Free Printable Solubility Worksheets - Free Printable

Let’s solve this step by step using the solubility curve graph.

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Part A: Reading Solubility from the Graph

We need to find how many grams of each substance dissolve in 100 g of water at a given temperature — that’s what “solubility” means here.

We’ll go one question at a time, looking at the graph carefully.

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A1. What is the solubility of Na₂SO₄ at 90 °C?

- Find 90 °C on the x-axis (temperature).
- Go straight up until you hit the green line labeled “Na₂SO₄”.
- Look left to read the y-axis (solubility in g/100g water).
- At 90 °C, the Na₂SO₄ line is around 42 g.

✔ Answer: 42 g

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A2. What is the solubility of KNO₃ at 54 °C?

- Find 54 °C on x-axis (between 50 and 60).
- Go up to the red/brown line labeled “KNO₃”.
- Read across to y-axis.
- At 54 °C, it’s about halfway between 80 and 100 → maybe 85–90 g? Let’s be precise.
- At 50°C → ~80 g
- At 60°C → ~105 g
- So at 54°C → roughly 88 g

But let’s check again — actually, looking closely, at 54°C, KNO₃ is just under 90. Maybe 87 g? But since graphs are approximate, we can say ~88 g.

Wait — let me double-check standard values or typical graph readings. Actually, many versions of this graph show KNO₃ at 54°C as approximately 85 g. Hmm.

Actually, let’s interpolate:

From 50°C (80 g) to 60°C (105 g), that’s +25 g over 10 degrees → +2.5 g per degree.

So from 50 to 54 = 4 degrees → 4 × 2.5 = 10 g → 80 + 10 = 90 g

Yes! So 90 g is accurate.

✔ Answer: 90 g

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A3. What is the solubility of NaCl at 20 °C?

- Find 20 °C on x-axis.
- Go up to the flat gray line labeled “NaCl”.
- Read y-axis → it’s very close to 36 g.

Standard value for NaCl at 20°C is 36 g — matches graph.

✔ Answer: 36 g

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A4. What is the solubility of NaOH at 15 °C?

- Find 15 °C on x-axis.
- Go up to yellow line “NaOH”.
- At 10°C → ~100 g
- At 20°C → ~110 g
- So at 15°C → average → 105 g

Looking at graph, yes — it’s right in between.

✔ Answer: 105 g

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A5. What is the solubility of Pb(NO₃)₂ at 90 °C?

- Find 90 °C on x-axis.
- Go up to dark blue line “Pb(NO₃)₂”.
- Read y-axis → it’s at 120 g

Exactly on the line.

✔ Answer: 120 g

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Part B: Saturated, Unsaturated, Supersaturated?

Remember:
- If amount dissolved ≤ solubility → unsaturated (or saturated if equal)
- If amount > solubility → supersaturated (if stable) or precipitate forms — but usually called supersaturated if no precipitate yet.
- In these problems, they assume all is dissolved unless stated otherwise.

So compare given mass with solubility at that temp.

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B1. 50 g of NaCl is dissolved in 100 g of water at 20 °C.

- From A3, solubility of NaCl at 20°C = 36 g
- We have 50 g → which is MORE than 36 g → so it should be supersaturated? Wait — but NaCl doesn’t easily form supersaturated solutions. However, based purely on graph logic:

If more than solubility → supersaturated (assuming it’s dissolved without crashing out).

But technically, if you try to dissolve 50g in 100g water at 20°C, only 36g dissolves — rest stays solid → so solution is saturated, and extra is undissolved.

The question says: “is dissolved” — meaning ALL 50g is dissolved? That would be impossible normally — so likely they mean “attempted to dissolve”, and we judge based on capacity.

In most worksheets like this, if amount > solubility → supersaturated (even though unrealistic), OR sometimes they expect “saturated” if it’s at max.

Wait — let’s think logically.

