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)

CH 4 H 2 ONH 3 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?

CH O 2  CO H 2 O 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? kJ

Energy (kJ)

2 H 2 O  2 H 2 + O 2 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?

N H 2  2 NH 3 HCCH + 2 HF  CH 3 CHF 2 2 H 2 O + O 2  2 H 2 O 2

N H 2  2 NH 3

HCCH + 2 HF  CH 3 CHF 2

2 H 2 O + O 2  2 H 2 O 2

Combining reaction energy & stoichiometry N O kJ  2 NO 2 What amount of energy is required to produce 8 moles of NO 2 ?

Combining reaction energy & stoichiometry CH O 2  CO H 2 O kJ How much energy will be produced by the above reaction if 32 g of methane (CH 4 ) react?

Combining reaction energy & stoichiometry C + O 2  CO kJ The complete combustion of 1 mole of carbon releases kJ of energy. To obtain 1000 kJ of energy, what mass of carbon will need to be burned?