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Coffee Calorimetry Problem

  1. Oct 15, 2011 #1
    1. The problem statement, all variables and given/known data
    The reaction of 0.050 g of solid Mg with 100.0 mL of 1.00M aqueous HCl solution is carried out in a coffe-cup calorimeter. The temperature of the solution increases from 22.21 degrees Celsius to 24.46 degrees Celsius. How much heat is produced by the reaction?


    2. Relevant equations
    Q = m*c*Δt

    Mg + 2HCl → MgCl2 + H2

    3. The attempt at a solution
    mols Mg = .002057
    mols HCl = .1
    Limiting Reactant = Mg
    Δt = 2.25 degrees Celsius

    I am confused since there is no water involved in the reaction. Assumptions I was given are:
    1. The specific heat/molar heat of a calorimeter is small and can be ignored.
    2. The specific heat/molar heat of a dilute aqueous solution is the same as that of water, c = 4.184 J/g°C.
    3. The densities of dilute aqueous solutions are approximately 1.00 g/mL.

    I believe I am to use the Q = mct equation. I know the specific heat, c, should be 4.184, and that the change in temperature is 2.25 degrees Celsius. However, I am not sure what to put for m, the mass. Should m be the total mass of everything or just the mass of the substances actually used in the reaction that takes place?
     
  2. jcsd
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