Uncertainty in weighing scale (∆M) = ± 0.01 g
Mass of Zinc taken (m) = 2g
Uncertainty in mass of zinc (∆m) = ± 0.01 g
Specific Heat capacity of CuSO4 (c) = 4.184 J/g°C
Data Processing
Graph of temperature Vs time when zinc powder was added to Copper Sulfate
Intitial temperature (t1) = 27 °C
Final temperature (t2) = 65 °C
Change in temperature (∆T) = (65-27) °C => 38°C
Uncertainty in change of temperature = 0.2 + 0.2 => ±0.4°C
Total Heat absorbed by CuSO4 (Q) = m×c×∆T
= 25×4.184×38
= 3974.8 Joules
= 3.974 kJ
Uncertainty in Q (∆Q) =
= ± 0.116% ≈ ±0.0046 kJ
Molar enthalpy of reaction (∆H) = Q/n
n = concentration of solution(c) × Volume of solution(v)
= 0.1×25/1000
= 0.025 moles
∆H =
Uncertainty in ∆H = 0.116% ≈ ±0.184
Conclusion and Evaluation
The value of the molar enthalpy of the reaction of copper sulfate and Zinc was found out to be (158.99 ±0.184)
Some of the heat loss was accounted for by extrapolation of the graph however the theoretical value is 217
Percentage Deviation from Literature value =
≈ 26.73%
This deviation is due to a number of system and random errors.
System errors:
The calorimeter was made of copper. Copper is a good conductor of heat and it also might have got displaced by zinc in the reaction.
The calorimeter had insulation against heat loss due conduction but not against convection and radiation. The insulating material would be efficient only to stop conduction.
The stirrer was also made of Copper which might have reacted with zinc and the copper sulfate solution.
The zinc was not finely powdered which might have led to an incorrect reading.
Random Errors:
Only one reading was taken.
While transferring zing from the watch glass to the calorimeter some of it was stuck to the glass.
While pouring copper sulfate from the measuring cylinder to the calorimeter some of it was stuck to it.
The initial temperature of copper sulfate was taken in the measuring cylinder and not the calorimeter. Some heat exchange might have taken between the two.
There was a parallax error while taking the reading of the measuring cylinder.
Error Correction
A pipette should have been used instead of the measuring cylinder as this would ensure less sticking of copper sulfate to the vessel and greater accuracy.
A Styrofoam or a glass calorimeter should have been used which would not react with the solution or zinc.
The inside of the calorimeter should have been coating with a reflecting paint as this would reduce heat loss by radiation.
More readings should have been taken to reduce random error.
The initial temperature of copper sulfate should have been taken when it was in the calorimeter.
A plastic stirrer should have been used as it would not react or conduct the heat leading to any heat loss.