What is the standard enthalpy change of formation for water (H2O) at 25°C?
Practice Questions
Q1
What is the standard enthalpy change of formation for water (H2O) at 25°C?
-285.83 kJ/mol
-241.82 kJ/mol
-393.5 kJ/mol
-241.0 kJ/mol
Questions & Step-by-Step Solutions
What is the standard enthalpy change of formation for water (H2O) at 25°C?
Step 1: Understand that the standard enthalpy change of formation is the energy change when one mole of a compound is formed from its elements in their standard states.
Step 2: Identify the elements that make up water (H2O), which are hydrogen (H) and oxygen (O).
Step 3: Note that the standard state for hydrogen is H2 gas and for oxygen is O2 gas.
Step 4: Write the balanced chemical equation for the formation of water: 2 H2(g) + O2(g) → 2 H2O(l).
Step 5: The standard enthalpy change of formation for one mole of water (H2O) is half of the value for the reaction, since the equation produces 2 moles of water.
Step 6: Look up the standard enthalpy change of formation for water, which is -241.82 kJ/mol.
