Powdered Zinc Reaction with Copper(II) Sulfate Solution
2. Powdered zinc was reacted with 25.00cm3 of 1.000moldm−3 copper(II) sulfate solution in an insulated beaker. Temperature was plotted against time.
(i) Estimate the time at which the powdered zinc was placed in the beaker. [1]
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(ii) State what point Y on the graph represents. [1]
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(b) (i) The maximum temperature used to calculate the enthalpy of reaction was chosen at a point on the extrapolated (dotted) line. State the maximum temperature which should be used and outline one assumption made in choosing this temperature on the extrapolated line. [2]
Maximum temperature: ........................................................................................................................................................................................................................
Assumption: .....................................................................................................................................................................................................................................
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(ii) To determine the enthalpy of reaction the experiment was carried out five times. The same volume and concentration of copper(II) sulfate was used but the mass of zinc was different each time. Suggest, with a reason, if zinc or copper(II) sulfate should be in excess for each trial. [1]
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(iii) The formula q = mcΔT was used to calculate the energy released. The values used in the calculation were m = 25.00g, c = 4.18Jg−1K−1.
State an assumption made when using these values for m and c. [2]
Value Assumption:
m = 25.00g ..............................................................................................................................................................................................................................
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c = 4.18Jg−1K−1 ..............................................................................................................................................................................................................
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(iv) Predict, giving a reason, how the final enthalpy of reaction calculated from this experiment would compare with the theoretical value. [2]
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