Lab Procedure and Data Tables

Upload or link the lab handout/manual page first. I need the actual lab instructions to write a correct step-by-step procedure and the right blank data tables.

Once you attach it, I’ll give you:

1. a simple, specific procedure rewritten in plain English
2. blank data tables for all measurements/observations you need to collect
3. any quick notes on what to watch out for during the lab

If you want, you can also paste the lab text here directly.

Yes — with the PDF and your screenshots, there’s enough to write out a simple procedure and the blank tables.

This lab is basically: make serial dilutions, mix the ions for AX and BY_2, watch for whether a precipitate forms, and calculate Q_{sp} for each trial. Then you use the trial that is closest to “just forms precipitate / just saturated” to estimate K_{sp} for each salt. The slides specifically say to record the starting ion concentrations, calculate Q_{sp} at the instant of mixing, and note whether precipitation happened for each trial.

Simple procedure

Part 1: Before starting

1. Get the stock solutions:

   • 0.50 M A(NO_3)_2
   • 0.50 M K_2X
   • 0.332 M B(NO_3)_2
   • 0.50 M KY
     These are the given starting solutions shown in the slides for AX and BY_2.

2. Label containers or wells for:

   • AX dilution trials
   • AX reaction trials
   • BY_2 dilution trials
   • BY_2 reaction trials

3. Make a plan to keep careful notes for every dilution and every reaction mixture, because your report must be specific about how each dilution and mixture was prepared.

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Part 2: Prepare serial dilutions for AX

4. Start with the AX solutions:

   • A(NO_3)_2 as the source of A^{2+}
   • K_2X as the source of X^{2-}

5. Prepare a series of diluted solutions from the stock solutions.

   • Use the serial dilution method your instructor demonstrated.
   • Write down exactly:
     • volume of stock used
     • volume of water added
     • total volume
     • calculated new concentration

6. Keep track of the concentration of each diluted A^{2+} solution and each diluted X^{2-} solution you make.

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Part 3: Test AX for precipitate formation

7. Choose one A^{2+} solution and one X^{2-} solution to mix for Trial 1.

8. Measure the chosen volumes and combine them in the same well or test tube.

9. Immediately observe the mixture for precipitate formation.

   • Record yes/no
   • If useful, also note cloudy, slightly cloudy, or obvious solid

10. For that trial, record:

• starting concentration of A^{2+}
• starting concentration of X^{2-}
• volumes mixed
• concentration of each ion at the instant of mixing
• Q_{sp} = [A^{2+}][X^{2-}]
• whether AX precipitated

11. Repeat with different concentration combinations until you find the region where AX changes from:

• no precipitate
  to
• precipitate forms

12. The best estimate for K_{sp} of AX comes from the trial that is closest to saturation / first visible precipitate, because that is where Q_{sp} is about equal to K_{sp}. The slide asks how Q_{sp} is related to K_{sp}, and that relationship is the whole basis of the lab.

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Part 4: Prepare serial dilutions for BY_2

13. Start with the BY_2 solutions:

• 0.332 M B(NO_3)_2
• 0.50 M KY

14. Prepare serial dilutions for the B^{2+} and/or Y^{-} solutions as directed by your instructor.

15. Record exactly how each dilution was made:

• stock volume
• water volume
• total volume
• resulting concentration

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Part 5: Test BY_2 for precipitate formation

16. Mix one B^{2+} solution with one Y^{-} solution for each trial.

17. Observe whether a precipitate forms.

18. For each trial, record:

• starting concentration of B^{2+}
• starting concentration of Y^{-}
• volumes mixed
• concentration at the instant of mixing
• Q_{sp} = [B^{2+}][Y^{-}]^2
• whether BY_2 precipitated

19. Repeat until you find the concentration range where the mixture changes from no precipitate to precipitate.

20. Use the trial nearest saturation / first precipitate to estimate K_{sp} for BY_2, so Q_{sp} \approx K_{sp} at that point.

