Chemistry

You add 7.326g of solid CaCl2 to 45.5 mL of water in a coffee cup calorimeter and measure as the temp. Increase from 22.6 C to 41.5 C. Specific heat water is 4.184 J/ g.C and the density of water is 0.9977 g/mL. Find the mass of water. PLEASE HELP ME!!!

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  1. Density = mass/Volume
    solving for mass
    mass = Density x Volume
    mass = (0.9977g/ml(45.5-ml) = 45.3953 grams.

    Are you sure 'mass of water' is all you needed? How about 'Heat of Reaction'?
    q=mc(delta Temp)
    q = (45.3953g)(4.184J/g-C)(41.5 - 22.6)C = 3589.7514joules
    = 3590joules (3 Sig-Figs)
    = 3.59Kj

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  2. I don't think you typed all of the problem/question.

    You get mass H2O from mass = volume x density and that will answer your posted question.

    However, most of these problems want to calculate delta H, usually in kJ/mol. That is done as follows:
    q = mass H2O x specific heat H2O x (Tfinal-Tinitial)

    Then delta H/g = q/7.326 g CaCl2.
    delta H/mol = (q/7.326) x molar mass CaCl2. This will be in J/mol. Convert to kJ/mol.

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