Multiple Choice
2. What observable change occurs when iodine comes into contact with starch?
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4. BONUS: Lab Techniques and Procedures
Test for Ions and Gases
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Which of the following elements can be isolated by electrolysis of aqueous NaCl?
A
Na
B
O_2
C
Cl_2
D
H_2
Verified step by step guidance1
Understand the process of electrolysis of aqueous NaCl, which involves passing an electric current through a solution of sodium chloride dissolved in water.
Identify the species present in the solution: Na^+ ions, Cl^- ions, H_2O molecules, and H^+ and OH^- ions from water dissociation.
Determine the possible products at the cathode (reduction site): either Na^+ ions can be reduced to Na metal, or H^+ ions from water can be reduced to H_2 gas. Since water is easier to reduce than Na^+, H_2 gas is typically produced.
Determine the possible products at the anode (oxidation site): either Cl^- ions can be oxidized to Cl_2 gas, or water molecules can be oxidized to O_2 gas. Because Cl^- ions are easier to oxidize than water, Cl_2 gas is typically produced.
Conclude that the element or molecule isolated by electrolysis of aqueous NaCl is Cl_2 gas, while Na metal is not isolated due to water reduction, and O_2 and H_2 are also possible but less favored compared to Cl_2 and H_2 respectively.
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