Final answer:
The correct answer to the student's question about the result of electrolysis of water is that the gases produced are elements, specifically hydrogen and oxygen.
Step-by-step explanation:
Kelly ran electricity through a sample of water using electrolysis. The water changed into two gases, X and Y. Which statement is best supported by this evidence? The correct answer is B. The gases X and Y are elements.
During the electrolysis of water, water, which is a reactant compound, is decomposed into hydrogen and oxygen gases. These gases are elements, and the process can be represented by the balanced chemical equation: 2 H₂O(l) → 2 H₂(g) + O₂(g). This shows that water is composed of two elements, hydrogen (H₂) and oxygen (O₂), both of which are diatomic molecules when in gas form.
Hence, the statement that gases X and Y are elements is best supported by the evidence of electrolysis, as it breaks down the compound water into its elemental gases, hydrogen and oxygen.