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Constant-Volume Calorimetry quiz

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  • What is the heat of combustion?
    It is the amount of heat released when one mole of a substance is burned or combusted.
  • Which elements are most commonly involved in combustion reactions?
    Carbon, hydrogen, and oxygen are most commonly involved in combustion reactions.
  • What device is used to measure the heat released during a combustion reaction at constant volume?
    A bomb calorimeter is used to measure the heat released during a combustion reaction at constant volume.
  • Why is the bomb calorimeter described as having constant volume?
    Because its steel container does not expand during the combustion reaction, keeping the volume fixed.
  • What is the standard enthalpy of combustion symbolized as?
    It is symbolized as ΔH°comb.
  • How is the standard enthalpy of combustion related to the heat lost by the reaction?
    It is equal to the negative of the heat lost by the reaction (ΔH°comb = -Qlost).
  • What is the main purpose of the stirrer in a bomb calorimeter?
    The stirrer ensures that the heat released is evenly distributed throughout the water.
  • What role do the wires (fuses) play in a bomb calorimeter?
    They ignite the combustion reaction inside the calorimeter.
  • How is the temperature change during the reaction measured in a bomb calorimeter?
    A thermometer is used to measure the temperature change of the water.
  • What formula relates the heat gained by the calorimeter to its heat capacity and temperature change?
    The formula is Q = CΔT, where C is the heat capacity and ΔT is the temperature change.
  • What does it mean if Q is positive in the context of calorimetry?
    A positive Q means that heat is gained by the calorimeter and water.
  • Why is a combustion reaction considered exothermic?
    Because it releases heat to the surroundings.
  • What happens to the heat released by the sample in a bomb calorimeter?
    The heat is transferred to the water and the calorimeter, raising their temperature.
  • How is the heat lost by the reaction related to the heat gained by the calorimeter and water?
    The heat lost by the reaction equals the heat gained by the calorimeter and water.
  • What is the constant volume formula for standard enthalpy of combustion in a bomb calorimeter?
    ΔH°comb = positive MCAT + heat capacity × change in temperature (ΔH°comb = MCΔT + CΔT).