When pure sulfuric acid is dissolved in water, heat is evolved. In a laboratory

Question

When pure sulfuric acid is dissolved in water, heat is evolved. In a laboratory experiment to measure the molar heat of solution of sulfuric acid, the following procedure was followed. To a calorimeter containing 300 g of water at 20.00 oC, 10.65 g of H2SO4, also at 20.00 oC was added. The temperature change, which was monitored by a digital probe with negligible heat capacity, ceased when it reached a temperature of 26.55 oC. If the specific heat of the mixture is 4.184 J g–1 K–1, and the small heat capacity of the calorimeter is ignored, what is the heat evolved, per mole of sulfuric acid?

Select one:

a. –27.4 kJ mol-1

b. –72.8 kJ mol-1

c. –78.4 kJ mol-1

d. –84.6 kJ mol-1

Explanation / Answer

Mass of water and sulfuric acid = 300 + 10.65= 310.65

Temperature rise of mixture= 26.55-20 =6.55

Specific heat of mixture =4.184 K/g.k

Temperature rise = Mass* Specific heat * temperature difference= 310.65* 4.184*6.55 =8513.425 J=8.513 Kj

10 gms of H2SO4 corresponds to =10/98 moles ( Molecular weight of H2SO4=98)= 0.1020

Heat of reaction/ mole= 8.513/0.1020 =83.43 Kj/Mol

close answer is 84.6 Kj/Mole ( d is the correct answer)

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