Studied by 21 people
Define thermochemistry
the study of the energy changes that accompany physical and chemical changes in matter
Define thermal energy
the energy released by the surroundings in a chemical reaction as a result of the motion of the molecules
define a chemical system
a set of reactants and products being studyied in a chemical equation
Define surroundings
All matter around the system responsible for absorbing or releasing thermal energy - usually water
What happens when a reaction occurs?
heat (q) is transferred between the system and the surroundings
Define exothermic and endothermic
exothermic: the system releases energy to the surroundings (- delta h, but positive q) - reactants at higher energy than products - usually feel cold
Endothermic: The system absorbs energy from the surroundings (+delta h, but - q) - products at higher energy than reactans - usually feels hot
What happens when the surroundings absorb enegy from the system?
its temperature increases as well
Define open system, isolated system and closed system
Open system: a chemical reaction that produces gas - energy and matter can flow in and out of the system.
isolated system: neither matter nor energy can move in or out of the system
closed system: energy can move in or out of the system, but not matter - calorimeter.
How do you calculate heat transfer
using q=mct
where m is the mass in g, t is the change in temperature (final-initial) and c is the specific heat capacity of the surroundings (usually water)
what is the specific heat capacity for water
4.18 j/mol*ºC
what is the unit of q
Jules
How to convert Jules to KJ
divide by 1000
How to calculate mass given density
mass = volume * density in aqueous solutions
Define enthalpy change
the difference in enthalpy between reactants and products during a reaction. (delta H)
what is the relationship between q and delta H
when q is positive, delta H is negative
define molar enthalpy
the enthalpy change associated with a physical, chemical or nuclear change involving one mole of a substance (delta Hx)
how to calculate molar enthalpy
delta Hx = delta H/moles
