ch 5

• What is thermochemistry the study of?

  Energy associated with chemical reactions
• What is energy defined as in thermochemistry?

  Capacity to do work or produce heat
• What is the formula for kinetic energy?

  KE = ½ mv²
• What does 'm' represent in the kinetic energy formula?

  Mass of the object in kg
• What does 'v' represent in the kinetic energy formula?

  Velocity of the object in m/s
• What is the formula for potential energy?

  PE = mgh
• What does 'g' represent in the potential energy formula?

  Acceleration due to gravity (9.8 m/s²)
• What does 'h' represent in the potential energy formula?

  Height of the object in meters
• What are the four types of energy mentioned in thermochemistry?

  Kinetic, potential, chemical, thermal energy
• How do you calculate the kinetic energy of an electron with mass $9.11 \times 10^{-31} \text{ kg}$ moving at $1.59 \times 10^{20} \text{ m/s}$?


  KE = $1.15 \times 10^{7} \text{ kJ}$
• What is the potential energy of a radioactive particle weighing $7.20 \times 10^{3} \text{ ng}$ found $110 \text{ m}$ above the earth's surface?


  PE = $7.77 \times 10^{6} \text{ J}$
• What does the first law of thermodynamics state?

  Energy cannot be created or destroyed
• What is a system in thermodynamics?

  The chemical reaction being studied
• What is the definition of surroundings in thermodynamics?

  Everything not in the system
• What is heat (q) in thermodynamics?

  Flow of thermal energy between objects
• How does heat flow between objects of different temperatures?

  From higher temp. object to lower temp. object
• What does work (w) represent in thermodynamics?

  Movement of molecules against a force
• How is internal energy defined?

  Total energy from kinetic and potential energy
• What is the equation relating heat and work to internal energy?

  ΔE = q + w
• What is the formula for work done in terms of pressure and volume?

  w = -PΔV
• What is enthalpy in thermodynamics?

  Heat released or absorbed during a reaction
• How can enthalpy and heat be treated at constant pressure?

  They can be treated as the same variable
• What is the internal energy of a system at constant pressure of 20.0 atm with a volume change from 10L to 5L releasing 92.2 kJ of heat?

  -82.07 kJ
• What are state functions in thermodynamics?

  Functions depending on the current state
• Which properties are considered state functions?

  H, E, P, V
• What are extensive properties in thermodynamics?

  Properties proportional to the amount of substance
• What is an endothermic reaction?

  Absorbs thermal energy from surroundings
• What happens to molecules during an endothermic reaction?

  Molecules speed up and break bonds
• What is an exothermic reaction?

  Releases thermal energy to surroundings
• What happens to molecules during an exothermic reaction?

  Molecules slow down and form bonds
• What does a positive enthalpy change indicate?

  Heat gain in an endothermic reaction
• What does a negative enthalpy change indicate?

  Heat loss in an exothermic reaction
• How do you calculate the enthalpy change for a reaction?

  ΔH = reactants - products
• What is the enthalpy change for the formation of ammonia from hydrogen and nitrogen?

  -105 kJ
• What do thermochemical equations include?

  Enthalpy of reaction
• How many grams of MgO are produced during an enthalpy change of -375 kJ?

  25.11 g MgO
• How do you calculate the enthalpy change for the reaction of methane with chlorine gas?

  ΔH = bonds broken - bonds formed
• What is the enthalpy change for the combustion of 15.0 g of ethanol?

  -181 kJ
• How much heat is released when 5.0 g of H₂O₂ decomposes?

  -14.4 kJ
• What is heat capacity?

  Heat required to change temperature of substance