Which of the following statements best compares the energy required for two separate…
CHEMISTRY · Single correct · A Level · Chemistry · Bonding · Bonding
Problem
Which of the following statements best compares the energy required for two separate changes of water at 25 °C and 1 atm?
I. Vaporizing liquid water to steam
II. Decomposing water to H₂(g) and O₂(g)
A student claims that the two processes require similar amounts of energy per mole. Which statement is most accurate?
(a) Process I requires more energy because hydrogen bonding in water is stronger than the covalent O–H bonds that must be broken in Process II.
(b) Process II requires orders of magnitude more energy because breaking the O–H covalent bonds consumes far more energy than overcoming the intermolecular forces disrupted in Process I.
(c) Process II actually releases energy overall because the gases formed have lower potential energy than liquid water.
(d) Process II requires only about twice as much energy as Process I, since the energy needed is distributed over the three moles of gas produced in the reaction.