How many kilojoules are released when 8.2 g of water condenses at 100°C and cools to 15°C?

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Answer 1 · 2016-06-02T01:44:41

#-185,402 + (-2,913.46) = -188315.46 J#

#Q = 1.9 x10^5 J#

#Q = 1.9 x10^2 kJ#

There are two steps to this thermochemistry process

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First we are going to calculate the condensation process at #100^oC#.
Then calculate the cooling of the liquid from #100^oC to 15^oC#

Step 1 #Q = mC_p#

#Q = 8.2g (-2261 J/g) = -185,402 J#

Step 2 #Q = m(T_f-T_i)C_p#

#Q = 8.2g(15^o-100^oC)4.18J/(g^oC)= -2,913.46 J#

#-185,402 + (-2,913.46) = -188315.46 J#

#Q = 1.9 x10^5 J#

#Q = 1.9 x10^2 kJ#