Chemistry worksheet designed to help students practice reading solubility curves, determining saturation levels, and calculating solute mass at various temperatures.

Let’s go step by step through each problem using the solubility curve graph.

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Problem 1: Find mass of solute that dissolves in 100 mL water at given temps

We read the graph: find temperature on x-axis, go up to the curve, then left to y-axis (grams per 100 g H₂O — which is same as 100 mL for water).

1. KNO₃ at 70°C
→ Go to 70°C on x-axis, go up to KNO₃ curve, then left to y-axis.
→ It hits about 130 g

2. NaCl at 100°C
→ NaCl curve is almost flat. At 100°C, it’s around 40 g

3. NH₄Cl at 90°C
→ Go to 90°C, up to NH₄Cl curve, left to y-axis → about 70 g

4. Which is most soluble at 15°C?
Check all three curves at 15°C:
- KNO₃: ~25 g
- NaCl: ~35 g
- NH₄Cl: ~30 g
→ So NaCl is most soluble at 15°C

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Problem 2: Saturated or Unsaturated? How much more can dissolve?

Remember: If amount dissolved < solubility limit → unsaturated. Difference = how much more can dissolve.

a) 70g NaNO₃ in 100mL at 30°C
→ Solubility of NaNO₃ at 30°C ≈ 95g
→ 70g < 95g → Unsaturated
→ Can dissolve 95 - 70 = 25g more

b) 50g NH₄Cl in 100mL at 50°C
→ Solubility of NH₄Cl at 50°C ≈ 50g
→ Exactly at limit → Saturated
→ No more can dissolve → 0g more

c) 20g KClO₃ in 50mL at 50°C
→ First, note: this is in 50mL, not 100mL.
→ Solubility of KClO₃ at 50°C ≈ 20g per 100mL → so in 50mL, max = 10g
→ But we have 20g in 50mL → that’s double the limit!
Wait — actually, if solubility is 20g/100mL, then in 50mL, only 10g can dissolve.
So 20g added → 10g will dissolve, 10g will settle → solution is saturated, and no more can dissolve.
But question says “contains 20g” — does that mean dissolved or total? In context, usually means dissolved unless stated otherwise. But 20g cannot fully dissolve in 50mL at 50°C.
Actually, let’s check graph: KClO₃ at 50°C is about 20g per 100g water → so in 50g water, max 10g.
If solution contains 20g dissolved in 50mL → impossible. Probably typo or misread.
Wait — maybe it’s 20g in 50mL meaning total added? But question says “contains”, likely meaning dissolved.
Better interpretation: if 20g is dissolved in 50mL, but solubility is only 10g per 50mL → that would be supersaturated, which is unstable. But typically, we assume it’s what’s dissolved.
Actually, looking back: the table says “a solution that contains 20g of KClO₃ at 50°C (in 50 mL H₂O)” — this likely means 20g is present, but not necessarily all dissolved. But in standard problems, “contains” often means dissolved. However, since 20g > 10g (max for 50mL), it must be saturated with excess solid. So solution is saturated, and no more can dissolve → 0g more

But let’s double-check: perhaps the 20g is the amount dissolved? Then it’s impossible — so probably the problem intends for us to compare to the solubility scaled to 50mL.

Solubility of KClO₃ at 50°C = 20g / 100mL → so for 50mL, saturation point is 10g.
If solution has 20g dissolved → that’s not possible; it would precipitate. So likely, the solution is saturated with 10g dissolved, and 10g undissolved. But the question says “contains 20g” — ambiguous.

In many textbooks, when they say “a solution contains X g in Y mL”, they mean X g is dissolved. But here, 20g in 50mL exceeds solubility. So perhaps it's a trick.

Alternative: maybe I misread the graph. Let me recheck KClO₃ at 50°C.

Looking at graph: KClO₃ curve at 50°C is at about 20g per 100g water. Yes.

So for 50mL water, max dissolved = 10g.

If the solution "contains" 20g, it probably means 20g was added, but only 10g dissolved → so the solution is saturated, and no more can dissolve. Answer: Saturated, 0g more

d) 70g KI at 0°C in 200mL H₂O
→ Solubility of KI at 0°C ≈ 130g per 100mL → so for 200mL, max = 260g
→ 70g < 260g → Unsaturated
→ Can dissolve 260 - 70 = 190g more

Wait — is KI solubility really 130g at 0°C? Looking at graph: KI curve starts high. At 0°C, KI is about 130g/100mL? Actually, looking closely: at 0°C, KI is around 128-130g. Yes.

So for 200mL, capacity = 2 * 130 = 260g. 70g is less → unsaturated, can add 190g more.

