sentidcorr€ct.efcr toFIEM.sirnple

,etweenrimen-. coeffi-I s t o a 'quation; '

o thesclumber

imental

d wateris affect

ruld actr in this

lnesium.Ie.gram

of mag-

d in the

4-5

---ffii

Mass F-elationships in Chemical Reactions

GENERAL DISCUSSIONIn general, we can saY that a r'eaction will go

to completion (be quanritadve)'if one of the rcact'

ants is completely consumed by the reaction-

There, are several wayr that a reactant may be

consurned. This will occur if (a) a precipitate is

Ib*tgi, 0) a ,*eakly dissociated mbstance such

as water or a weak acid is formed, and (c) a gas

(volatile substance) is fonnedIn this ocperiment you will allow sodium bicar'

bolate (baking soda) to renct with hydrochloricacid for the purpose of obtaining a high yield of

sodium chloride.

NaHCOs + HCI -+ NaCI+HgO*CO1G)Eq.'t'

lbu will use an acctrratel;- meastrred mass of

NaHCOs and enough dilute HCI to completelyreact with it. l'ou will rsglate thc NaCl from the

othir producs and deterrnini is masl. Thetheoretical )'ield can be calculated by using 3hbmole and mass ratios obtained from the balanced

equadon for the reaction. The percenqge yield

can then be determined by comparing the experi'

mental vield with the theorctical vield..

OBJECTIVESl. To prepare and determine the yield of

sodium chloride.3. To gain. an understanding of mass relation'

ships in chemical reactioru.

MATERIALSEvaporating dish. rvatch glass. balance. sodium

bicarbonate (CP), hvdrochloric acid. burner, wirc

gauze, ring stand, r,t'ash bottle.

PROCEDUREl. Clean and dl-v an evaDorating dish and

rratch'gl'ss. and weigh the combination to thenearest 0.01 g. Record the data in the table.'

mass of cvaporating dlsh.cc,rcr, and NaHCOs

i Trial t-- i-| ;: rt . l

mass of esaporating dishand rrarch glass

mass of NaHCOa token i {mass of evaporating dish,colgr. and NaCl

I

I

mas of cr'rporating dish andcover litem 2 above)

rnass of salt obtained(expcrimental)

theorctical mass of salt(calcu}ated) Rpercentage yield f

2. Rrt about 2 g of pure sodium bicarbonateinto the dish. Weigh the dish. contenrs, and coverto the neaF*t 0.01 g.

3. Cover the dish with the watch glass. Placethe conrrcx side down and the glass slightly offcenter so that the lip of the dish is uncovered. Adddilute hvdrochloric acid dropwise down the lipof the di$ io the bicarbonate-in the dish. C.on-tinue thifindiedure until no more i;eetion takesplace when a drop of acid is added. Gentiy svvirlthe conrcnts of the dish so that all of the solidcontacs the liquid. Do not add excess hydrochlqric acid.

4. Carefull,'- rirue the underncath side of thewatch glass with distilled warcr, a ferr drops at atime. and collect the washings in the dish.

5. Heat the evaporating dish, contenu andcover with a low flame until the salt is completclydry. If the contents of the dish pop and spirtter,rduce the ftame.

Sz

ilt ffiffi*-.r,,dfff;flgm:nffi*"i.* "*ff*.fl**'

R RTHER u.follglofr obtaining purc i#(roo) = e3'{c'c

Devisc anothcr dFrimcnt tc rtz s l^eot ..Nacr' *FolLowup QuEsnors v: Z^ *Y

FoLLowuP DlscussloN l' wh't *L ttt" o"* of thc cicrntsccncc

Thc rcaction whicrr yor uscd t t*T il *'ia' y"" t*J* tt indication of the progrcss of

*r. u .irr" ",+"rlt"*,

.l*P--l-* Procccdcd ro * **o% rcasons wh-v the rcactim in rhi:

ilil;.-flb rypc of rcaaion i" "ltt y": 2' Givc

orcoarc wcaHy dissociatcd tcr;-It -"y uc t""o ;d; shorld have gone to comPteuotr'

[I#"o"-ril, e, *,y*#itffi, ffi#"S ffi ,:t*Sff;''.Hf;aija

"na tft" :alt of a wear aoo"

,Y,l*j:::; TtT" :!c rsrs 'ru -- -- -

ii l'*r.ri." it . "v1*

acid: we can assl; dcrivcd

ihat when a *!ong acrd rc"rtsr to form a *cah *n.

