🧪 Chemistry Quiz 9: Thermochemistry and Enthalpy

🧪 Chemistry · Quiz 009

Connect heat flow and enthalpy with calorimetry, state functions, and a formation-enthalpy calculation for methane combustion.

Learning goalInterpret and calculate enthalpy changes using calorimetry, Hess’s law, and standard formation data.

  • 5 questions
  • Advanced connections
  • Explanations after finishing
Answered 0/5
FoundationWhat sign does ΔH have for an exothermic process written in the forward direction?
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The system releases heat to the surroundings.

UnderstandingWhich statement correctly relates enthalpy to heat transfer?
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State the condition under which ΔH equals measured heat.

ApplicationHow much heat is absorbed by 100.0 g of water when its temperature rises by 5.0 °C? Use c = 4.184 J/(g·°C).
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Use q = mcΔT and convert joules to kilojoules.

InterpretationWhy can Hess’s law be used to add enthalpy changes from several reaction steps?
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Consider whether enthalpy depends on the path.

ConnectionFor CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l), use ΔHf° values in kJ/mol: CH₄ = −74.87, CO₂ = −393.51, H₂O(l) = −285.83, O₂ = 0. What is ΔH°?
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Subtract the reactant formation-enthalpy sum from the product sum.

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