Chemistry 30 diploma prep- thermochemistry

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35 Terms

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intramolecular forces

covalent bonds and ionic bonds

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intermoleculer

dipole dipole, hydrogen bond, london diperian forces

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intramolecular

the glue holding a molecule together.

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intermolecular

the "Velcro" between different molecules—they affect boiling point, melting point, solubility, etc.

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endothermic examples

photosynthesis, boiling points, melting points

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exothermic examples

combustion

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endothermic

more energy is required to break bonds than is released forming new ones

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exothermic

more energy is released in bond formation than is required to break bonds

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enthalpy depends on

-the reaction (products and reactants)
-the coefficents of the balanced equation

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when chemical reactions or phase change occurs there is an enthalpy change because

the reactants and products have different enthalpies

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endothermic has a (_) sign

+

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what is the source of stored potential energy

chemical bonds

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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.

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Molar enthalpy

the amount of energy absorbed or released per mole of a substance during a phase change at constant pressure.

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Exothermic has more energy in bond

formation, so in the reactants

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endothermic has more energy in

breaking (think ender's game he broke the system) so the products

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combustion (exo) reacts and

ender (endo) breaks

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heating something is

endothermic because heat needs to go into the system

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breaking something is

endothermic because energy must go in to break the bonds

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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)

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cellular respiration points

-exothermic

-reverse of photosynthesis

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combustion

hydrocarbon fuel + oxygen → carbon dioxide and water
(sooooooo basically cell resp but with choose your own fuel)

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When does combustion produce water vapour

in a closed or open system

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when does combustion produce liquid water?

In an isolated system like a bomb calorimeter

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decomp molar enthalapy is found by?

Reversing the polarity of the formation enthalpy in the data booklet

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how can you determine if products or reactants have more EP?

energy potential diagrams

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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

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what are the polyatomic elements?

P4 and S8

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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

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calorimetry assumptions

  1. the transfer of energy between the system and calorimeter is 100% efficient

  2. no heat escapes the calorimeter

  3. the specific heat capacity of a dilute solution is the same as water 4.19j/gc

  4. the density of water is 1g/mL

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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

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Activation energy

the minimum collision energy required for a reaction

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Ea and delta H details

EA has to be positive, delta H can be negative, product-reactant vs mas e - reactant e

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cataylsts

alternate pathway, decreases EA, delta H stays the same

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modified hess law

products - reactant , elemtents are just 0