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intro chem HELp please

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1. Zinc is often used to calibrate calorimeters because it undergoes a very sharp phase transition from the solid to the liquid at 419.5oC. Calculate the enthalpy change when 5 g of zinc metal is heated from 100oC to the point where the entire sample is melted. (The heat of fusion for zinc is 112.4 J/g and its specific heat capacity is 0.388 J/goC.)

2. A 235 gram block of iron is heated to 450 °C and then is dropped into a coffee cup calorimeter containing 250 g of water at 25.0 °C. What is the final temperature of the system to the nearest 0.1 °C? (Assume all heat is transferred to the water)

Specific heat capacity of iron = 0.451 J/(g*°C)

Specific heat capacity of water = 4.18 J/(g*°C)

  • intro chem HELp please - ,

    q1 for Zn to move from 100 C to 419.5 C.
    q1 = mass Zn x specific heat x (Tfinal-Tinitial).

    q2 = heat to melt Zn
    q2 = mass Zn x delta Hfusion.

    Total heat = q1 + q2

    For the iron,
    heat lost by iron + heat gained by water = 0.

    [mass Fe x specific heat Fe x (Tfinal-Tinitial)] + [mass water x specific heat water x (Tfinal-Tinitial)] = 0
    Solve for Tfinal.

  • intro chem HELp please - ,


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