---

What you are collecting during the lab

From the slides, for each trial you need:

• starting ion concentrations
• reaction mixture information
• Q_{sp}
• whether precipitate formed

And from the report instructions, you also need to be specific about:

• how each dilution was prepared
• how the reaction mixture was prepared
• example calculations for each reaction

---

Blank data tables

Table 1. AX serial dilution preparation

Dilution ID	Solution made	Stock concentration (M)	Volume of stock used (mL or drops)	Volume of water added (mL or drops)	Total volume (mL or drops)	New concentration (M)
1	A^{2+} or X^{2-}
2	A^{2+} or X^{2-}
3	A^{2+} or X^{2-}
4	A^{2+} or X^{2-}
5	A^{2+} or X^{2-}

Table 2. AX reaction trials

Trial	[A^{2+}] starting solution (M)	[X^{2-}] starting solution (M)	Volume of A^{2+} mixed	Volume of X^{2-} mixed	Total mixed volume	[A^{2+}] at mixing (M)	[X^{2-}] at mixing (M)	Q_{sp} = [A^{2+}][X^{2-}]	Precipitate?	Notes
1
2
3
4
5
6

Table 3. BY_2 serial dilution preparation

Dilution ID	Solution made	Stock concentration (M)	Volume of stock used (mL or drops)	Volume of water added (mL or drops)	Total volume (mL or drops)	New concentration (M)
1	B^{2+} or Y^{-}
2	B^{2+} or Y^{-}
3	B^{2+} or Y^{-}
4	B^{2+} or Y^{-}
5	B^{2+} or Y^{-}

Table 4. BY_2 reaction trials

Trial	[B^{2+}] starting solution (M)	[Y^{-}] starting solution (M)	Volume of B^{2+} mixed	Volume of Y^{-} mixed	Total mixed volume	[B^{2+}] at mixing (M)	[Y^{-}] at mixing (M)	Q_{sp} = [B^{2+}][Y^{-}]^2	Precipitate?	Notes
1
2
3
4
5
6

Table 5. Final K_{sp} estimate summary

Salt	Trial chosen as closest to saturation	Evidence used	Q_{sp} for that trial	Estimated K_{sp}
AX
BY_2

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Quick note on what you’ll probably see

If Q_{sp} > K_{sp}, a precipitate should form.
If Q_{sp} < K_{sp}, no precipitate should form.
If Q_{sp} \approx K_{sp}, the solution is right at saturation and that trial is the one you use to estimate K_{sp}. This matches the concepts your slide asks you to think about.

If you want, next I can turn this into:

1. a clean methods section you can use in your lab report, or
2. a filled-in sample calculation template for AX and BY_2.

Yes — I made the PDF and it’s ready to print.

I fixed the formatting so the headers display correctly and saved it as Ksp Lab Blank Data Tables.pdf.

If you want, I can also make a Word version next.

Here’s a simple setup breakdown based on the lab slides you shared. The experiment is to make serial dilutions of the ion solutions, then mix pairs of solutions and check whether a precipitate forms so you can compare Q_{sp} to K_{sp}. The slides show the stock solutions for AX as 0.50 M A(NO_3)_2 and 0.50 M K_2X, and for BY_2 as 0.332 M B(NO_3)_2 and 0.50 M KY.

Materials

• 0.50 M A(NO_3)_2
• 0.50 M K_2X
• 0.332 M B(NO_3)_2
• 0.50 M KY
• Distilled water
• Dropper pipets or transfer pipets
• Small test tubes, spot plate, or well plate
• Beakers or cups for holding solutions
• Labels or marker
• Your blank data table sheet
• Calculator
• Safety goggles, gloves, lab coat if required

How to set up the experiment

1. Organize your workspace

Put on goggles first. Clear your area and label sections for:

• AX dilutions
• AX trials
• BY_2 dilutions
• BY_2 trials

Keep the four stock solutions separate so you do not mix droppers between chemicals.

2. Set out the stock solutions

Place the four stock solutions in front of you:

• A(NO_3)_2
• K_2X
• B(NO_3)_2
• KY

These are your starting chemicals for the two salts you are testing.

3. Prepare dilution containers

Set up several labeled tubes or wells for diluted solutions. You will need separate dilution sets for:

• A^{2+} and/or X^{2-} for AX
• B^{2+} and/or Y^{-} for BY_2

Label them clearly, like:

• A1, A2, A3...
• X1, X2, X3...
• B1, B2, B3...
• Y1, Y2, Y3...

4. Make serial dilutions

Using stock solution plus water, prepare weaker concentrations step by step.
For each dilution, write down:

• which solution you made
• stock concentration
• volume of stock used
• volume of water added
• total volume
• new concentration

The report slide says to be specific about how each dilution was prepared, so record every step as you do it.

5. Set up reaction trials for AX

Choose one diluted A^{2+} solution and one diluted X^{2-} solution. Mix them in one clean well or test tube.

