Answer to Question #195904 in Chemistry for harmi

Question

How much energy in kJ is released when 10.21 g of aluminum react with an excess of copper oxide?

3 CuO + 2 Al -> 3 Cu + Al₂O₃  

△ H

 = 1190 kJ/mol

Answer 1

The balanced thermochemical equation:

3CuO + 2Al → 3Cu + Al₂O₃, △H = 1190 kJ/mol

 

The equivalences for this thermochemical equation are:

3 mol CuO ⇔ 2 mol Al ⇔ 3 mol Cu ⇔ 1 mol Al₂O₃ ⇔ +1190 kJ

Convert the amount of aluminum (Al) to moles:

10.21 g Al × (1 mol Al / 26.981 g Al) = 0.3784 mol Al

Use the thermochemical equation to determine the energy change:

0.3784 mol Al × (1190 kJ / 2 mol Al) = 225.15 kJ

Answer: 225.15 kJ of energy is released.