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When 3.0g of ethane, C2H6, is formed, 8.5 kJ of heat is produced.  What is the heat of...

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heyhello | Student, Grade 11 | eNotes Newbie

Posted June 5, 2011 at 12:35 AM via web

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When 3.0g of ethane, C2H6, is formed, 8.5 kJ of heat is produced.  What is the heat of formation of ethane.

2C+3H2 --> C2H6

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justaguide | College Teacher | (Level 2) Distinguished Educator

Posted June 5, 2011 at 12:52 AM (Answer #1)

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Heat of formation of a compound is the heat produced when one mole of the compound is produced.

The molar mass of ethane, which has a chemical formula of C2H6, is equal to 2*12 + 6*1 = 30 g/mol.

When 3 grams of ethane is formed the heat produced is 8.5 kJ.

3 grams of ethane is equal to 3/30 = 1/10 moles. As the formation of 0.1 moles of ethane requires 8.5 kJ, to produce 1 mole we require 10 times that amount or 10*8.5 = 85 kJ.

The heat of formation of ethane is 85 kJ/mol.

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