Solubility Curves, Solutions & Molarity Answer Keys | PDF ... - Free Printable

Let's analyze and solve each question step by step based on the provided solubility curve graph.

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1. Which salt is least soluble in water at 20°C?

- From the graph, we observe the solubility of each salt at 20°C.
- At 20°C:
- KClO₃ (potassium chlorate) has the lowest solubility among all the salts shown.
- Answer: KClO₃

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2. How many grams of potassium chloride (KCl) can be dissolved in 200 g of water at 80°C?

- First, find the solubility of KCl at 80°C from the graph.
- At 80°C, the solubility of KCl is approximately 50 g/100 g H₂O.
- To find the amount of KCl that can dissolve in 200 g of water:
\[
\text{Solubility in 200 g H₂O} = 50 \, \text{g/100 g H₂O} \times 2 = 100 \, \text{g}
\]
- Answer: 100 g

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3. At 40°C, how much potassium nitrate (KNO₃) can be dissolved in 300 g of water?

- First, find the solubility of KNO₃ at 40°C from the graph.
- At 40°C, the solubility of KNO₃ is approximately 60 g/100 g H₂O.
- To find the amount of KNO₃ that can dissolve in 300 g of water:
\[
\text{Solubility in 300 g H₂O} = 60 \, \text{g/100 g H₂O} \times 3 = 180 \, \text{g}
\]
- Answer: 180 g

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4. Which salt shows the least change in solubility from 0°C to 100°C?

- Observe the slopes of the solubility curves for all salts between 0°C and 100°C.
- NaCl (sodium chloride) has the flattest slope, indicating the least change in solubility over this temperature range.
- Answer: NaCl

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5. At 30°C, 90 g of sodium nitrate (NaNO₃) is dissolved in 100 g of water. Is this solution saturated, unsaturated, or supersaturated?

- First, find the solubility of NaNO₃ at 30°C from the graph.
- At 30°C, the solubility of NaNO₃ is approximately 70 g/100 g H₂O.
- Since 90 g of NaNO₃ is dissolved in 100 g of water, and the solubility is only 70 g/100 g H₂O, the solution contains more solute than it can hold at 30°C.
- Answer: Supersaturated

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6. A saturated solution of potassium chlorate (KClO₃) is formed from one hundred grams of water. If the saturated solution is cooled from 80°C to 50°C, how many grams of precipitate are formed?

- First, find the solubility of KClO₃ at 80°C and 50°C.
- At 80°C, the solubility of KClO₃ is approximately 150 g/100 g H₂O.
- At 50°C, the solubility of KClO₃ is approximately 20 g/100 g H₂O.
- In a saturated solution at 80°C, 100 g of water dissolves 150 g of KClO₃.
- When cooled to 50°C, only 20 g of KClO₃ can remain dissolved in 100 g of water.
- The amount of KClO₃ that precipitates is:
\[
\text{Precipitate} = 150 \, \text{g} - 20 \, \text{g} = 130 \, \text{g}
\]
- Answer: 130 g

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7. What compound shows a decrease in solubility from 0°C to 100°C?

- Observe the solubility curves for all salts.
- NH₃ (ammonia) shows a downward trend, indicating a decrease in solubility as the temperature increases.
- Answer: NH₃

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8. Which salt is most soluble at 10°C?

- From the graph, observe the solubility of each salt at 10°C.
- At 10°C, KI (potassium iodide) has the highest solubility among all the salts shown.
- Answer: KI

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9. Which salt is least soluble at 50°C?

- From the graph, observe the solubility of each salt at 50°C.
- At 50°C, KClO₃ (potassium chlorate) has the lowest solubility among all the salts shown.
- Answer: KClO₃

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10. Which salt is least soluble at 90°C?

- From the graph, observe the solubility of each salt at 90°C.
- At 90°C, NH₃ (ammonia) has the lowest solubility among all the salts shown.
- Answer: NH₃

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Final Answers:

1. KClO₃
2. 100 g
3. 180 g
4. NaCl
5. Supersaturated
6. 130 g
7. NH₃
8. KI
9. KClO₃
10. NH₃

Boxed Final Answer:
\[
\boxed{KClO_3, 100 \, \text{g}, 180 \, \text{g}, \text{NaCl}, \text{Supersaturated}, 130 \, \text{g}, \text{NH}_3, \text{KI}, \text{KClO}_3, \text{NH}_3}
\]