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intramolecular forces
covalent bonds and ionic bonds
intermoleculer
dipole dipole, hydrogen bond, london diperian forces
intramolecular
the glue holding a molecule together.
intermolecular
the "Velcro" between different molecules—they affect boiling point, melting point, solubility, etc.
endothermic examples
photosynthesis, boiling points, melting points
exothermic examples
combustion
endothermic
more energy is required to break bonds than is released forming new ones
exothermic
more energy is released in bond formation than is required to break bonds
enthalpy depends on
-the reaction (products and reactants)
-the coefficents of the balanced equation
when chemical reactions or phase change occurs there is an enthalpy change because
the reactants and products have different enthalpies
endothermic has a (_) sign
+
what is the source of stored potential energy
chemical bonds
enthalpy change
the energy change of a balanced equation that occurs during a chemical reaction or phase change, reflecting the difference in enthalpy between products and reactants.
Molar enthalpy
the amount of energy absorbed or released per mole of a substance during a phase change at constant pressure.
Exothermic has more energy in bond
formation, so in the reactants
endothermic has more energy in
breaking (think ender's game he broke the system) so the products
combustion (exo) reacts and
ender (endo) breaks
heating something is
endothermic because heat needs to go into the system
breaking something is
endothermic because energy must go in to break the bonds
Photosynthesis points
-fuel for the cell resp process
-eventually can be transferred into fossil fuel
-energy originated from the sun
-6 CO2 + 6 H2O →C6H12O6 + 6O2 (water vapour though)
cellular respiration points
-exothermic
-reverse of photosynthesis
combustion
hydrocarbon fuel + oxygen → carbon dioxide and water
(sooooooo basically cell resp but with choose your own fuel)
When does combustion produce water vapour
in a closed or open system
when does combustion produce liquid water?
In an isolated system like a bomb calorimeter
decomp molar enthalapy is found by?
Reversing the polarity of the formation enthalpy in the data booklet
how can you determine if products or reactants have more EP?
energy potential diagrams
what are the x and y axis for EP diagrams?
y axis is EP in KJ, x axis is progress of rxn, the diff between the products n reactants is the delta H for that equation
what are the polyatomic elements?
P4 and S8
for ranking question, if postivie KJ
that means the system is gaining that much energy to form or decompose, so it would take more energy then a neg
calorimetry assumptions
the transfer of energy between the system and calorimeter is 100% efficient
no heat escapes the calorimeter
the specific heat capacity of a dilute solution is the same as water 4.19j/gc
the density of water is 1g/mL
explain simple, flame, and bomb caloriemetry
-a reaction takes place in a polysterence cup filled with water
-a fuel is burned below a metal contaniar filled with water
-a reaction takes place inside an enclosed vessel with surrounding sleeve filled with water
Activation energy
the minimum collision energy required for a reaction
Ea and delta H details
EA has to be positive, delta H can be negative, product-reactant vs mas e - reactant e
cataylsts
alternate pathway, decreases EA, delta H stays the same
modified hess law
products - reactant , elemtents are just 0