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Lecture 7

CHEM 1LC Lecture Notes - Lecture 7: Flame Test, Nitric Acid, Nichrome


Department
Chemistry
Course Code
CHEM 1LC
Professor
Mc Millian
Lecture
7

This preview shows pages 1-3. to view the full 15 pages of the document.
LAB$07$ THE$SELECTIVE$CRYSTALLIZATION$OF$KNO3$&$NaCl$NOTES$
GENERAL$CHEMISTRY$
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Commercial$production$of$various$salts$
from$many$source$depend$on$what$
principles?$In$turn$which$depend$on?$
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What$does$a$saturated$solution$of$a$salt$
involve?$
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In$solution,$what$is$occurring$at$
equilibrium?$$
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The$salts$that$will$be$used$supply$with$4$
kinds$of$ions?$
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From$the$mixture$of$ions,$it$is$possible$to$
form$what$4$crystals$salts?$
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Salt$crystallization$first$depends$upon$
what?$$
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When$we$increase$the$concentration$of$
either$both$the$ions$involved$in$a$particular$
reaction$it$will$increase$the$chances$of$what$
to$occur?$
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FUNDAMENTAL*CONCEPTS*
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$The$commercial$production$of$various$salts$from$
many$sources$depend$on$the$principles$of$!"#"$%&'"()*+(
,+-$%&*.-#/($+0!%-##&1-%&*.,$which$in$turn$depends$on$
the$principles$of$solubility$equilibria$of$the$salt$
mixtures,$and$on$the$effects$of$temperature$and$of$
concentration$of$these$equilibria.$$
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SATURATED*SOLUTIONS*
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$A$saturated$solution$of$a$salt$involves$an$equilibrium$
between$the$rate$at$which$molecules$or$ions$are$
depositing$on$the$surface$of$the$solid$crystals$and$the$
rate$at$which$molecules$or$ions$are$leaving$the$crystal$
surface$and$mixing$with$the$solvent$molecules$in$
solution.$$
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- @$equilibrium$the$opposing$rates$are$
equal,$so$that$the$concentration$of$the$
solution$remains$constant$at$any$given$
temperature.$$
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$The$salts$that$will$be$used$supply$4$kinds$of$ions:$$
Na+$
K+$
Cl-$
NO3-$
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- From$the$mixture$it$is$possible$to$form$any$
of$the$4$crystalline$salts$
o NaCl$(s)$
o KCl$(s)$
o NaNO3$(s)$
o KNO3$(s)$
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- Which$particular$salt$crystallizes$first$will$
depend$upon$the$temperature$and$the$
relative$concentrations$of$the$several$ions$
in$solution.$$
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- Increasing$the$concentration$of$either$(or$
both)$of$the$ions$involved$in$a$particular$
reaction$would$increase$the$chances$of$

Only pages 1-3 are available for preview. Some parts have been intentionally blurred.

LAB$07$ THE$SELECTIVE$CRYSTALLIZATION$OF$KNO3$&$NaCl$NOTES$
GENERAL$CHEMISTRY$
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interaction,$and$thereby$increase$the$
chances$of$interaction,$and$thereby$
increase$the$probability$of$precipitation$of$
the$corresponding$salt.$$
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THE*THEORY*OF*SELECTIVE*CRYSTALLIZATION*
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$The$solubility$of$A$increases$rapidly$with$increasing$
temperature,$while$that$of$B$increases$only$slightly.$$
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$In$area$1$–$below$both$curves,$the$solution$is$
unsaturated$with$respect$to$both$A$and$B.$$
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$In$area$2$–$it$is$unsaturated$with$respect$to$A,$
saturated$with$respect$to$B,$and$contains$excess$solid$
B.$$
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Only pages 1-3 are available for preview. Some parts have been intentionally blurred.

LAB$07$ THE$SELECTIVE$CRYSTALLIZATION$OF$KNO3$&$NaCl$NOTES$
GENERAL$CHEMISTRY$
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Calculate$the$mass$of$¾$moles$of$each$of$
crude$NaNO3$and$KCl.$$
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Why$do$you$want$to$filter$the$mixture$
when$hot?$
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EXPERIMENTAL*PROCEDURE:*
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$Will$prepare$potassium$nitrate$by$selective$
crystallization$from$crude$Chile$saltpeter,$NaNO3$and$
crude$potassium$chloride,$KCl.$$
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- Sodium$chloride$will$also$be$obtained$as$a$
byproduct.$$
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PREPARATION*OF*POTASSIUM*NITRATE*AND*
SODIUM*CHLORIDE*
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Calculate$the$mass$of$¾$mole$each$of$crude$NaNO3$
and$KCl.$$
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Molar$masses:$
NaNO3$=$84.99$g/mol$
KCl$=$74.55$g/mol$
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¾$mole$of$each$$
NaNO3$=$63.68$g$
KCl$=$55.91$g$
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$Place$weights$of$NaNO3$and$KCl,$together$with$
water,$in$beaker,$and$heat$the$mixture$almost$to$
boiling$in$order$to$dissolve$salts.$$
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$Filter$while$hot$with$the$aid$of$vacuum,$to$remove$
any$insoluble$foreign$matter.$$
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