Post on 08-Jan-2016
description
Chemical Reactions, cont’d
Absorbs energyReleases energy
Endothermic Reaction
Exothermic Reaction
What happens to energy in a reaction?
Reactants Products
Reaction energy (Q) = energy absorbed – energy released
Single bonds energies (kJ/mol)
CH4 H2ONH3
How much energy is contained in the bonds of the following molecules?
Double and triple bonds energies (kJ/mol)
What are some examples of endothermic and exothermic reactions?
CH4 + 2 O2 CO2 + 2 H2O
• How much energy is absorbed to break the bonds of the reactants during the chemical reaction?
• How much energy is released in the formation of the products?
• What is the reaction energy (Q)?• Is this reaction endothermic or exothermic?
+ 686 kJ
Ener
gy (k
J)
2 H2O 2 H2 + O2
• How much energy is absorbed to break the bonds of the reactants during the chemical reaction?
• How much energy is released in the formation of the products?
• What is the reaction energy (Q)?• Is this reaction endothermic or exothermic?
N2 + 3 H2 2 NH3
HCCH + 2 HF CH3CHF2
2 H2O + O2 2 H2O2
N2 + 3 H2 2 NH3
HCCH + 2 HF CH3CHF2
2 H2O + O2 2 H2O2
Combining reaction energy & stoichiometry
N2 + 2 O2 + 67.7 kJ 2 NO2
What amount of energy is required to produce 8 moles of NO2?
Combining reaction energy & stoichiometry
CH4 + 2 O2 CO2 + 2 H2O + 686 kJ
How much energy will be produced by the above reaction if 32 g of methane (CH4) react?
Combining reaction energy & stoichiometry
C + O2 CO2 + 393.5 kJ
The complete combustion of 1 mole of carbon releases 393.5 kJ of energy. To obtain 1000 kJ of energy, what mass of carbon will need to be burned?