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Calculating energy changes
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Calculating energy changes
Exothermic reactions give out heat
If the energy given out is more than it needs to break the bonds the reaction is exothermic.
Endothermic reaction take in heat
Energy change= Total energy needed to break all bonds-total energy given out when new bonds are formed
Example CH4 + 2O2----> CO2 + 2H20
4*C-H=(4*412)=1648kj
2*O=O =(2*496)=992kj
Total energy in = 2640kj
Bonds formed are C=O and O-H
2*C=O =(2*743)=1486kj
4* O-H =(4*463) =1852kj
Total energy out=3338kj
Total energy change= 2640-3338=-698kj
- Exothermic reaction
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- GCSE C2 Mind Map on Calculating energy changes, created by danielberthaur on 02/01/2014.
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