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Determining enthalpy of reaction for Zn(s) + CuSO4(aq) -------> Cu(s) +
ZnSO4(aq)
Raw Data
Substances
Mass (+/- 0.005g)
Initial Temperature Final Temperature
(+/- 0.05 Celsius) (+/- 0.05 Celsius)
Volume (+/- 0.5 mL)
22.1
25
Cylinder without Zn 31.32
Cylinder with Zn
31.81
0.5mol/dm3 CuSo4
49.2
Explanations of Uncertainties:
Least count of the instruments used for measurement divided by two.
Mass was measured by electronic balance and the least count of the instrument was 0.01 g. The least
count is divided by two to obtain an uncertainty of +/- 0.005 g.
Temperature was measured by a SPARK Data Logger and the least count of the instrument was 0.1
Celsius. The least count is divided by two to obtain an uncertainty of +/- 0.05 Celsius.
Volume was measured by a 25 mL graduated cylinder and the least count of the instrument was 1 mL.
The least count is divided by two to obtain an uncertainty of +/- 0.5 mL.
Qualitative Data: Before
Zn(s) was in small, spherical granules, and grey in color.
CuSO4(aq) was a teal blue color, viscosity somewhat thicker than water, and transparent.
Qualitative Data: After
Afterwards, the solution was dark blue and grimy. It remained transparent, and its viscosity did not
change.
Processed Data: Substances
Mass (+/- 0.01 g)
Zn
0.49
Temperature Difference
(+/- 0.1 Celsius)
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ZnSO4
27.1
Explanation of Uncertainties: When adding or subtracting, the uncertainties of the two raw measurements are added.
Mass of Cylinder with Zn was 31.81 +/- 0.005 g subtracted by Mass of cylinder without Zn 31.32 +/0.005 g equals to 0.49 +/- 0.01 g.
Temperature Difference was obtained using the final high temperature 49.2 +/- 0.05 degrees Celsius
subtracted by the initial temperature 22.1 +/- 0.05 degrees Celsius obtaining a value of 12.5 +/- 0.1
degrees Celsius.
Calculations:
qlost = -qgained
q= -mc^t
q= -(25g +/- 0.5)(4.18)(49.2-22.1)
q= -(25g +/- 0.5)(4.18)(27.1 +/- 0.01)
q= -(25g +/- 0.5) (4.18)(27.1 +/- 0.369%)
q= -2831.95 +/- 2.369%
q= -2831.95 +/- 1 J / 1000
q= -2.83195 +/- 2.369% kJ
*specific heat assumed to be the same as water
*density of solution assumed to be the same as water
n= mass of zn /molar mass
n = (0.49g +/- 0.01) / 65.38
n = 0.00749 +/- 2.0408%
Formula for delta H: q/n
H= -2.83195 +/- 2.369% / 0.00749 +/- 2.0408%
H= -378.097 +/- 4.4098% kJ/mol
H= -378.097 +/- 16.673 kJ/mol
Delta H = -378 +/- 17 kJ/mol
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