Determination of the Thermodynamic Parameters for the Solvation of Borax

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Kaley Goatcher

9 April 2012

Chem 122L


02



1


Determination of the Thermodynamic Parameters for the Solvation of Borax




In an effort to learn about

the
principles of thermodynamics
,
saturated Borax
solution was titrated with HCl

in the laboratory.

K
sp

for T
1

and T
2
were calculated to
be 6.23x10
3
and 5.50x10
2
, respectively.


Introduction


Thermodynamics is the science concerned with heat and the mechanical energy of work. In this
lab, three thermodynamic principles will be studied: Std. Gibbs Free Energy Change, Std.
Enthalpy change, and Stan
dard Entropy Change. By measuring the equilibrium constant for our
solvation reaction, we will be able to determine the Standard Gibb’s Free Energy Change for the
reaction. This can then be related to the standard change in the Enthalpy and Entropy for t
he
experiment’s chemical reaction. The Borax we will use is commonly found in dry lake beds.
It’s used in soap, preservatives, glass manufacturing, and cleaning products.
T
his
is a
presentation

of
our results for the

Determination of the Thermodynamic P
arameters for the
Solvation of Borax

l
aboratory
e
xperiment
.





Experimental Data

The
procedure

was

completed as follows:

Preparation of
Saturated Borax Solution



Combined Borax, water, and stir rods in two separate Erlenmeyer flasks
.



Allowed one flask
to stir at room temperature for 30 minutes.



Allowed the other flask to stir in an ice bath for 30 minutes.



Allowed solutions to sit until start of titrations.

Preparation and Standardization of HCl Solution



Combined HCl and water in beaker in fume hood.



We
ighed out anhydrous Sodium Carbonate and added it to Erlenmeyer flask.



Added 50mL of water and dissolved.



Added indicator.



Titrated solution to the endpoint.



Repeated for all 3 solutions.



Calculated HCl concentration.

Determination of the Borate
Concentration



Recorded temperature of saturated Borax solution.



Decanted solution into dry beaker. Added a few drops of indicator.



Titrated solution to the endpoint.

Kaley Goatcher

9 April 2012

Chem 122L


02



2




Repeated titration twice more.



Repeated procedure with the second saturated Borax solutio
n.



T
he results are:


HCl Standardization


Ice Bath


Room
Temperature

Trial #

mL


Trial #

mL


Trial #

mL

1

25.3


1

14.7


1

25.6

2

25.2


2

14.5


2

25.8

3

25.4


3

14.5


3

26.1

Average

25.3


Average

14.57


Average

25.83



D
ata Analysis


1.

Molarity of T1= 14.57
mL Borate/(192g Borate/mol

Borate x 0.0119L borate) = 6.38

M


Molarity of T2= 25.83
mL Borate/(192g Borate/mol

Borate x 0.0119L borate) = 11.31

M


2.

[Na+](T1)= 2 x [6.38] = 12.76

M


Ksp(T1)= [11.31]^2 x [6.38] = 8.16
x10^2


[Na+](T2)= 2
x [11.31M] = 22.62


Ksp(T2)= [22.6M]^2 x [11.31M] = 5.78
x10^3


3.

Δ
G(T1)=
-
(8.314)x(273K)x(ln(
8.16x10^2
))=
-
1.52
x10^4


Δ
G(T2)=

-
(8.314)x(298K)x(ln(
5.78x10^3))=
-
2.15
x10^4


4.

Δ
H=
-
[(8.314)xln(
5.78x10^3
/
8.16x10^2)/(1/298K


1/273K)]= 5.30x10^4


5.

Δ
S(T1)=
(
-
1.52x10^
4


5.30x10^4
)/
-
273K =
-
76.4



Δ
S(T2)=
-
2.15x10^4


5.30x10^4
)/
-
298K =
-
94.5



Kaley Goatcher

9 April 2012

Chem 122L


02



3


6.



C
onclusion

Possible sources of error most likely occurred in
the
mixing of chemicals.
If the chemicals were
not mixed properly

and if the
Borax

was not measured out

with a significant amount of accuracy,
the solutions would turn out poorly and the experiments would not go as planned.
In the future,
we

will do more to
ensure
our

measurements and solutions are correct before proceeding with
the
titrations
.

After completion of the lab,
we

w
ere

able to see how
the principles of
thermodynamics affect chemical experiments
.
Overall, given the
laboratory conditions, this
expe
riment effectively demonstrated how to
analyze the
pri
nciples behind
Thermochemistry
.







Post Lab Questions

1.

This reaction is endothermic. It is enthapically favourable. Yes, we expected this reaction
to be endothermic.

2.

Yes, the lab is entropically
favourable. This did not agree with our expectations. The
molecules had to bread the hydration layers.

3.

Pink molecules; tetrahedral

4.

Entropy increases because more gas molecules are being produced.

5.

Δ
G is Gibbs Free Energy at constant T.
Δ
G
°

is Standard Gibbs

Free Energy calculated
using standard conditions standard temperature and pressure.

Data Analysis

See attached.


Ksp

Δ
d

Δ
e

Δ
p



㔮㜸5㄰13

-
㈮ㄵ2㄰14

㔮㌰5㄰14

-
㤴⸵



㠮ㄶ8㄰12

E
-
ㄮ㔲1㄰14

㔮㌰5㄰14

-
㜶⸴