Midterm review- Kinetics/Energetics Flashcards
Exothermic Reaction: Chemicals gain or lose enthalpy
Lose enthalpy
Exothermic: Heat energy lost or gained?
Lost
Exothermic: Surrounding temperature?
Hotter
Exothermic: Delta H?
Negative
Exothermic: Reactants or Products?
H of reactants > H of products
Endothermic: Gain or lose enthalpy?
Gain
Endothermic: Heat energy lost of gained?
Gained
Endothermic: surrounding temperature?
Colder
Endothermic: Delta H?
Positive
Endothermic: Reactants or Products?
H of products > H of reactants
Spontaneous Reactions
Occur without heating when mixing reagents
Enthalpy (H)
energy contained in chemical bonds that can be converted into heat
Factors affecting enthalpy
value of deltaH, concentration of reactants, states of reactants and products, temperature of reactions, pressure of reaction
Ways to find enthalpy change
Hess’s law, bond enthalpies, and delta Hs of formations
Bond enthalpies
(Sum of BEs of reactants) minus (Sum of BEs of products)
Delta Hs of formations
(Sum of Delta Hs of products) minus (Sum of Delta Hs of reactants)
Multiply by coefficients
Elements in standard state = 0
Ways to measure Reaction Rates
- Mass or volume changes for gaseous reactions
- Change in pH for acid/base reactions
- Change in conductivity for electrolytes
- Use of spectrometer for color change reactions
Collision Theory must…
…take place for reactions to occur
3 Parts of Collision Theory
- The two particles must collide
- The two particles must collide so that the reactive parts hit
- The reactive parts must hit with sufficient energy (activation energy)
Activation Energy
minimum amount of energy required to bring about a reaction
Factors affecting Reaction Rates
- Temperature: increases frequency of collisions
- Catalyst: lowers activation energy
- Surface Area of reactants: increases chances of collisions
- Concentration of reactants: increases amount of collisions
