What is the standard enthalpy change of formation for elements in their standard
Practice Questions
Q1
What is the standard enthalpy change of formation for elements in their standard state?
0 kJ/mol
100 kJ/mol
298 kJ/mol
1 kJ/mol
Questions & Step-by-Step Solutions
What is the standard enthalpy change of formation for elements in their standard state?
Correct Answer: 0
Step 1: Understand what 'standard enthalpy change of formation' means. It refers to the heat change when one mole of a compound is formed from its elements in their standard states.
Step 2: Recognize 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: Identify the elements in their standard state. For example, oxygen is O2 gas, and carbon is solid graphite.
Step 4: Note that the standard enthalpy change of formation for any element in its standard state is defined as zero. This is because no heat is required to form an element from itself.
Step 5: Conclude that since the enthalpy change is zero, it means there is no energy change when an element is in its standard state.
