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# Chapter 6

### Thermochemistry (Test 3)

Question | Answer |
---|---|

thermodynamics | the study of energy and its transformations |

thermochemistry | the study of the relationship between chemical reactions and energy |

energy | the capacity to do work |

heat | the flow of energy caused by a temperature difference |

work | the result of a force acting through a distance |

What is the equation for work involving force and distance? | w = F times d |

What is the equation for work involving pressure and volume? | w = - P (delta V) |

kinetic energy | the energy associated with the motion of an object |

What is the equation for kinetic energy? | Ek = (1/2)(m)(V^2) |

potential energy | stored energy; energy due to position or composition (examples: chemical energy) |

thermal energy | energy associated with the temperature of a substance |

chemical energy | energy associated with the relative positions of electrons and nuclei in atoms and molecules |

system | the part of the universe being studied |

surroundings | everything else in the universe |

internal energy of the system (E) | the sum total of all of the kinetic and potential energies of every particle in the system; unknowable |

state function | a function that is independent of the history or path followed |

What are some examples of state functions? | temperature, volume of a gas, location, molarity, internal energy, enthalpy, and change in any of these. |

What is one joule equal to? | 1 (kg * m^(2))/(s^(2)) |

What is the First Law of Thermodynamics? | the law of conservation of energy; the total energy of the universe is constant. |

What is the equation that expresses the First Law of Thermodynamics? | delta E = q + w, where delta E is the change in internal energy, q is heat, and w is work. |

How do you determine if the sign of q is positive or negative? | q is positive if heat flows from the surroundings to the system; q is negative if heat flows from the system to the surroundings. w is positive if the surroundings do work on the system; w is negative if the system does work on the surroundings. |

calorimetry | measuring heat flow |

calorimeter | an instrument used for measuring heat flow |

bomb calorimeter | a constant volume calorimeter delta E = q sub v, where q sub v is heat flow under constant volume |

coffee-cup calorimeter | a constant pressure calorimeter delta H = q sub p, where q sub p is heat flow under constant pressure |

heat capacity | the amount of heat required to raise the temperature of a substance by 1 degree Celsius |

specific heat capacity | the amount of heat required to raise the temperature of 1 g of a substance by 1 degree Celsius |

What is the equation for heat? | q =(m)(c)(delta T) |

When a problem involves two substances, how do you determine heat? | -q = q |

In a bomb calorimeter (constant volume), what equation is used? | delta E = q sub v |

How many joules are equal to 1 liter*atmosphere? | 101.3 J = 1 L*atm |

delta H | enthalpy change; heat flow under constant pressure |

An endothermic reaction has which sign of delta H? | positive |

An exothermic reaction has which sign of delta H? | negative |

The stoichiometric coefficients in a thermochemical reaction refer to what? | the number of moles of reactants and products |

A reversed reaction has what effect on the delta H of that reaction? | changes the sign |

The enthalpy change, delta H, is for what? | the specified number of moles |

What is Hess's Law? | the total enthalpy change (delta H) for a process is the same regardless of whether the process occurs in one step or many steps |

What is a formation reaction? | forming one mole of a substance from its elements in their most stable forms |

Any element in its most stable form has what enthalpy of formation? | 0 |

To find delta H of a reaction using delta H of formations, always do what? | delta H formation of products - delta H formation of reactants |