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Checking a Color Change After Water Loss 4 questions
Checking a Color Change After Water Loss
Base your answers on the information provided and your knowledge of chemistry. Use the 2025 Chemistry Reference Tables as needed.
A classroom model tracks a dissolved coloring agent. A sample initially absorbs strongly at 520 nm. After water evaporates, its color looks darker. The class restores the lost water to the original volume and compares that sample with a second one that received a light treatment.
| Sample | Volume when tested (mL) | Wavelengths with strong absorption (nm) |
|---|---|---|
| Original | 50 | 520 |
| Evaporated, then restored | 50 | 520 |
| Light treated, then restored | 50 | 445 and 520 |
Question 1
Which result gives evidence beyond a simple change in concentration of the original coloring agent?
- The initial sample is 50 mL.
- The evaporated and restored sample absorbs at 520 nm.
- The restored light-treated sample has a strong band at 445 nm.
- All samples are measured at the same final volume.
Question 2
Explain how restoring the evaporated sample to 50 mL helps test whether its darkening was due to water loss.
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A student suggests that the empty cell or water might also give a reading at 445 nm.
Question 3
Describe a blank measurement that could check the student’s suggestion.
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Question 4
If the blank has no 445 nm band, what does that tell you about the light-treated result? Explain why an additional chemical test would still be useful.
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