite ion work

Answer 3

As an oxidizing agent (LEO) removes electrons from the stain

Question 4

Removing electrons from stain =

Answer 4

Destroying substances that absorb visible light

Question 5

When does material become whiter

Answer 5

when light absorbing material has been destroyed (light no longer being absorbed)

Question 6

How many redox are we using

Answer 6

2

Question 7

Eq 1: what is in excess

Answer 7

Potassium Iodide (KI)

Question 8

Eq 2: excess/acid

Answer 8

H+ in excess, acid is H2S04 (sulfuric acid)

Question 9

How is I2 produced in solution determined?

Answer 9

Through titration with a standardized thiosulfate solution

Question 10

Mole ratio at equivalence point of titration

Answer 10

(1 mol ClO-) : (2 mol S2O3 2-)

Question 11

Titrating with

Answer 11

Na2S203

Question 12

Amt. bleach

Answer 12

1-1.2 grams

Question 13

Colour change after adding 2g KI

Answer 13

NONE

Question 14

Colour change after adding 10ml H2S04

Answer 14

BROWN (indicates presence of iodine)

Question 15

Titrate with Na2S2O3 until….

Answer 15

Brown to pale yellow

Question 16

After pale yellow…add:

Answer 16

5 drops of starch indicator

Question 17

Endpoint:

Answer 17

found drop by drop after adding starch….black JUST disappears

Question 18

Moles thiosulfate

Answer 18

n=cv (with titer volumes and given conc of tiosulfate)

Question 19

Moles hypochlorite

Answer 19

2 th : 1 hc

Question 20

Wght% sodium hypochlorite

Answer 20

(mass sodium hypochlorite / mass bleach) x100

Question 21

Mean wt.percent

Answer 21

from all 3 trials / 3

Question 22

Standard deviation

Answer 22

(wt-mean) - summed
sum / n-1
sqr rt

Question 23

Relative stan dev

Answer 23

sd/mean