Homework Help

How much CuO would you need to react with excess aluminum to generate same amout of...

user profile pic

sms409 | Student, Undergraduate | eNotes Newbie

Posted December 9, 2012 at 9:39 AM via web

dislike 1 like

How much CuO would you need to react with excess aluminum to generate same amout of heat as 139g of Fe2O3 does when reacted with excess aluminum? 

2Al + Fe2O3---> Al2O3 + 2Fe        delta H=-827kJ

2Al + 3CuO---> Al2O3 + 3Cu         delta H=-1170kJ

1 Answer | Add Yours

user profile pic

llltkl | College Teacher | (Level 3) Valedictorian

Posted December 9, 2012 at 2:59 PM (Answer #1)

dislike 1 like

Change in enthalpy is an extensive property. This implies that the amount of heat liberated is dependent upon the mass of the reactants. The stoichiometric relationships in respect of mass are

2Al (2x27g) + Fe2O3 (159.7g)---> Al2O3 + 2Fe        delta H=-827kJ

2Al (2x27g) + 3CuO (3x79.5)---> Al2O3 + 3Cu         delta H=-1170kJ

So, as per the first equation, 139g of Fe2O3, when reacted with sufficient aluminium would generate 139*827/159.7 = 719.8kJ of heat. Clearly, according to stoichiometric relations of the second equation, the same amount of heat shall be generated by 3x79.5x719.8/1170= 146.7g of CuO, when made to react with sufficient amount of aluminium.

Sources:

Join to answer this question

Join a community of thousands of dedicated teachers and students.

Join eNotes