A sheet of gold weighing 8.8 g and at a temperature of 19.8 degree C is placed f

Question

A sheet of gold weighing 8.8 g and at a temperature of 19.8 degree C is placed flat on a sheet of iron weighing 22.0 g and at a temperature of 57.6 degree C. What is the final temperature of the combined metals? Assume that no heat is lost to the surroundings. Benzene (C6H6) bums in air to produce carbon dioxide and liquid water. Calculate the change in heat (in kilojoules) per gram of the compound reacted with oxygen. The standard enthalpy of formation of benzene is 49.04 kJ mol A 24.0-g sample of an unknown metal at 99 degree C was placed in a constant-pressure calorimeter containing 70.0 g of water at 24.0 degree C. The final temperature of the system was found to be 28.4 degree C. Calculate the specific heat of the metal. (The heat capacity of the calorimeter is 11.4 J/degree C.)

Explanation / Answer

specific heat, for gold =0.129 J/g degrees C

specific heat, for iron = 0.444 J/g degrees C

heat gain = heat lost

m of Au*c*(Tf-Ti) = - m of Fe*c*(Tf-Ti)

(8.8 g (0.129)(Tf-19.8 C) + (22.0g )(0.444)(Tf-57.6C)=0

(1.14 Tf - 22.48 ) + (9.768 Tf- 562.64 ) = 0

10.908 Tf = 585.12

Tf = 53.64 C

Temperature final = 51.70C

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