8.1.2 Measuring Enthalpy Changes

• Enthalpy change ($ΔH$) measures the heat energy transferred during a chemical reaction at constant pressure
• Exothermic reactions release heat and have a negative enthalpy change.
• What type of enthalpy change is associated with endothermic reactions?

  Positive
• Match the characteristic with the type of reaction:

  Releases heat ↔️ Exothermic

  Absorbs heat ↔️ Endothermic
• Enthalpy change ($ΔH$) measures the heat energy transferred during a chemical reaction at constant pressure
• Exothermic reactions release heat and have a negative enthalpy change.
• What type of enthalpy change is associated with endothermic reactions?

  Positive
• Match the characteristic with the type of reaction:

  Releases heat ↔️ Exothermic

  Absorbs heat ↔️ Endothermic
• What is the standard temperature for measuring enthalpy changes?

  298 K
• The standard pressure for measuring enthalpy changes is 100 kPa.
• The standard concentration for solutions in enthalpy measurements is 1 mol/dm³
• What does enthalpy change ($ΔH$) measure?


  Heat energy transferred
• Exothermic reactions have a positive enthalpy change.

  False
• An example of an exothermic reaction is the combustion of hydrogen
• Give an example of an endothermic reaction.

  Formation of nitric oxide
• Match the characteristic with the type of reaction:

  Releases heat ↔️ Exothermic

  Absorbs heat ↔️ Endothermic
• The standard pressure for measuring enthalpy changes is 1 atm.
• What is the standard temperature in Celsius for enthalpy measurements?

  25°C
• Calorimetry is used to measure the amount of heat transferred in a chemical change.
• Match the component of a calorimeter with its function:

  Thermometer ↔️ Measures temperature change

  Stirrer ↔️ Ensures uniform temperature

  Insulated container ↔️ Reduces heat loss
• What is the formula for calculating heat change in calorimetry?

  $q =$$mcΔT$
• Calorimetry relies on isolating the system from its surroundings
• The specific heat capacity of a substance is measured in J/g°C.
• Enthalpy change measures the heat energy transferred to or from a system during a chemical reaction at constant pressure
• Exothermic reactions have a positive enthalpy change.

  False
• Endothermic reactions absorb heat from the surroundings, leading to a positive enthalpy change, $ΔH > 0$, and a decrease in temperature
• What is the enthalpy change for the reaction $2H_{2}(g) +$$O_{2}(g) \rightarrow 2H_{2}O(l)$?


  $ΔH =$$- 572 \text{ kJ / mol}$
• Match the characteristic with the type of reaction:

  Releases heat ↔️ Exothermic reaction

  Absorbs heat ↔️ Endothermic reaction
• What is the standard temperature for measuring enthalpy changes?

  $298 \text{ K}$
• Standard conditions for measuring enthalpy changes include a pressure of 100 kPa.
• Calorimetry is used to measure the amount of heat transferred during a chemical or physical change
• What is the purpose of the stirrer in a calorimeter?

  Ensure uniform temperature
• What is the formula for calculating heat change in calorimetry?

  $q =$$mcΔT$
• Calorimetry can be used to calculate the enthalpy change of a reaction.
• Steps for measuring enthalpy change in solution reactions using a calorimeter

  1️⃣ Prepare the calorimeter

  2️⃣ Record initial temperature

  3️⃣ Add reactants

  4️⃣ Monitor temperature change

  5️⃣ Calculate enthalpy change
• Enthalpy change in solution reactions refers to the heat released or absorbed when reactants are mixed in a solvent
• What does $q$ represent in the formula $q =$$mcΔT$?


  Heat absorbed or released
• In the formula $q =$$mcΔT$, $m$ refers to the mass of the reactants.


  False
• The term $ΔT$ in the formula $q =$$mcΔT$ represents the change in temperature
• What is the specific heat capacity of water in J / g°C?

  4.18