Interpreting Solubility Curve worksheet with a graph and questions about solubility of different substances at various temperatures.

Let's go through each question step by step using the solubility curve provided.

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1. Define solubility.

Solubility is the maximum amount of a solute that can dissolve in a given amount of solvent at a specific temperature to form a saturated solution. It is usually expressed in grams of solute per 100 grams of solvent (e.g., g/100g H₂O).

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2. Using the solubility curve, answer the following questions:

#### I. What is the solvent in this solubility curve?

The solvent is water (H₂O).
This is indicated by the label "Amount of solute in grams / 100 g H₂O" on the y-axis.

✔ Answer: Water

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

The solubility values are given per 100 grams of water, as shown on the y-axis.

✔ Answer: 100 g of water

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

We look at the NaNO₃ curve (the red line) and read the corresponding solubility values:

- At 10°C: ~80 g/100g H₂O
- At 40°C: ~100 g/100g H₂O
- At 80°C: ~150 g/100g H₂O

✔ Answer:
- 10°C = 80 g
- 40°C = 100 g
- 80°C = 150 g

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

Look at the NH₃ curve (purple line):

- At 10°C: ~90 g/100g H₂O
- At 30°C: ~60 g/100g H₂O
- At 90°C: ~10 g/100g H₂O

Note: Ammonia solubility decreases with increasing temperature.

✔ Answer:
- 10°C = 90 g
- 30°C = 60 g
- 90°C = 10 g

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#### V. Which salt is the least soluble in water?

We compare all curves at any temperature (e.g., at 20°C). The lowest curve is SO₂ (sulfur dioxide), which has very low solubility.

✔ Answer: SO₂

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

First, find solubility of KCl at 80°C from the graph:
- KCl curve shows about 50 g/100g H₂O at 80°C.

Now scale up for 200 g water:
$$
\frac{50\ \text{g}}{100\ \text{g H}_2\text{O}} \times 200\ \text{g H}_2\text{O} = 100\ \text{g}
$$

✔ Answer: 100 g

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

Find solubility of KNO₃ at 40°C:
- From graph: ~60 g/100g H₂O

Now for 300 g water:
$$
\frac{60\ \text{g}}{100\ \text{g H}_2\text{O}} \times 300\ \text{g H}_2\text{O} = 180\ \text{g}
$$

✔ Answer: 180 g

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

Look for the flattest curve between 0°C and 100°C.

- NaCl (sodium chloride) has a nearly flat curve — its solubility changes very little.
- Others like KNO₃ or KClO₃ increase sharply.

✔ Answer: NaCl

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

Look for a curve that goes down as temperature increases.

- NH₃ (ammonia) and SO₂ both show decreasing solubility.
- But NH₃ is more prominent.

✔ Answer: NH₃ (or SO₂) — but NH₃ is the most notable.

> However, based on the graph, NH₃ clearly decreases from ~90 g at 0°C to ~10 g at 90°C.

✔ Best Answer: NH₃

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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?

Check solubility of NaNO₃ at 30°C:
- From graph: ~100 g/100g H₂O

Since 90 g < 100 g → it can dissolve more.

So, the solution is unsaturated.

✔ Answer: Unsaturated

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✔ Final Answers Summary:

| Question | Answer |
|--------|--------|
| I | Water |
| II | 100 g of water |
| III | 10°C: 80 g; 40°C: 100 g; 80°C: 150 g |
| IV | 10°C: 90 g; 30°C: 60 g; 90°C: 10 g |
| V | SO₂ |
| VI | 100 g |
| VII | 180 g |
| VIII | NaCl |
| IX | NH₃ |
| X | Unsaturated |

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