Chem 1711
Ch 4: sample problems based on reactions in aqueous solution
1.
Determine the volume (in mL) of 1.098 M KOH (aq) required to completely neutralize 80.0 mL of 0.685 M H2SO4 (aq).
2.
Determine the theoretical yield (in g) of precipitate that can form from the complete reaction of 75.08 mL of 0.249 M Al(NO3)3 (aq)
with excess Ba(OH)2 (aq).
3.
In a titration experiment, 20.00 mL of 0.9876 M Sr(OH)2 (aq) is titrated with HNO3 (aq); 31.15 mL of the nitric acid solution is
required to reach the stoichiometric point. Determine the molar concentration of the acid.
4.
A small amount of CoC2O4 is dissolved in a warmed, acidic solution, and titrated with KMnO4 (aq). The net ionic equation for the
reaction that occurs is given below:
5 C2O42 (aq) + 2 MnO4 (aq) + 16 H+ (aq)  2 Mn2+ (aq) + 10 CO2 (g) + 8 H2O (l)
Determine the mass (in g) of CoC2O4 used in this experiment if 18.42 mL of 0.0206 M KMnO4 (aq) is required for complete reaction.
−
5.
Saccharin, C7H5NO3S, is sometimes dispensed in tablet form. Ten of these saccharin-containing tablets have a total mass of 0.5894 g.
These ten tablets were dissolved in water, and then oxidized so that all the sulfur present is converted to sulfate ion. Next, excess
BaCl2 (aq) was added so that the sulfate ion was removed from solution as BaSO4 (s). The mass of barium sulfate collected was
0.5032 g.
a. Determine the average mass of saccharin per tablet.
b.
6.
7.
−
Determine the average mass% saccharin in these tablets.
A mixture contains only NaCl and Fe(NO3)3. A 0.456 g sample of the mixture is dissolved in water, and then an excess of NaOH is
added, resulting in the formation of a precipitate of Fe(OH)3. The precipitate is collected by filtration, and dried; the mass of Fe(OH)3
collected is determined to be 0.107 g.
a. Determine the mass of iron in the original sample.
b.
Determine the mass of Fe(NO3)3 in the original sample.
c.
Determine the mass percent Fe(NO3)3 in the original sample.
A pesticide sample is analyzed to determine its thallium content. In this pesticide, thallium is present as Tl2SO4. A 9.486 g sample of
the pesticide is prepared, and the thallium present is precipitated out in the form of thallium (I) iodide. Calculate the mass percent
Tl2SO4 in the pesticide sample if 0.1824 g TlI was recovered.
Ch 4: sample problems based on reactions in aqueoussolution
Chem17ll
FlrJorr f
l.
I Korf --9
(2S0? * aHzo
Determinethe volume (in mL) of 1.098M KOH (aq) requiredto completelyneutralize80.0 mL of 0.685 M H.SO. (aq)
. 0 t r 0 0f s o l r n 2 g' L 8 ' S n ^t /o. l5 0,t ? ^ " ? - l ^ ' L ' d ' ^
t Lsol i
I mrl Fl150y
-
??-8 r,,rL KoH fe1)
= . o1?8 L rA
t. o19,"nor 14r.1
Determinethe theoreticalyield (in g) of precipitateth4t ca4 form from the completereactionof 75.08 mL of 0.219 M AI(NO.). (aq)
wirhexcessBa(oH),(aq).
ZAif"orl(r11 |3tsatoU)rrt) -+ ZAl1ou\k) -(-3OaCuor)2tj)
18 ' Oo3 - :
4ro.ro:):,"2qol 4lfotJ)g
, O-lsogLsorh, .zv?r,'rol
t,4L3Al(aA)3
r
'
'2.!b$l4l tvo3)3
I Lsolh
I nao{AI G+i,
In a titrationexperiment,
20.00mL of 0.9876M Sr(OH),(aq)is titratedrvithHNO.r(aq);3l .15mL of thenitricacidsolutionir
requiredtoreacithestoichiometricpoint.DeterminethemolarconcentrationoruLu"iH
a .Ns o
r (3o($r 1
[ +) .- f+ 5 r ( r { O ) t
rnul trNo3a|. s*oict..pf . = .02000!sorxx ,18-]6naot
sr(oll)r^
...FrnoJ=4*ffi^=
A
,-._[t^"Norr;)
t
.?-*ifrrvvrol
,trl",,g=0,
5rtoil2
+2H20
,0395 0nnolHM$
j'
>
.o3llsLs
A small amountof CoC"O.,is dissolvedin a warmed,acidic solution,and titratedwith KMnOr (aq). The net ionic equationfor the
reactionthat occursis given below:
5 CrO*' -(aq)+ 2 MnO.: (aq) + I 6 H* (aq) - 2 Mn2*(aq) + I 0 CO, (g) + 8 HrO (l)
Determinethe mass(in g) of CoC.O.,usedin this experimenlif 18.42mL of 0.0206M KMnO, (aq) is requiredfor completereaction.
