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Chemisrqy 3:
SOME INVESTIGA'TIONS INTO TI-IE
CORROSION OF IIION
Ptocedure:
Part I. Reaction of Iron wirlr Variorrs Aqueous Ileagents
a' Place a cleatt, bright nail in each of the nl.i.*r rrrbe.s. .slicle each
care{rrlly
down the side to avoid breaking the botton, 'ail
oft,ir. tesr rube.
b. Partially fill eacrr of trre rc.rr rub"*s *irh ;;.';i rn. r"rr"*i,if ,.rg",,,s s. thrt
rhe nail is just covered. Your teacher
use. Allsolutions are 0.lM.
will ,.iLyou which ;. ;i1i,;;rorrps ro
KOI"I
[r,PQ,
&€9,*. l&s"!I
HNO
Distilled water
c' Determine the approxitnate hydrogen iorr
corrcenrration o[:eac6 .solution
using litmus pape'; Flydrion-papei or otrrer
iiiai.r.o, soruriorrs. It is
sufficient to recotd siilrply *liutir.ith.
r;il;; is acidic, basic, or neurral.
Go on to part II.
d' Allow the nails t'sta.nd overnight in the solutions. observe
and recor4 any
changes thar have taken place.-(..omparc
1rou,. ,.r,rtrs rvitlr rhose of s...rcle rrrs
using the_1ther sets oFreagenrs. Recorcr
d-,.i,1 ,=rrrrr rro,,f *iirr,-r",,*;"
tabular fornr.
e' After the soltrtiotrs have stoocl nvernigh_t, arld o'c or rwo
. potassiunr fbrricya'ide,
clr.trrs ,:F0.11.4
KFc(CN)., i"l,;.1, conrai^$ rhe ir:rrr.s l(, ;r.cf
^ f"J9N)0."', to each solution ,n,l o'dse*. ,r;r,-l,r,,g*.
f' Add one
4lop oro.l M potassiurn fbrricyani<Je solution r' abour I rnl-
fe*ous strlfaie solrrtio'. c.rnpare ,hi- of ,
;;J;o il,r, obtairrerJ when rlre
. potassium ferricyanide was adied to
the various sol,rtion,, .",,rri,,i"* ,r,,;l*.
vhat concrr-rsio's can be made nor" ii," ,;;;;rr;
in step e?
Part II. 'Reactions invorving Merar coupres
a'Prepare
-'fwo Metars irr colrracL
nrL of agrr-apyrr sorurior,,i, fniluws:
"!!::l.ro1,
of distilled water t. a gentlJboil.' Remo".
Freat arrorrt 200 r'r_.
irt" iu,,,,., a'cl srir. itr 2 g of
powdered agar-agar' dontirtrre the
heating."a .t1i1 rrntil the :rgar- i.s clispersecl.
b. Add about iO arlp, of 0..1M potassiurn feiri.yanide
ancl5 drops o[0.]%,
phenolphtharein indic*ror ro ,t,.
c.
;qir;;;'r"ii;;,,. stir r horougrrry.
Mrile the agar-agar solution i, .ooiirrg,"1,r.p;.
L,,r crearr brighr nairs as
shown i.
Figure la4- Place one nail on one
side of a perri dish or.sr'all
beaker. Bend another nair sharpty *i,h';;;;i,
pr;.* arrrr ir on trrr:
other side of the dish. Twisr. il.rn pi.."'"r.t "i
irJ rnop.r.,ryirc arourr<J a.rhircl
'race
,t
ii
1i
t ,.1

2. i
u
i
.,1 t
I
t*I"Il:ll;#l:',the nailand tighten the wirrr
rugrr' ir rnakes tight co'tact
wi'e c--oir so rrrat wrrerr trrc rrair
prace trris
i.s
second dish. the wirc. irr a
Repeat the above procedure
using a zinc striP .n a fcrrr*h rrail.
zinc is not avairabre, apiece
or-orry rin. nr"y rl"l,r".j,.a by fbrcing srri, oflf'a
through the zinc pie.ein
r.r.t.*o pfaces. i,r,,.. ,rrir',rair irr rrrc trre riair
a's 'show' in Figure jg-i.
", seiorrrl
ff#lu B" r,,r. tr,";^rir',il .or roucfr
o'e
d" $rhen dre agar-agar solution has
cooled to lukewaflh, and
carefrrlly inro tre petri di.she.s is still fluicl,
of about 0.5 crn.
;;rift"
!'v nair.s a.t r,erars a covered to ;ro.r ir
rrdrrit altq fl)etals
are a. ,lepth
e' Make observatio's during the time
remaining in dre crass peri.r,.
6i't'o toly:t:t(er ."1H;; rru,n *goi,ior,., ,i,.f i,ru.
l,racc thc
.stoo<l over'igrrt.
'<-r Zinc slrip
ttt,/
t-
Copper
1 57 f] Y
/'
rv[re
lt* lf ff/
57
t,.
rfr lf
il
',rl/ I
/
khn 1. /
-,{ Pe tfi dishe.t ***,)r_*_=_--**_/. ,/
! l" |
Figure 38 * I
Questions and Exercises '
l' List the teagents itt Part wherc
2' List the ..ri.nt in part rI i;' ;il; no indication of corrosiolr rvas o[r.serverf.
{;-;;;;, iri,.r,,"n
r"'*ii'"*i !/hat i, ,i'. .'ia-'c;e 'rcorrosi'rr.
]
4' -fr',i1""-"ilJffll.';ii" itlg
what did vou observc regarcf
r Fr.r,v clo yc,tr accorr'
the.rcacrions at dre hearJ,
sharp bend of the n';t
*li;tl'
in terrns of tbe rnechanicar
*3.. ainru*r.;;, ;i#:st of poi,rt*,r errcr, or at rrrc
trre
ir."**, rhi nair? Acco..t firr rrri.s,
,
j ffrfi l',illl, #h;tklt**;il$iklixiltrr of the nair during its nranufictrrre.
i,,,,
',t;t;;
; ;,",e an d,,r,
j1frltm ;f**#iu'i'r.il.r",,ia.,1 an' a cororecr precipitate vrire
I
: Fi:li:i:Ti:::**mTffi:LJ;im*x,,.,.,in,,r
;;;;ol'l.*.,ion,
vrr,i.,,,he si,e or
r";;;;h;;e
: consult table ";'i
9' &nn";:ll.;i" dre E" irr Appenclix s
in whicrr yo,, obscrvecla I
p'edicr anorrrer',merar
iron "id that i.s r'ore rea,iry
'"a *iri p,"t*, ;, ri"l" .";il.,:' %sr your. p...ri.rion'by
I
,
^ $J*;1than
l0' How does a coating of
zinc'rt iron (galva'izecl iron),
.,,
I l' Magnesium metar
i"a'r,. ,"*.ori; ptr..J in l;;;i;#;, ir'' fro' corr.sioni
fi
pro(ecrt
rrcaters. wrr'i E
I
I
,*