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Energy changes in chem react

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2.00 g of sulphur were completely burnt in air. The heat given off raised thetemperature of 222 g of water from 21 degree celsius to 41 degree celsius.Calculate the enthalpy change of combustion of sulphur, in KJ mol^-1.( Relative atomic mass: S = 32.1; specific heat capacity of water = 4.18J g^-1 K^-1 )Ans: ... 顯示更多 2.00 g of sulphur were completely burnt in air. The heat given off raised thetemperature of 222 g of water from 21 degree celsius to 41 degree celsius.Calculate the enthalpy change of combustion of sulphur, in KJ mol^-1.( Relative atomic mass: S = 32.1; specific heat capacity of water = 4.18J g^-1 K^-1 )Ans: 297.9KJ mol^-1

最佳解答:

Energy given out = 222*4.18*(41-21) = 18559.2 J mol sulphur present = 2/32.1=0.062 mol so the enthalpy change = 18559.2/0.062 = 297875.16 J ≈ 297.9KJ/mol

其他解答:

note that the enthalpy change should be negative, i.e. exothermic.|||||Heat released = mcΔT = -(222)(4.18)(41 - 21) = -185559.2 J = -18.56kJ No. of moles of sulphur = 2 / 32.1 = 0.06231 mol Enthalpy change of combustion of sulphur = -18.56 / 0.06231 = -297.9 kJ mol^-1 2011-03-12 17:08:54 補充: Typing mistake: Heat released = -18559.2 J = -18.56kJ
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