In the materials, which tubes indicate that the deionized water did not contain contaminating starch or maltose?

In the materials, which tubes indicate that the deionized water did not contain contaminating starch or maltose?

• A. tubes 4, 5, and 6
• B. tubes 1, 2, and 3
• C. tubes 2, 3, and 4
• D. tubes 1, 3, and 5

Answer: (D)

The test checks for two possible contaminants: starch and maltose. When deionized water is truly clean, it should show no reaction with either test. The iodine test detects starch by turning blue-black if starch is present; without starch, the solution stays its normal color. The Benedict’s test detects reducing sugars like maltose by turning blue to green, yellow, orange, or red upon heating; if maltose isn’t present, the solution remains blue. So the tubes that show no color change in both tests indicate that the water did not contain contaminating starch or maltose.

The test checks for two possible contaminants: starch and maltose. When deionized water is truly clean, it should show no reaction with either test. The iodine test detects starch by turning blue-black if starch is present; without starch, the solution stays its normal color. The Benedict’s test detects reducing sugars like maltose by turning blue to green, yellow, orange, or red upon heating; if maltose isn’t present, the solution remains blue. So the tubes that show no color change in both tests indicate that the water did not contain contaminating starch or maltose.