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Chemisrqy 3:SOME INVESTIGA'TIONS INTO TI-IE CORROSION OF IIION

Ptocedure:

Part I. Reaction of Iron wirlr Variorrs Aqueous Ileagentsa' Place a cleatt, bright nail in each of the nl.i.*r rrrbe.s. .slicle each 'ail care{rrllydown the side to avoid breaking the botton, oft,ir. tesr rube.b. Partially fill eacrr of trre rc.rr rub"*s *irh ;;.';i rn. r"rr"*i,if ,.rg",,,s s. thrtrhe nail is just covered. Your teacher will ,.iLyou which ;. ;i1i,;;rorrps rouse. Allsolutions are 0.lM.

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c' Determine the approxitnate hydrogen iorr corrcenrration o[:eac6 .solutionusing litmus pape'; Flydrion-papei or otrrer iiiai.r.o, soruriorrs. It issufficient 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 anychanges thar have taken place.-(..omparc

1rou,. ,.r,rtrs rvitlr rhose of s...rcle rrrsusing 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 clr.trrs ,:F0.11.4. potassiunr fbrricya'ide, 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- of ,

fe*ous strlfaie solrrtio'. c.rnpare ,hi- ;;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 -'fwo Metars irr colrracLa' Prepare "!!::l.ro1, nrL of agrr-apyrr sorurior,,i, fniluws: Freat arrorrt 200 r'r_.of distilled water t. a gentlJboil.' Remo". irt" iu,,,,., a'cl srir. itr 2 g ofpowdered 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,. ;qir;;;'r"ii;;,,. stir r horougrrry.c. Mrile the agar-agar solution i, .ooiirrg,"1,r.p;. L,,r crearr brighr nairs asshown i. Figure la4- Place one nail on one side of a perri dish or.sr'allbeaker. Bend another nair sharpty *i,h';;;;i,

"i pr;.* arrrr

'race ir on trrr:other side of the dish. Twisr. il.rn pi.."'"r.t irJ rnop.r.,ryirc arourr<J a.rhircl

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Distilled water

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Copper rv[re /' 57 f] Y\1 lf ff/\lt*rfr lf /'\,rl/t,. /

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'<-\\r Zinc slrip

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t*I"Il:ll;#l:',the nailand tighten the wi'e c--oir so rrrat wrrerr trrc rrair i.s

second dish. rugrr' ir rnakes tight co'tact wirrr the wirc. prace trris irr a

Repeat the above procedure using a zinc striP .n a fcrrr*h rrail. lf'a srri, ofzinc is not avairabre, apiece or-orry rin. nr"y rl"l,r".j,.a by fbrcing trre riairthrough the zinc pie.ein ",

r.r.t.*o pfaces. i,r,,.. ,rrir',rair irr rrrc seiorrrlff#lu a's 'show' in Figure jg-i. B" r,,r. tr,";^rir',il .or roucfr o'e

d" $rhen dre agar-agar solution has cooled to lukewaflh, and is still fluicl, ;ro.r ircarefrrlly inro tre petri di.she.s ;;rift" nair.s a.t r,erars aof about 0.5 crn. !'v rrdrrit altq fl)etals are covered to a. ,lepth

e' Make observatio's during the time remaining in dre crass peri.r,. l,racc thc6i't'o toly:t:t(er ."1H;; rru,n *goi,ior,., ,i,.f i,ru. .stoo<l over'igrrt.

khn -,{ Pe tfi dishe.t ***,)r_*_=_--**_/.

Questions and Exercises Figure 38 * I '

l' List the teagents itt Part I wherc no indication of corrosiolr rvas o[r.serverf.2' List the ..ri.nt in part r i;' ;il; {;-;;;;, iri,.r,,"n 'rcorrosi'rr.] -fr',i1""-"ilJffll.';ii"

r"'*ii'"*i !/hat i, ,i'. .'ia-'c;e r Fr.r,v clo yc,tr accorr'4' what did vou observc regarcf itlg the.rcacrions at dre hearJ, trre poi,rt*,r errcr, or at rrrcsharp bend of the n';t *li;tl' *3.. ainru*r.;;, ;i#:st of rhi nair? Acco..t firr rrri.s,in terrns of tbe rnechanicar ir."**, of the nair during its nranufictrrre.

, j ffrfi l',illl, #h;tklt**;il$iklixiltrr i,,,,

',t;t;; ; ;,",e an d,,r,

j1frltm ;f**#iu'i'r.il.r",,ia.,1 an' a cororecr precipitate vrire

: Fi:li:i:Ti:::**mTffi:LJ;im*x,,.,.,in,,r vrr,i.,,,he si,e or

: &nn";:ll.;i" ";'i ;;;;ol'l.*.,ion, r";;;;h;;e in whicrr yo,, obscrvecla9' consult dre E" table irr Appenclix s

"id p'edicr anorrrer',merar that i.s r'ore rea,iry

, ^ $J*;1than iron

'"a *iri p,"t*, ;, ri"l" .";il.,:' %sr your. p...ri.rion'by .,,l0' How does a coating of zinc'rt iron (galva'izecl iron), pro(ecrt ir'' fro' corr.sioniI l' Magnesium metar i"a'r,. ,"*.ori; ptr..J in l;;;i;#;, rrcaters. wrr'i

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