thermochem PDF

• What is energy defined as in thermochemistry?

  The capacity to do work or produce heat
• What does the law of conservation of energy state?

  Energy can be converted but not created or destroyed
• What are the two types of energy mentioned?

  Potential and kinetic energy
• How is potential energy defined?

  Due to position or composition, can convert to work
• What is an example of potential energy?

  Water behind a dam
• What is kinetic energy represented by in a formula?

  $KE =$$\frac{1}{2} mv^2$
• How does temperature relate to kinetic energy?

  Temperature reflects random motions of particles
• What does heat involve in thermochemistry?

  A transfer of energy due to temperature difference
• What is a system in thermochemistry?


  The focus of attention in a study
• What are surroundings in thermochemistry?


  Everybody else in the universe
• How is the universe defined in thermochemistry?

  Universe = System + Surroundings
• What characterizes an exothermic reaction?


  Heat flows out of the system
• What characterizes an endothermic reaction?


  Heat flows into the system
• What is enthalpy defined as?

  Enthalpy = heat
• What does ΔH represent in thermochemistry?

  Energy flow as heat at constant pressure
• How is the change in enthalpy calculated?

  ΔH = H products - H reactants
• What is molar enthalpy?

  An extensive property related to heat change
• How does changing coefficients affect heat change?


  Alters the heat change associated with a reaction
• What is calorimetry?

  • The science of measuring heat
  • Constant-pressure calorimeter (coffee cup)
  • Constant-volume calorimeter (bomb)
• What is heat capacity (C_p)?

  Heat absorbed per degree = J/°C or J/K
• What is specific heat capacity (c)?

  Heat capacity per gram = J/°C.g or J/K.g
• What is molar heat capacity?

  Heat capacity per mole = J/°C.mol or J/K.mol
• How are calorimeters used in measuring enthalpy changes?


  They measure energy released or absorbed by reactions
• What is the relationship between Q system and Q surrounding?

  Q system = -Q surrounding
• What is the equation for heat exchange?

  Q system + Q surrounding = 0
• What is the formula for calculating heat exchange?

  Q = mcΔT
• What is the principle of solution calorimetry?

  • Heat produced or consumed in the reaction (q reaction)
  • Heat absorbed or lost by the solution (q solution)
  • q reaction = -q solution
• How do you calculate the enthalpy change of dissolution for lithium chloride in a calorimeter?

  Use temperature rise and mass of water
• What is the heat of combustion per gram of phenol in a bomb calorimeter experiment?

  Calculate using temperature change and heat capacity
• What is Hess's Law?

  • Change in enthalpy is the same for one step or multiple steps
  • ΔH for overall reaction equals sum of individual steps
  • Enthalpy is a state function
• What happens to ΔH when a reaction is reversed?

  ΔH sign is changed
• What happens to ΔH when the coefficients of a reaction are multiplied?

  ΔH is multiplied by that integer
• What is standard enthalpy (ΔH_o)?

  Enthalpy change at standard conditions
• What is the standard heat of formation for an element?

  It is 0