What is the standard enthalpy of formation for elements in their standard state?
Practice Questions
Q1
What is the standard enthalpy of formation for elements in their standard state?
0 kJ/mol
1 kJ/mol
100 kJ/mol
Not defined
Questions & Step-by-Step Solutions
What is the standard enthalpy of formation for elements in their standard state?
Correct Answer: 0 kJ/mol
Step 1: Understand what 'standard enthalpy of formation' means. It is the energy change when one mole of a compound is formed from its elements in their standard states.
Step 2: Know what 'standard state' means. The standard state of an element is its most stable form at 1 atmosphere of pressure and a specified temperature (usually 25 degrees Celsius).
Step 3: Recognize that for any element in its standard state (like O2 gas for oxygen, or Na solid for sodium), the formation of that element from itself does not require energy.
Step 4: Conclude that because no energy is needed to form an element from itself, the standard enthalpy of formation for elements in their standard state is defined as 0 kJ/mol.