Standard rule taught in schools:

- Amount < solubility → unsaturated
- Amount = solubility → saturated
- Amount > solubility → supersaturated (if dissolved) or saturated with precipitate

Since the problem says “is dissolved”, we assume it’s fully dissolved → so if > solubility → supersaturated.

But for NaCl, 50g > 36g → so supersaturated? That’s not physically common, but per worksheet logic...

Actually, let’s check other questions first.

Perhaps better to use strict comparison.

I recall in such worksheets, they often consider:

- If you put in less than max → unsaturated
- Equal → saturated
- More → supersaturated (even if unlikely)

So:

B1: 50g > 36g → supersaturated

But wait — I think there's a mistake. Let me re-read.

Actually, upon second thought — in reality, you cannot dissolve 50g NaCl in 100g water at 20°C — only 36g will dissolve. So the solution is saturated, and 14g remains undissolved. But the question says “is dissolved” — implying it *was* dissolved. So perhaps they want us to assume it’s possible → then supersaturated.

This is ambiguous.

Looking at similar worksheets online — they usually say:

> If the amount added is greater than the solubility, the solution is supersaturated (assuming no precipitation occurred).

So I’ll go with that.

✔ B1: supersaturated

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B2. 60 g of Pb(NO₃)₂ is dissolved in 100 g of water at 40 °C.

First, find solubility of Pb(NO₃)₂ at 40°C.

From graph: at 40°C, Pb(NO₃)₂ line is at about 75 g? Let’s see:

At 30°C → ~65 g
At 50°C → ~85 g
So at 40°C → ~75 g

Yes.

Given: 60 g < 75 g → so unsaturated

✔ B2: unsaturated

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B3. 80 g of NaOH is dissolved in 100 g of water at 10 °C.

Solubility of NaOH at 10°C: from graph, at 10°C → ~100 g? Wait no:

Earlier for A4, at 15°C it was 105g, at 10°C it should be lower.

Look at graph: at 0°C → ~95g? At 10°C → ~100g? Actually, let’s estimate:

At 0°C: ~98g
At 20°C: ~110g
So at 10°C: ~104g? Or maybe 100g?

Actually, looking at the yellow line — at 10°C, it’s about 100 g.

Given: 80 g < 100 g → unsaturated

✔ B3: unsaturated

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B4. 40 g of Na₂SO₄ is dissolved in 100 g of water at 30 °C.

Find solubility of Na₂SO₄ at 30°C.

Green line: at 30°C → it peaks around 45–50 g? Let’s see:

At 20°C → ~20g? No — wait, Na₂SO₄ has a weird curve.

Actually, from graph:

At 0°C → ~5g
At 10°C → ~10g
At 20°C → ~20g
At 30°C → ~45g (peak)
Then decreases after.

Yes — at 30°C, solubility is about 45 g.

Given: 40 g < 45 g → unsaturated

✔ B4: unsaturated

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B5. 120 g of KNO₃ is dissolved in 100 g of water at 60 °C.

Solubility of KNO₃ at 60°C: from graph, at 60°C → ~105–110 g? Earlier we said at 60°C it’s about 105g? Wait:

At 50°C → 80g
At 60°C → 105g
At 70°C → 130g?

Actually, standard value is ~110g at 60°C.

From graph: at 60°C, KNO₃ line is at about 110 g.

Given: 120 g > 110 g → supersaturated

✔ B5: supersaturated

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Now, compiling all answers:

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Final Answers:

A.
1. 42 g
2. 90 g
3. 36 g
4. 105 g
5. 120 g

B.
1. supersaturated
2. unsaturated
3. unsaturated
4. unsaturated
5. supersaturated

Note: For B1 and B5, even though supersaturation is unstable, per worksheet convention, we label them as such when amount exceeds solubility and it’s stated as “dissolved”.

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Final Answer:
A1: 42 g
A2: 90 g
A3: 36 g
A4: 105 g
A5: 120 g
B1: supersaturated
B2: unsaturated
B3: unsaturated
B4: unsaturated
B5: supersaturated