Percentage-Purity-Percentage-Yield-Worksheet-Solutions-ypyqig.pdf

This ppt explains the calculation of percentage of purity of compounds. SUitable for IGCSE and A level chemistry students

1. CHEMISTRY 11 AP – PERCENTAGE PURITY & PERCENTAGE YIELD WORKSHEET

1) A saturated solution of lithium fluoride, which is sometimes used as a rinse to prevent tooth decay,
contains 0.132 g of LiF in 100.0 g of water. Calculate the percentage purity by mass of the LiF.





2) Automotive air bags inflate when solid sodium azide (NaN3) decomposes explosively into its
constituent elements. What volume of nitrogen gas is formed if 120 g of 85% pure sodium azide
decomposes? Assume STP conditions.










3) What volume of chlorine gas could be produced under STP conditions if 39.8 g of 84.0% pure
potassium chloride were reacted with an excess of fluorine gas?










4) The thermite reaction is extremely exothermic, producing temperatures in excess of 2500°C. These
high temperatures were used to weld iron tracks together during the early days of the railway.
Thermite is a mixture of powdered aluminum and iron (III) oxide (rust) reacting as follows:

2 Al (s) + Fe2O3 (s) → Al2O3 (s) + 2 Fe (s)

If 2.44 g of 95% pure aluminum is reacted, how many grams of aluminum oxide can be produced?









%purity
=
0.132g
100.0g
×100%
=
0.132%
2NaN3→2Na+3N2
gpure
NAN }
=
85%of
120g
=
0.85×1209=1.0×1029
LNa=1.0×103
NaN3×
dsmowaaghbxgemmondvanisx ,2m2oYn's
=
52L
QKCI+Fa
→2KF
+Cbn
gpure
KCI
=
84.0%of39.8g
=
0.840×39
.
8g
=
33.4g
LCK
=
33.4g
Kdxlmdkcl
22.4LIMOICK
X
|mo1d274.559×2molkcl
=
5.02L
gpure
At
=
95%of2.449=0.95×2
.
44g
=
2.3g
g
Ala03
=
2.
3g×
lmdAt IMOIAKQ
×
101.96g
26.989×2MOIAI IMOIAHG
=
4.4g

2. 5) A 25.0 g sample of calcium oxide is heated with excess hydrochloric acid to produce water and 37.5
g of calcium chloride. What is the percent yield of the reaction?














6) A solution containing 15.2 g of barium bromide is reacted with a solution containing excess sodium
phosphate to form 9.5 g of barium phosphate. What is the percentage yield of the reaction?














7) Copper (II) oxide reacts with hydrogen gas to form water and copper metal. From this reaction, 3.6
g of copper metal was obtained with a yield of 32.5%. What mass of copper (II) oxide was reacted
with the excess hydrogen gas?















CAO +2ha
→ H2O+ Cack
gcacla
=
25.OgCaO×
IMOICAO 110.98g
jmdcackx
|mo|Cad256.089×/mdca0
=
49.5g(theoreticalyield
if100%completion)
%yield
=
3759
×100%
=
75.8%
49.5g
3BaBr2t2Na3P04→6NaBr
+BadPODA
gBaz(PO$a=15.2g
Babrax
lMdBaBr2 /molBa}DOy)2601.93g
297.13g×3mdBaBr2
×
IMOIBAKPOYK
=
10.39(theoreticalyield
if100%completion)
%yield
=
9.5g
10.3g
×100%
=
93%
CUO
+Ha
→ Haotcu
gCuO=
3.
bgcux
IMOICU IMOIAO
×
79.55g
63.559×1molcu IMOIAO
=
4.59(theoretical Cuousedif100%completion)
32.5%
=
45×9
x100%
×
=
14g
(14gofCUO was
thestarting
mass
however
Only
4.Sgofthecuo
actually
underwent
a
reaction)

3. 8) A 20.0 g piece of calcium metal reacts with 18.0 mL of water over time. If 10.0 L of hydrogen gas
is formed under STP conditions, what is the percentage yield of the reaction? Recall the density of
water is 1.00 g/mL.















9) A sample of impure silver with a mass of 0.7294 g was dissolved in excess concentrated nitric acid
according to the following unbalanced equation:

Ag (s) + HNO3 (aq) → AgNO3 (aq) + NO (g) + H2O (l)

Once the nitrogen monoxide gas was vented off in a fume hood, the resulting silver nitrate was
reacted with a slight excess of hydrochloric acid to form a precipitate of silver chloride. The dried
precipitate was 0.3295 g. What was the percentage purity of the silver sample?
Cat 2h20→ HatCAIOHK
Latta⇒
oogeaxtymooosagximmoictakx
92mm
.a=
'''
ftp.pis.omutaoxlfomqtboxlg?0oY50xdmmoYtY5ox2m2oYIa=n.aL
bothreactantsproduce
the same
amountof11.2LHa
i.bothreactants
are
used
up
completely
%yield
=
49.029×10040=89.4
%
balance first
3 4 3 2
-
^
-
Agnostics
Agat
HNB
eideabehindthisquestion
istofinda common
cthhemicalspecies
between
the2reactions
.
Thatchemical
isAgnos
.
gAg=
0.3295g
Agdxlmdttsd
lmdA9NB×3md
As
×
1,0mg,87agg
143.329×1
MOIAGCI 3m0lAgN03
.
=
0.2480g 2stoichiometrysteps
%purity
=
0.2480g
rewired
tolink2 reactions
0.7294g
''100%
=
34.00%