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Choosing Indicators for a Rinse Decision 4 questions
Choosing Indicators for a Rinse Decision
Base your answers on the information provided and your knowledge of chemistry. Use the 2025 Chemistry Reference Tables as needed.
A print studio tests a clear rinse. The model uses indicators with sharp color changes at the listed pH values. Below its boundary each indicator has the lower-pH color. At or above the boundary it has the higher-pH color.
| Indicator | Boundary pH | Color below boundary | Color at or above boundary |
|---|---|---|---|
| P | 5 | Yellow | Blue |
| Q | 7 | Red | Green |
| R | 6 | Clear | Purple |
A sample turns P blue and Q red. The studio wants to know whether its pH is at least 6.
Question 1
What pH range is established by P and Q together?
- Below 5
- At least 5 and below 7
- At least 6 and below 7
- At least 7
Question 2
Explain how indicator R can resolve the studio’s decision on a fresh portion of the same rinse.
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Another sample turns P yellow and Q red. Its R reading is purple. Assume the sample portions have the same pH.
Question 3
Explain which readings are incompatible in the model and why.
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Question 4
Describe one check using a known pH sample that could test one of the conflicting indicator readings.
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