Zinc

7/17/2019 Zinc

http://slidepdf.com/reader/full/zinc563db909550346aa9a9965cc 1/20

“Statistical Analysis of

Zinc Coated Washers”

Purpose of the ExperimentDetermine how many centimeters

of zinc and layers of zinc atoms

are present on the surface of agalvanized steel washer.

7/17/2019 Zinc


What is Corrosion?

Natural process of deterioration of metals andalloys in a corrosive environment

!esults in an actual decrease in the thic"ness or

si#e of the ori$inal metallic structure

“A poorly protected

surface can %e a %i$

mista"e & So don't

compromise

(alvani#e)” *

Corroded Galvanized

7/17/2019 Zinc


The most common corrosion reaction is the

rusting of iron in water

+ ,e - . /01 - 2 10 3&&4 + ,e51/62

The oxidation portion of the reaction results

in the actual loss of metal,e 3&&4 ,e-0 - 0 e& Step one 5176

,e-0 3&&4 ,e-2 - e& Step t8o 5176

,e 3&&4 ,e-2

- 2 e&

1verall 1xidation half&reaction

The reduction portion of the reaction

drives the process of corrosion

10 - 0 /09 - + e&

3&&4 + 1/&

!eduction half&reaction

7/17/2019 Zinc


What is (alvani#in$?

The process of

galvanizing consists

of coating metals,

such as iron, with a

thin protective layer ofzinc.

The zinc layer

provides protection to

the metal from

corrosion.

:efore ; After

/ot <ip (alvani#in$

7/17/2019 Zinc


=he steel is protected %y the

surroundin$ #inc even if it is scratched

Cathodic Protection

An anodic layer> such as chromium>

nic"el> copper> or paint> allo8s corrosion to

$ro8 under its layer 8hen it is scratched

Anodic Protection

7/17/2019 Zinc


Zinc coatings prevent corrosion of the protected metal by forming a

barrier, and by acting as a sacrificial anode if this barrier is damaged.

hen exposed to the atmosphere,

zinc reacts with oxygen to form

zinc oxide, which further reacts

with water molecules in the air to

form zinc hydroxide.

!inally zinc hydroxide reacts with

carbon dioxide in the atmosphere

to yield a thin, impermeable,

tenacious and "uite insoluble dull

gray layer of zinc carbonate which

adheres extremely well to the

underlying zinc, so protecting it

from further corrosion.

/o8 <oes Zinc Protect =he nderlyin$ @ron Surface?

http#$$www.videopediaworld.com$video$%&&'($Deconstruction)*uilding)a)+ouse)Galvanizing)ails

http://www.videopediaworld.com/video/41136/Deconstruction-Building-a-House-Galvanizing-Nails

http://www.videopediaworld.com/video/41136/Deconstruction-Building-a-House-Galvanizing-Nails

7/17/2019 Zinc


These potentials indicate the relative thermodynamic

tendency for the indicated half)reaction to occur.

The oxidation of zinc is more li-ely than the oxidation of iron.

Zn 3&&4 Zn-0 - 0 e B E B9D.2 volts

,e 3&&4 ,e-0

- 0 e B

E –

9+9 volts

7/17/2019 Zinc


&. Get washers, filter paper / 0ernier calipers from the stoc- room.

1. 2eep washers in the same order during the experiment. This can be done

by writing numbers on the filter paper.'. 3ecord on datasheet the inner and outer diameters and the height of each

washer to the nearest 4.4& cm.

Zinc Coatin$ Experiment

5uter diameter

6nner diameter +eight

Fernier Calipers

httpsGHH888youtu%ecomH8atch?vZNoWW8.FI9

https://www.youtube.com/watch?v=ZUNoWWw6V10

https://www.youtube.com/watch?v=ZUNoWWw6V10

7/17/2019 Zinc


%. eigh and record the mass of each washer to the nearest 4.44& gram.

78a-ing sure to weigh the washers on the same balance each time.9

To eigh# :lace filter paper on the balance. Tare. 7;et the balance to zero.9

:lace the washer on the filter paper. 3ecord weight.


7/17/2019 Zinc


. 6n an &44 ml bea-er, get <(4 ml of '8 +Cl.

(. =ttach copper wire to one of the zinc washers.

>. Dip the washer in the bea-er of +Cl and observe the reaction.

Zn 7s9 ? 1 +Cl J +17g9 ? ZnCl1 7a"9


@. =llow the reaction to continue until bubbling stops, approximately A4 sec.

7The surface will change from shiny silver to a dull gray.9

A. 3emove the washer from the acid and rinse with distilled water over a waste

bea-er.

7/17/2019 Zinc


&4. Bse paper towel to dry the washer.&&. :lace dried washer on corresponding

filter paper.

&1. eigh the washer on the same

balance used before.

&'. 3ecord the mass.

&%. 3epeat the same procedure for

other washers.

&.Dispose the washers in the used

solids container.

&(. Dispose the exhausted +Cl in the

li"uid waste container.


