2. When pure sulfuric acid dissolves in water, a great deal of heat is given off

Question

2. When pure sulfuric acid dissolves in water, a great deal of heat is given off. To measure it, 175 g of water was placed in a coffee cup calorimeter and chilled to 10.0 o C. Then, 4.90 g of sulfuric acid, also chilled to 10.0o C, was added, and the mixture was quickly stirred. The temperature rose rapidly to 14.9oC. Assume the specific heat of the solution is 4.18 J/g oC, and that ALL OF THE HEAT is absorbed by the solution. Calculate the heat evolved in kilojoules by the formation of the solution. Calculate the heat evolved per mole of sulfuric acid.

Explanation / Answer

  Atomic weights: H=1 S=32 O=16 H2SO4=98

175g H2O + 49.0g H2SO4 = 224g total solution (S)

14.9C - 10C = 4.9C

224gS x 4.9degC x 4.184J/g-degC = 4592 J for formation of solution

4592J/49gH2SO4 x 98gH2SO4/1molH2SO4 = 9185 J/mole enthalpy of solution

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