1. How much heat (in kJ) is evolved (under standard conditions) when 184.78 g of
ID: 698803 • Letter: 1
Question
1. How much heat (in kJ) is evolved (under standard conditions) when 184.78 g of copper reacts to form copper(II) oxide?
2. How much heat (in kJ) is evolved when 60.26 g of water cools and freezes from 59.63oC to 0oC?
3. What is the change in enthalpy (in kJ) under standard conditions when 8.186 g of ethane is combusted?
4. What is the enthalpy of combustion (in kJ/mol) for acetone (CH3COCH3) under standard conditions (water is produced as a liquid)? Use the appendix in your textbook, do not enter units, and answer with 5 significant digits.
Explanation / Answer
The equation is as follows:
2 Cu + O2 2 CuO
The mass of copper is 184.78 g.
Moles = 184.78 g x 1 mol/ 63.546 g
= 2.91 mol
From the equation, 1mol Cu = 1 mol CuO
The heat of formation of CuO is -157.3 kJ of heat when one mol of Cu is burned.
-157.3 kJ/ mol x 2.91 mol = -458 kJ CuO
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