iil* a" y"n, bc sure that your prodrrt wer

l5i ,it- - t-" oli" tT5 acid arc rcrnovco

addcd exccss hvdrochbric rcaili

--r"tr.". Hcace' thc rcaction procceos rt' lt vo

cscntiall-v to complction'.uffi Hlt* tJH"#tff;-t*"t" t"{ dti,T-Tt"d

weak acid formed as a Proouq was carbonic e'cid' *"lf"ti*t]'i'"" *o"U havc detecrcd-enirritet'

S::a,1ffi nff*'g*m fffi ; ;tihinrr i'ls namc and ro'mura

'J;;;;P"";d *: *:#;l;fgl X*tfm""i**"ffi m,,'ritrcn in irs- dccomnocco..lo,1"r.tdt" -r"d

a poor ; ffi ;;T;-ii. -J".io"

containcd prre.{ solution of carbonic scrd ts acr:ri:-:;^L.l*., ' l9u-.:-

tryirTJe{,FtT#t-'..'fi $}.*:ii-":'*r[.:'":ffi t";;ffi ;T#:C0rt ion ard CO2. sest a rcE-6,,. oivo,,".o j*uTi-::i ::fHHH 4:;;LT':i"f;; X3:*?"... thich roul:df :;thi:: iffliiH;; ;;-pr: i'. pY,r,"r?.r''L* i'i"'"""a thc acc'rae or Yo.r'idcd to assist vou "t

,,'t*"ii*trtl"i"at"a'""r- llp""-";tlii;r* \Atc:ct'er t*tjlt:ttt-'

"FllT;-*,*.r vicrd is'*^';';o-"' l$t:;#'*-"':"':'.:l:::NaHCos+H., ; n"",1t,"+co:(s) "":mt*lfHffr?llTlT:ffi IFrom the balanced eguation. it nlav be scen tiors for each Part'

rhat r mole "rltl;;C'il P'od::::-t;Hi:":j 3Ae(s) + ,tHNos

$:t,lJ::."lylr??"*Tii':Hc6;,:; 3As(s). *"1?'J,its;+ No1s1 + zHg( I

rrsed. ,., i.oo $a; of NaHco3 rvcre '';:;N6r(aq)

+ No1g1 + ZHro(l) i'tI

5E

StoichiometryPost-LabDiscussionandWrite-up * Do {tb:8 orn fte ba.K.

l. Write the balanced chemical reacJion for tle ei<periment perforned:

---->

. 2. On tbe back ofthis paper draw a diagram of the equipment and apparatus used in the e4erimefr. Be

. sur€ to label all of tbe coqoneds.

3. Remember, Gross Mass - Tare Mass = Net Massa. What is your Tare Mass (empty evap dish and watch glass)?b. You were to start with approximately 2gofNaFICO: but the actual amount can ,

be detennined by:

Gross Mass (Evap Distu Watch Glass and Baking Soda):Tare Mass (Empty Evap Dish and Watch Glass):Net Mass (Baking Soda Only aka NaHCOT):

4. Now we want to take the gram.s ofNaHCOl (substance A) and convert it into grafiis of NaCl(substance B) using orrr 3 step conversion process.

Step 1: Convert g NaFICOg into moles ofNatICO3

Step 2: Convert mol NaHCOI into mol NaCl

Step 3: Convert mol NaCl into g NaCt. This will be your theoretical amount ofNaCl.

5. Now we need to determine the experimental (actual) amourt ofNaCl produced.

Gross Mass (Mass after heatin,g or use constant mass):Tare Mass (Eryty Evap Dish and Watch Glass):Net Mass (NaCl Only, This is the actual amourt):

6. Determine the percent yield ofNaCl produced in the experimerfi:

VoYield: Actual x 100Theoretical

yg"lc,rw.ine fl.c perceot ortar. o/oetrr = $ffip'*,oo7. Most likely your perce* yield was not l0@/o urhich is due to errors in your experinnental tecbnique.Explain tfiree differeut errors that occurred 61 might have occurred during yorn experinent and bowtlrey could have affected yow results. This is a thinkmg question, be as detailed as possible!

8, U,hioh v<actant in fiv lat waa linitiry ?. b'+*t^ ov* wat Mexqsg'l. Urtl d- yo,^ txuf if is iv,,p-i,,-t to ho,e ov.v- leattalrrfVe i rn ex@sS ?