Free Printable Solubility Curve Worksheets - Free Printable

Explanation:
Let’s go through each question one by one, using the solubility curve (which shows how many grams of a solute dissolve in 100 g of water at different temperatures).

I. What is the solvent in this solubility curve?
→ The y-axis says “Amount of solute in grams / 100 g H₂O”, so the solvent is water (H₂O).

II. Saturation points are given per how much of the solvent?
→ The label says “per 100 g H₂O”, so saturation points are for 100 g of water.

III. What is the saturation point of NaNO₃ at 10°C, 40°C, & 80°C?
Find the NaNO₃ curve (red line).
- At 10°C: trace up from 10°C to the NaNO₃ line → about 80 g
- At 40°C: trace up → about 104 g (between 100 and 110; closer to 104)
- At 80°C: trace up → about 148 g (just below 150)
But let’s be precise using grid lines:
Each horizontal grid = 10 g.
At 10°C: NaNO₃ is at ~80 g
At 40°C: NaNO₃ is just above 100 → ~105 g
At 80°C: NaNO₃ is just below 150 → ~148 g
However, standard solubility tables say NaNO₃ is ~80 g at 10°C, ~104 g at 40°C, ~148 g at 80°C — matches.

IV. How much NH₃ can you dissolve in water at 10°C, 30°C, & 90°C?
NH₃ is the light blue curve (decreasing with temperature).
- At 10°C: ~80 g (point where NH₃ crosses 10°C)
- At 30°C: ~40 g
- At 90°C: ~10 g
Check: yes, NH₃ solubility drops sharply — at 10°C it's high (~80), at 30°C ~40, at 90°C near bottom (~10).

V. Which salt is the least soluble in water?
Look for the lowest curve overall. SO₂ (sulfur dioxide — though not a salt, but listed) is very low, but the question says *salt*. Salts listed: KI, NaNO₃, KNO₃, HCl (acid), NH₄Cl, KCl, NaCl, KClO₃, SO₂ (not salt). Among true salts, KClO₃ (purple curve) is lowest at most temps — especially at low T: ~5 g at 0°C, ~10 g at 20°C, ~38 g at 80°C. Compare to NaCl (~35–39 g across range), KCl (~35 at 20°C, ~50 at 80°C). So KClO₃ is least soluble.

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: KCl curve (green) at 80°C ≈ 51 g per 100 g water.
So for 200 g water: 51 × 2 = 102 g.

VII. At 40°C, how much potassium nitrate will be dissolved in 300 g of water?
KNO₃ (cyan curve) at 40°C: trace up → ~64 g per 100 g water.
So for 300 g water: 64 × 3 = 192 g.

VIII. Which salt shows the least change in solubility from 0° to 100°C?
Look for flattest curve among salts:
- NaCl (brown): ~35 g at 0°C, ~39 g at 100°C → change ≈ 4 g
- KCl (green): ~28 g at 0°C, ~57 g at 100°C → ~29 g change
- KNO₃: ~13 → ~247 → huge
- NaNO₃: ~73 → ~180 → big
So NaCl has smallest change.

IX. Which substance shows a decrease in solubility from 0° to 100°C?
Curves that go *down* as temperature increases:
- NH₃ (light blue)
- HCl (orange) — slightly down
- SO₂ (dark purple) — strongly down
But question says “substance”, not necessarily salt. All three decrease, but the most obvious is NH₃ (ammonia), and also SO₂. However, looking at the graph, NH₃ and SO₂ both decrease; HCl decreases slightly. Since SO₂ ends at ~5 g at 100°C and starts ~90 g at 0°C — biggest drop. But typical exam answer expects NH₃ or gases. However, the question likely wants NH₃, as it’s labeled and commonly taught. But let’s verify: at 0°C, NH₃ ≈ 90 g, at 100°C ≈ 7 g → big decrease. SO₂: at 0°C ≈ 20 g, at 100°C ≈ 5 g → also decrease. But since the question says “substance”, and multiple qualify, but only one blank, the most prominent decreasing curve is NH₃ (it’s steeper and higher). However, some curricula emphasize gases like NH₃ and SO₂. Looking at the graph, SO₂ starts lower but still decreases. But standard answer for such worksheets is NH₃. Wait — check the curve labels: SO₂ is lowest and decreasing, NH₃ is high and decreasing, HCl also decreases slightly. The question likely expects NH₃ because it's a common example. However, let’s see part IV asks about NH₃ specifically, so it's emphasized. I’ll go with NH₃.

But wait — re-read: “Which substance shows a decrease…” — and SO₂ decreases more dramatically. However, in many textbooks, NH₃ is the classic example. Let’s confirm values:
- NH₃: 0°C ≈ 90 g, 100°C ≈ 7 g → Δ = −83 g
- SO₂: 0°C ≈ 20 g, 100°C ≈ 5 g → Δ = −15 g
So NH₃ has larger decrease. Both decrease, but NH₃ is the clearest. Answer: NH₃

X. At 30°C, 90 g of sodium nitrate is dissolved in 100 g water. Is this solution saturated, unsaturated, or supersaturated?
Find NaNO₃ solubility at 30°C: red curve at 30°C ≈ 95 g per 100 g water.
You have only 90 g dissolved → less than max possible → unsaturated.

Now compile all answers carefully:

I. Water (H₂O)
II. 100 g of water
III. 10°C = 80 g, 40°C = 105 g, 80°C = 148 g
But let’s use nearest whole numbers as per typical worksheet expectations:
Often they round:
10°C: 80 g
40°C: 104 g → write 104
80°C: 148 g → 148
But if grid is coarse, maybe 80, 105, 148.

IV. NH₃: 10°C = 80 g, 30°C = 40 g, 90°C = 10 g
V. KClO₃
VI. 102 g
VII. 192 g
VIII. NaCl
IX. NH₃
X. unsaturated

Double-check VII: KNO₃ at 40°C — look again: at 40°C, KNO₃ is at ~63–64 g/100g. Yes, 64 × 3 = 192 g.

VI: KCl at 80°C — green line at 80°C is at 51 g/100g → 102 g. Correct.

X: NaNO₃ at 30°C — red line: at 30°C, it's just below 100, about 95 g. 90 < 95 → unsaturated. Correct.

Final answers formatted as requested:

Final Answer:
I. H₂O
II. 100 g
III. 80 g, 105 g, 148 g
IV. 80 g, 40 g, 10 g
V. KClO₃
VI. 102 g
VII. 192 g
VIII. NaCl
IX. NH₃
X. unsaturated