Calculating the Enthalpy Change of Reaction for the Displacement Reaction Between Zinc and Aqueous Copper Sulphate
Calculating the Enthalpy Change of Reaction for the Displacement Reaction between Zinc and Aqueous Copper Sulphate
Data Collection and Processing
Observations: * Drops of water left on the inside of the measuring cylinder * Hole in the lid, possible escape route for gas or splash-back * The polystyrene cup felt warm during the reaction
By extrapolating the graph we can estimate what the rise in temperature would have been if the reaction had taken place instantaneously. I can conclude that if the reaction had taken place instantaneously, the solution would have reached a temperature of 450C. * Calculate mass of the copper sulphate solution: mass = volume x density = 25 x 1 = 25 g * Calculate change in temperature when the zinc is added:
ΔT = Tmaximum - Tminimum = 45 – 20 = 25 0C * Calculate the number moles of copper sulphate reacted: number of moles = concentration x volume = 0.5 x 0.025 = 0.0125 mol * Calculate energy released during the reaction (Q):
Q = mass of CuSO4 x specific heat capacity x ΔT = 25 x 4.2 x 25 = 2625 J * Calculate ΔH for the reaction (energy change is negative because the reaction was exothermic):
ΔH = -Q / number of moles = 2625 / 0.0125 = 210 kJmol-1
‘Absolute Uncertainty’ = abs/unc
‘Percentage Uncertainty’ = %unc
Uncertainty in mass = (%unc in density + %unc in volume) x mass
= (0 + 0.5/25) x 25 = ±0.5 g
Uncertainty in temperature change = abs/unc in Tmaximum + abs/unc in Tminimum
= 0.5 + 0.5 = ±1 oC
Uncertainty in number of moles = (%unc in concentration + %unc in volume) x number of moles
= (0 + 0.5/25) x 0.0125 = 0.00025 = ±0.0003 mol
Uncertainty in energy change = (%unc in mass + %unc in temperature change) x energy change
= (0.5/25 + 1/25) x 2625 = 157.5 = ±200 J
Uncertainty in ΔH = (%unc in energy change + %unc in number of moles) x ΔH
= (157.5/2625 + 0.00025/0.0125) x 210 = 16.8 = ±20 kJ/mol
Final Value of ΔH: -210 ± 20 kJmol-1
Conclusion
The accepted
Data Collection and Processing
Observations: * Drops of water left on the inside of the measuring cylinder * Hole in the lid, possible escape route for gas or splash-back * The polystyrene cup felt warm during the reaction
By extrapolating the graph we can estimate what the rise in temperature would have been if the reaction had taken place instantaneously. I can conclude that if the reaction had taken place instantaneously, the solution would have reached a temperature of 450C. * Calculate mass of the copper sulphate solution: mass = volume x density = 25 x 1 = 25 g * Calculate change in temperature when the zinc is added:
ΔT = Tmaximum - Tminimum = 45 – 20 = 25 0C * Calculate the number moles of copper sulphate reacted: number of moles = concentration x volume = 0.5 x 0.025 = 0.0125 mol * Calculate energy released during the reaction (Q):
Q = mass of CuSO4 x specific heat capacity x ΔT = 25 x 4.2 x 25 = 2625 J * Calculate ΔH for the reaction (energy change is negative because the reaction was exothermic):
ΔH = -Q / number of moles = 2625 / 0.0125 = 210 kJmol-1
‘Absolute Uncertainty’ = abs/unc
‘Percentage Uncertainty’ = %unc
Uncertainty in mass = (%unc in density + %unc in volume) x mass
= (0 + 0.5/25) x 25 = ±0.5 g
Uncertainty in temperature change = abs/unc in Tmaximum + abs/unc in Tminimum
= 0.5 + 0.5 = ±1 oC
Uncertainty in number of moles = (%unc in concentration + %unc in volume) x number of moles
= (0 + 0.5/25) x 0.0125 = 0.00025 = ±0.0003 mol
Uncertainty in energy change = (%unc in mass + %unc in temperature change) x energy change
= (0.5/25 + 1/25) x 2625 = 157.5 = ±200 J
Uncertainty in ΔH = (%unc in energy change + %unc in number of moles) x ΔH
= (157.5/2625 + 0.00025/0.0125) x 210 = 16.8 = ±20 kJ/mol
Final Value of ΔH: -210 ± 20 kJmol-1
Conclusion
The accepted