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Comparing Two Model Dye Baths at Neutral pH 4 questions
Comparing Two Model Dye Baths at Neutral pH
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A fabric class models two dye baths with different dissolved ingredients. Both begin at pH 7.0 at 25 °C. The class wants to know which bath changes pH less if a small amount of base enters. It adds equal amounts of the same dilute base to equal volumes of the baths.
| Bath | pH before adding base | pH after adding base |
|---|---|---|
| P | 7.0 | 9.0 |
| Q | 7.0 | 7.2 |
Question 1
Which conclusion is supported by the results?
- Bath P was more acidic before the test.
- Bath Q was more basic before the test.
- Bath Q changed pH less after the addition.
- Baths P and Q changed pH by the same amount.
Question 2
In this model, the hydrogen ion concentration in mol/L equals 10 raised to the power −pH. By what factor did this concentration decrease in bath P?
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The class proposes that bath Q contains dissolved particles that react with some of the added OH-. Bath P contains almost none of those particles.
Question 3
Explain how the proposed reaction could account for the smaller pH rise in Q.
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The class adds a second equal dose of base to bath Q. After this dose, the pH is 8.8.
Question 4
Does bath Q resist the second addition as well as it resisted the first? Compare the two pH changes to support your answer.
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