enthalpy change for a metal displacement reaction?

To determine the enthalpy change for a metal displacement reaction by adding a known mass of zinc powder to excess aqueous copper(II) sulfate solution and recording the rise in temperature.

Initial mass of weighing boat / g = 2.54

Mass of weighing boat and zinc / g = 4.57

Final mass of weighing boat / g = 2.55

Mass of zinc added / g = 2.02

Volume of aqueous CuSO4 used = 40 cm3

Temperature change / ºC = 29

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  • 1 month ago

    Supposing the specific heat and density of the copper solution to be the same as water:

    (4.184 J/g·°C) x (40 g) x (29°C) / (2.02 g Zn / (65.380 g Zn/mol)) = 157088 J/mol

    So:

    Zn(s) + CuSO4(aq) → Cu(s) + ZnSO4(aq), ΔH = -157 kJ

     [The minus sign did not come from the calculations. It is the convention for exothermic processes.]

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