,Uf,rzlsot,rr;.0zoL,hpilo,rho4^,^.,Tlol
*S*'l_A0t.*ll"',?!.3 * _'qfjJ, = ,l3?3 GC2o,
|Lsol.^|nc|[rr4D1ZmolMa01|*ro|C1o{-.-1rr'roltoC20.1*
-5.
is sometimesdispensedin tabletform. Ten of thesesaccharin-containing
Saccharin,C7H.5NO.S,
tabletshave a total massof 0.5894g.
Theseten tabletsrveredissolvedin rvater,and then oxidizedso that all the sulfur presentis convertedto sulfateion. Next, excess
BaCl, (aq) r.vasaddedso that the sulfateion r'vasremovedfrom solutionas BaSO, (s). The massof barium sulfatecollectedrvas
0.50329. arts in fu^blds:+
a.
b.
to,i]; 9lr<n ga2+c1rj- sOf ("d--+
Determinethe averagemassof saccharinper tablet.
Bas'*^
.50323
ffi{#;
gasoq ts)
No35
='i.lffv,^qT;
hlld3
,
#*".#ffi
secc/ta'rirr a"\^t^3L
".0' o3950
------- 3
L)eterminethe averasemass7osaccharinin thesetablets.
p.^ JilJ+
.d395DJsqcc. I to6=n.0&
-Dsg?lJ)ztt<+
cZHsMJx
or qsLArl{+1rrl.
rn4ssZ s^cc.= ' 3q9-,
- 166= L?.02?. sacc.i
,5.^ftAfct
,581q c +abkt
b* t''.'e.L6
--:.
J
A mixture containsonly NaCl and Fe(NO.).. A 0.456 g sampleof the mixture is dissolvedin rvater,and then an excessof NaOH is
added,resultingin the formation of a precipitateof Fe(OH).. The precipitateis collectedby filtration, and dried; the massof Fe(OH).
collectedis determinedto be 0.107 g.
a. Determinethe massof iron in the original sample.
lR.Sf"Xl
3 os- (aX)-> fu to#)3 ( s)
, I 0-b p (oH! x t"n)| R,(gl):
I nno/F<-. * s S .f i s j : . o 5 S ? r F e
"
Iob.1J
-+lyqol R.tofi], l r n o l f u
b.
Determinethe massof Fe(NO.). in the original sample.
, D55?J k
c.
,r"o
t Fe*
'
x Iss.T!'
I'nor lA (rug)g
l,r^ol fl-
e + l, 1 J
,Q1E ritrug)3
-"-=-=--
f rror R fN%\
Determinethe masspercentFe(NO.,).,
in the original sample.
R-rrvor),
x I DO:
ruass
= ,iYa-1
z R.crvor),
Janplt,|-tSbJ
)t
5 3. 17 Fe 6"'lo-t
-___J
bq wrol'n
A pesticidesampleis analyzedto determineits thallium content. In this pesticide,thallium is presentas TI'SO*. A 9.486 g sampleof
the pesticideis prepared,and the thallium presentis precipitatedout in the form of thallium (l) iodide. Calculatethe masspercent
TI,SO, in the pesticidesampleif 0.1824g Tll was recovered.
Tlr lsl
T.t**(^b,+ T-fd
l,*"13]^ l:o'J{t$u^ sCr'-l.13 = , 1 3 1 j l & r o t
.rBz.fjT-Q.1x
)+IJ+rn
3 3 1. L J
t\^q.AA% T:Qrsot :
lvr.rulTlL
{Yrtof I{
1 3 9 3T:QrJoq
1 .1181.6 v*pl <
lntr(T.{2S0,
oo:
t . + 1 % T r r s o+ b 8
h^455