7285 art A A calorimeter contains 18.0 ml, of water at 135 °C. When 210 g of X (

Question

7285 art A A calorimeter contains 18.0 ml, of water at 135 °C. When 210 g of X (a substance with a molar mass of 420g/mol) is added, it dissolves via the reaction X(s) +Ho0)+X(a) and the temperature of the solution increases to 28 5 °C Calculate the enthalpy change, for this reaction per mole of X heat of the resulting solution is equal to that of water 4.18J/)that densily of water is 1,00 g/ml. and that no heat is lost to the caloimeter Rselt, nor Express the change in enthalpy in kilojoules per mole to three significant figures. Hints k.J/mol

Explanation / Answer

no of mol of X dissolved = 2.1/42 = 0.05 mol

amount of heat released(q) = m*s*DT

       m = mass of mixer = 18+2.1 = 20.1 g

       s = specific heat of water = 4.184 j/g.c

       DT = 28.5-13.5 = 15

    q = 20.1*4.184*15

      = 1.261 kj

DHrxn = -q/n

        = -1.261/0.05

        = -25.22 kj/mol

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