7/17/2019 Zinc


&. 0olume of Zinc Coating 8ass of asher 3eacted $ Density of Zinc

where dzinc>.&% g$cm'

1. Total ;urface =rea of Zinc Total ;urface =rea of asher

'. Thic-ness of Zinc Coating 0olume of Zinc Coating $ Total ;urface =rea of Zinc

%. Thic-ness of Zinc in =toms, where Diameter of Zn atom 1(@ pm, & m &4&1 pm

. rror =nalysis / ;tatistics# !ind the 8ean 7=verage9, ;tandard Deviation andConfidence 6nterval 7A@E9 for 0olume, ;urface =rea and Thic-ness of Zinc in =toms.

+eight of

the washer,

h

Di# 6nner diameter

Do# 5uter diameter

Total ;urface =rea 1π(r 41)r i19? 1πr 4h ? 1πr ih

where r radius F diameter

Calculations

K individual measurements for each 8asher

7/17/2019 Zinc


AccurateThe average isaccurate but

not precise.

PreciseThe average is

precise but

not accurate.

Accurate ; PreciseThe average is bothaccurate and precise.

Error Analysis of Accuracy ; Precision

Systematic or <eterminate ErrorsG ;hifts in the measured values from thetrue values which reduces the accuracy of a result. 7=n example of a

systematic error is misreading a graduated cylinder9.

!andom or @ndeterminate ErrorsG ;hifts in the measured values from the

true values which influences the precision or scatter of the result. 7xamples

of random errors might be the imprecision among multiple readings9.

7/17/2019 Zinc


Percent Error [ ] 100% ×

−=

theor

obstheor

X

X X E

The percent error is the absolute value of the "uantity of the theoretical

value minus the observed value divided by the theoretical value andmultiplied by one hundred.

<etermination of AccuracyThe accuracy can be determined by loo-ing at the difference between

the expected 7theoretical9 average and the experimental 7observed9

average.

=he Avera$e or Lean Falue 5x%ar 6

The avera$e or mean of a set of numbers, X i , is found by adding the

numbers and dividing by the number of values, N .

=hus the avera$e of 2> K> D> 2> and K 02 H K or +.

N

X

X

N

ii

∑== 1 Ʃ means sumH

7/17/2019 Zinc


*Estimate of the Standard Deviation

The standard deviation, a measure of the spread of N values, X i ,

about the average value, σ, a measure of precision, is given by,

1

)(1

2

−

−

=

∑=

N

X X

s

N

i

i

=he Standard <eviation

N

X

N

i

i∑=

−

= 1

2)( µ

σ

6f the number of values, N > is small, i.e., if N I '4, an estimate

of the standard deviation, s, is given by,

The standard deviation is used for large populations, J '4.

We 8ill %e usin$ the

Estimate of the

Standard <eviation

%ecause 8e have a

small data set

7/17/2019 Zinc


Confidence Limit

X ± t σ

N

Student’st-factors are given in tablesfor different probabilities. (Note: The

table in your book is onpage 56.)

X

wheret isStudent’st-factor.

At the90 % confidence limit, 90

times out of 100 the true value willbe within±1.64σ of the experimentalresults.

The confidence limit defines an

interval about the average that mostlikely contains µ .

7/17/2019 Zinc


(raphs of the Folume> Surface Area and =hic"ness of Zinc in atoms

:age > K1# 6n xcel 7or any program that will ma-e graphs9,

ma-e ' column graphs where the washers and the average

washer are listed on the x axis of all three. 5n the y axis of graph

K& show their volumesL on graph K1 their surface areasL and, on

graph K' their thic-nesses. Do not forget to include units.

(raph MI

@mportant NoteG Each student must ma"e their o8n $raphs @f %oth la% partners su%mit

identical $raphs> then each la% partner 8ill receive a #ero score for the $raphs or 9HI0 pts

7/17/2019 Zinc


(raph M0

(raph M2

7/17/2019 Zinc


/a#ards for Zinc Experiment!eactantG ' 8 +Cl is a corrosive strong acid.

76f spilled, a+C5' will be used to neutralize.9

ProductG +ydrogen gas is flammable.

Stoc"room @nformation:efore Experiment Chec" 1utG

Zinc coated washers & set of 0ernier calipersM

pieces of filter paper & piece of Copper wireM

!eturn to Stoc"roomGI set of Fernier calipers

I piece of Copper 8ire

Place in “sed Solids” %uc"etG washers with Zinc coating removed

pieces of filter paper

After ExperimentG

Pour in “Zinc a%” liOuid 8aste car%oyG

Bsed +Cl with Zn1? / 3insings

Neftover +Cl

7/17/2019 Zinc


Next Wee" & ,e%ruary I9&I0!eadG Determining the mpirical !ormula of

Copper Chloride 7Text pp. >>)A%9

!eadG 5xidation $ 3eduction 7:ac-et (A)>@9

!eadG Dimensional =nalysis ;ets K1 / K' 7Text pp. 1%)1@9

=urn&@nG &.9 Dimensional =nalysis ;ets K1 / K' 7all problems9

1.9 Zinc pp. ()> 7This includes the :ost)Nab9.

ote# K1 7p >9 ) ou need to ma-e 2 $raphs)

ote# *ottom p( O Pou need to ma-e

a separate calculations pa$e for Med calculations.

Zinc

Documents

zinc layer

oxidation of zinc

zinc washers

underlying zinc

zinc hydroxide

centimeters of zinc

zinc oxide

thesurrounding zinc