8.1.1 Standard Enthalpy Changes

• What is the standard enthalpy change denoted by?

  $ΔH°$
• The standard enthalpy change is measured when one mole of a substance reacts under standard conditions.
• Standard conditions are defined as 298 K (25 °C) and 100 kPa (1 bar).
• What is the standard enthalpy change for the combustion of methane?

  -890 kJ/mol
• Standard enthalpy changes refer to the enthalpy change when one mole of a substance reacts under standard conditions.
• Match the type of standard enthalpy change with its definition:

  Standard Enthalpy of Formation ↔️ Formed from its elements

  Standard Enthalpy of Combustion ↔️ Completely burned in oxygen

  Standard Enthalpy of Neutralisation ↔️ Neutralises one mole of alkali
• What is the standard temperature in Kelvin for thermochemical calculations?

  298 K
• The standard pressure in thermochemistry is 100 kPa
• Using standard conditions ensures consistency and comparability in thermochemical calculations.
• What is the standard temperature in Celsius for thermochemical calculations?

  25 °C
• What are the two key conditions for standard enthalpy changes?

  298 K and 100 kPa
• The standard enthalpy change for the combustion of methane is -890 kJ/mol under standard conditions.
• The standard enthalpy change is often expressed in kJ/mol
• What is the standard value of pressure in thermochemistry?

  100 kPa
• What is the standard temperature in Kelvin for standard enthalpy change calculations?

  298 K
• The standard pressure for standard enthalpy change is 100 kPa.
• The standard enthalpy change measures the energy transferred when one mole of a substance reacts.
• What are the units commonly used to express standard enthalpy change?

  kJ/mol
• The standard enthalpy change $ΔH°$ occurs when one mole of a substance reacts.
• Standard conditions for enthalpy change calculations include 298 K and 100 kPa.
• Match the type of standard enthalpy change with its definition:

  Standard Enthalpy of Formation ↔️ Enthalpy change when one mole of a substance is formed from its elements in their standard states

  Standard Enthalpy of Combustion ↔️ Enthalpy change when one mole of a substance is completely burned in oxygen

  Standard Enthalpy of Neutralisation ↔️ Enthalpy change when one mole of an acid neutralises one mole of an alkali
• What is the equation for the formation of water from hydrogen and oxygen in standard enthalpy of formation?

  $H₂(g) +$$½ O₂(g) → H₂O(l)$
• The standard enthalpy of combustion is the enthalpy change when one mole of a substance is completely burned in oxygen.
• The standard enthalpy of neutralisation involves the reaction of an acid with an alkali.
• What is the definition of standard enthalpy of formation?

  Formed from its elements
• Standard conditions are a reference set of temperature and pressure used in thermochemistry.
• The standard temperature in thermochemistry is 298 K.
• What is the standard pressure in thermochemistry in kPa?

  100 kPa
• The standard pressure for thermochemistry is 100 kPa.
• Standard conditions include a temperature of25 °C and a pressure of 100 kPa.
• What is the standard temperature in degrees Celsius for standard enthalpy change calculations?

  25 °C
• Steps for calculating standard enthalpy change of combustion for methane:

  1️⃣ Write the balanced equation

  2️⃣ Identify the standard conditions

  3️⃣ Find the enthalpy change value
• What is the standard temperature in thermochemistry in Kelvin?

  298 K
• The standard temperature in thermochemistry is equal to 25 °C
• What is the standard pressure in thermochemistry in kilopascals?

  100 kPa
• The standard temperature in thermochemistry is 298 K.
• The standard pressure in thermochemistry is 100 kPa.
• What are standard conditions used for in thermochemistry?

  Reference temperature and pressure
• The standard temperature is 298 K
• What is the standard pressure in thermochemistry in bar?

  1 bar