Interpreting Solubility Curve worksheet with a graph showing solubility of different substances versus temperature.

Here is the complete solution to the worksheet “Interpreting Solubility Curve”:

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1. Define solubility.

> Solubility is the maximum amount of a solute (in grams) that can dissolve in a specific amount of solvent (usually 100 g of water) at a given temperature to form a saturated solution.

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2. Using the solubility curve below, answer the given questions.

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I. What is the solvent in this solubility curve?

> Water (H₂O)
> *Explanation:* The y-axis says “Amount of solute in grams / 100 g H₂O”, which means water is the solvent used for all measurements.

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II. Saturation points are given per how much of the solvent?

> 100 grams of water (H₂O)
> *Explanation:* All values on the y-axis are expressed as “grams of solute per 100 g H₂O”, so saturation points are standardized to 100 g of water.

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III. What is the saturation point of NaNO₃ at 10°C, 40°C, & 80°C?

> - 10°C = 80 g
> - 40°C = 105 g
> - 80°C = 148 g *(approx — curve peaks just under 150 g)*
> *Explanation:* Locate NaNO₃ (red line). At each temperature, go up to the curve and read the y-value (grams/100g H₂O).

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IV. How much NH₃ can you dissolve in water at 10°C, 30°C, & 90°C?

> - 10°C = 70 g
> - 30°C = 45 g
> - 90°C = 15 g
> *Explanation:* NH₃ (blue line) has decreasing solubility with increasing temperature. Read values from the curve at each temperature.

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V. Which salt is the least soluble in water?

> KClO₃ (Potassium chlorate)
> *Explanation:* Look for the curve that stays lowest across most temperatures. KClO₃ (purple line) starts near 5 g at 0°C and only reaches ~50 g at 100°C — lower than others like NaCl, KCl, etc.

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VI. How many grams of potassium chloride can be dissolved in 200 g of water at 80°C?

> 100 grams
> *Explanation:* First, find solubility of KCl (green line) at 80°C → ~50 g per 100 g water.
> So for 200 g water: 50 g × 2 = 100 g

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VII. At 40°C, how much potassium nitrate will be dissolved in 300 g of water?

> 150 grams
> *Explanation:* Find KNO₃ (cyan line) at 40°C → ~50 g per 100 g water.
> For 300 g water: 50 g × 3 = 150 g

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

> NaCl (Sodium chloride)
> *Explanation:* The NaCl (brown line) is nearly flat — from ~35 g at 0°C to ~39 g at 100°C. Very little change compared to others like KNO₃ or NaNO₃.

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IX. Which substance shows a decrease in solubility from 0° to 100°C?

> NH₃ (Ammonia), SO₂ (Sulfur dioxide), and HCl (Hydrogen chloride)
> *Explanation:* These three curves slope downward as temperature increases. Of these, NH₃ is most commonly referenced as a gas whose solubility decreases with temperature.

> *(Note: If only one answer is expected, choose NH₃, as it’s the most prominent example.)*

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

> Supersaturated
> *Explanation:* At 30°C, the solubility of NaNO₃ (red line) is ~95 g per 100 g water. Since 90 g < 95 g, the solution is actually unsaturated.
> ❗ Correction: I made an error. Let me recheck the graph.

> ✔ Revised Answer: Unsaturated
> At 30°C, NaNO₃ solubility ≈ 95 g/100g H₂O. You’ve dissolved only 90 g → less than maximum → unsaturated.

> *(If the value were above 95 g, it would be supersaturated. But 90 g is below the curve.)*

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✔ Final Answers Summary:

1. Solubility = max grams of solute per 100 g solvent at a given temp.
2. I. Water (H₂O)
II. 100 g H₂O
III. 10°C=80g, 40°C=105g, 80°C=148g
IV. 10°C=70g, 30°C=45g, 90°C=15g
V. KClO₃
VI. 100 g
VII. 150 g
VIII. NaCl
IX. NH₃ (and also SO₂, HCl — but NH₃ is primary)
X. Unsaturated

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