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Problem 3: Solubility values

a) KCl at 5°C → ~28g
b) KCl at 25°C → ~35g
c) Ce₂(SO₄)₃ at 10°C → ~10g (it decreases with temp)
d) Ce₂(SO₄)₃ at 50°C → ~5g

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Problem 4: 10g KCl in 100g water at 90°C — saturated or unsaturated?

Solubility of KCl at 90°C ≈ 55g per 100g water
10g < 55g → Unsaturated

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Problem 5: 100g NaNO₃ in 100g water at 80°C

a) Solubility of NaNO₃ at 80°C ≈ 150g → 100g < 150g → Unsaturated

b) As cooled, when does solid first appear? When solubility drops to 100g.
Find temp where NaNO₃ solubility = 100g → look at graph: around 35°C?
At 30°C, NaNO₃ is ~95g, at 40°C ~105g → so about 35°C.
Answer: Around 35°C, because that’s when the solution becomes saturated and any further cooling causes precipitation.

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Problem 6: Most soluble at 20°C? Least at 40°C?

At 20°C: check all curves. Highest is KI (~140g?), wait no — KI is high, but let's see:

Actually, at 20°C:
- KI: ~140g? Wait, graph shows KI starting at 130 at 0°C, going up. At 20°C, maybe 145g?
But also NaNO₃ at 20°C is ~85g, KNO₃ ~30g, etc.

Wait, KI is highest at low temps. At 20°C, KI is about 145g, NaNO₃ about 85g, so KI is most soluble.

Least at 40°C: look for lowest curve at 40°C. Ce₂(SO₄)₃ is very low, about 5g. KClO₃ is about 15g, so Ce₂(SO₄)₃ is least.

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Problem 7: Least soluble at 10°C?

At 10°C: Ce₂(SO₄)₃ is about 10g, KClO₃ about 5g? Wait, KClO₃ at 10°C is about 5g, Ce₂(SO₄)₃ about 10g. So KClO₃ is lower?

Check graph: at 10°C, KClO₃ curve is below Ce₂(SO₄)₃? Actually, Ce₂(SO₄)₃ starts higher and decreases. At 10°C, Ce₂(SO₄)₃ is about 10g, KClO₃ is about 5g. So KClO₃ is less soluble.

But let's confirm: some graphs show Ce₂(SO₄)₃ decreasing from 20g at 0°C to 5g at 100°C. At 10°C, maybe 18g? I need to be careful.

Looking at typical solubility curves: Ce₂(SO₄)₃ has negative slope, starts around 20g at 0°C, goes down. KClO₃ starts low, increases slowly.

At 10°C:
- KClO₃: ~5g
- Ce₂(SO₄)₃: ~18g (if it decreases from 20 at 0°C to 5 at 100°C, then at 10°C it's still high)
Actually, upon second thought, in many standard graphs, at 10°C, Ce₂(SO₄)₃ is about 10-12g, KClO₃ is about 5g. So KClO₃ is less soluble.

But let's see the graph provided: the user's image shows Ce₂(SO₄)₃ curve starting at about 20g at 0°C and decreasing to near 0 at 100°C. At 10°C, it might be 18g. KClO₃ at 10°C is about 5g. So KClO₃ is less soluble.

However, sometimes Ce₂(SO₄)₃ is plotted lower. To be precise, based on common data, at 10°C, KClO₃ solubility is approximately 5g/100mL, while Ce₂(SO₄)₃ is about 10g/100mL. So KClO₃ is least soluble at 10°C.

But wait — in the graph, there's also NH₃, but it's a gas, and its solubility decreases, but at 10°C it's high. We're comparing solids probably.

The substances listed are mostly salts. At 10°C, the lowest curve is KClO₃.

Confirming with standard knowledge: yes, KClO₃ has low solubility at low temps.

So answer: KClO₃

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Now, compiling final answers:

Final Answer:
1.
- KNO₃ at 70°C = 130 g
- NaCl at 100°C = 40 g
- NH₄Cl at 90°C = 70 g
- Most soluble at 15°C = NaCl

2.
- 70g NaNO₃ at 30°C: Unsaturated, 25g more
- 50g NH₄Cl at 50°C: Saturated, 0g more
- 20g KClO₃ at 50°C in 50mL: Saturated, 0g more (since max 10g can dissolve in 50mL)
- 70g KI at 0°C in 200mL: Unsaturated, 190g more

3.
a) KCl at 5°C = 28 g
b) KCl at 25°C = 35 g
c) Ce₂(SO₄)₃ at 10°C = 10 g
d) Ce₂(SO₄)₃ at 50°C = 5 g

4. Unsaturated

5.
a) Unsaturated
b) Around 35°C, because that's when solubility equals 100g/100mL, so cooling below that causes crystallization.

6.
- Most soluble at 20°C: KI
- Least soluble at 40°C: Ce₂(SO₄)₃

7. KClO₃