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Following Calcium Through a Resin 4 questions
Following Calcium Through a Resin
Base your answers on the information provided and your knowledge of chemistry. Use the 2025 Chemistry Reference Tables as needed.
A model water softener contains a resin with four charged sites. Each site starts with two Na+ ions and can hold one Ca2+ or one Mg2+ ion in their place. The model passes two equal water portions through the same resin. The entering water contains no sodium. Ions missing from the water stay on the resin, and ions added to the water come from the resin.
| Portion | Ion | Units entering | Units leaving |
|---|---|---|---|
| 1 | Ca2+ | 4 | 0 |
| 1 | Mg2+ | 0 | 0 |
| 1 | Na+ | 0 | 8 |
| 2 | Ca2+ | 0 | 2 |
| 2 | Mg2+ | 4 | 2 |
| 2 | Na+ | 0 | 0 |
Question 1
Which ion occupies sites on the resin after the first portion that it did not occupy before?
- Ca²⁺
- Mg²⁺
- Na⁺
- Neither Ca²⁺ nor Mg²⁺
Question 2
Complete the table with the units of each ion held by the resin at the end of each water portion. Show how you used the water readings.
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Question 3
A technician says the resin no longer exchanged ions in portion 2 because no sodium appeared. Evaluate that claim using the charges and both divalent ion records.
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A sensor can report only the total number of Ca2+ and Mg2+ units in a water portion. It cannot distinguish calcium from magnesium.
Question 4
Compare this sensor’s entering and leaving readings for portion 2. Identify one ion the technician could measure separately to reveal the exchange.
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