For each AX trial, record:

• starting [A^{2+}]
• starting [X^{2-}]
• amount of each solution mixed
• total volume
• concentration of each ion at mixing
• Q_{sp} = [A^{2+}][X^{2-}]
• whether a precipitate formed

6. Set up reaction trials for BY_2

Choose one diluted B^{2+} solution and one diluted Y^{-} solution. Mix them in a clean well or tube.

For each BY_2 trial, record:

• starting [B^{2+}]
• starting [Y^{-}]
• amount of each solution mixed
• total volume
• concentration of each ion at mixing
• Q_{sp} = [B^{2+}][Y^{-}]^2
• whether a precipitate formed

7. Watch carefully for precipitate formation

After each mixture, look for:

• clear solution = no precipitate
• cloudy solution or solid = precipitate formed

The point of the experiment is to find the trial near the boundary between no precipitate and precipitate, because that is where Q_{sp} is about equal to K_{sp}.

Simple lab flow

1. Gather materials
2. Label tubes/wells
3. Make serial dilutions
4. Mix one pair for a trial
5. Observe precipitate or no precipitate
6. Record concentrations and volumes
7. Calculate Q_{sp}
8. Repeat with new concentrations
9. Find the trial closest to saturation

Important tips

• Use a separate dropper for each solution if possible.
• Keep units consistent for all volumes.
• Label everything before you start mixing.
• Record data immediately, not later.
• If the lab uses drops, count carefully and use the same dropper style throughout.
• If a mixture turns cloudy even slightly, note that in the observations.

If you want, I can next turn this into a super short numbered methods section you can bring to lab, like a checklist.

Yes — but one important thing first: the lab pages you linked only give placeholder chemical names, not real element names. They show A(NO_3)_2, K_2X, B(NO_3)_2, and KY, with stock concentrations of 0.50 M for A(NO_3)_2, 0.50 M for K_2X, 0.332 M for B(NO_3)_2, and 0.50 M for KY. I don’t see actual identities like calcium nitrate or silver nitrate anywhere in the linked lab pages, so I shouldn’t invent them.

So here’s a specific checklist using the names the lab actually gives.

Ksp lab setup checklist

Materials

• 0.50 M A(NO_3)_2
• 0.50 M K_2X
• 0.332 M B(NO_3)_2
• 0.50 M KY
• Distilled water
• Well plate or spot plate
• 4 transfer pipets or droppers minimum, ideally one per solution
• Extra pipet/dropper for distilled water
• Small beakers or cups for each solution
• Marker for labeling
• Printed blank data table
• Calculator
• Goggles and gloves

The procedure in the handout is to combine the AX pair first, then the BY_2 pair, then repeat at diluted concentrations and check for precipitate formation.

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Well plate setup

Use one well plate and divide it into sections.

Label the plate like this:

Top rows: AX

• Row A = AX serial dilutions
• Row B = AX reaction trials

Bottom rows: BY_2

• Row C = BY_2 serial dilutions
• Row D = BY_2 reaction trials

If your plate has many wells, label reaction wells like:

• B1, B2, B3, B4, B5, B6 for AX trials
• D1, D2, D3, D4, D5, D6 for BY_2 trials

If you are using a smaller plate, just number the wells on paper and keep a matching chart.

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Set up the solutions

1. Put stock solutions in separate labeled containers

Label four containers:

• A(NO_3)_2, 0.50 M
• K_2X, 0.50 M
• B(NO_3)_2, 0.332 M
• KY, 0.50 M

2. Assign one pipet to each solution

Do not use the same dropper for different chemicals.
That prevents contamination.

Suggested:

• Pipet 1 = A(NO_3)_2
• Pipet 2 = K_2X
• Pipet 3 = B(NO_3)_2
• Pipet 4 = KY
• Pipet 5 = water

---

AX setup checklist

3. Prepare AX dilution wells

In Row A, make your dilution set for the AX reactants:

• diluted A^{2+} solutions from 0.50 M A(NO_3)_2
• diluted X^{2-} solutions from 0.50 M K_2X

For each dilution, record:

• stock concentration
• drops or mL of stock used
• drops or mL of water added
• total volume
• new concentration

The slides say each AX trial needs the starting [A^{2+}] and [X^{2-}], then Q_{sp} = [A^{2+}][X^{2-}], and whether AX precipitated.

4. Set up AX reaction wells

Use Row B for actual AX mixtures.

For each AX trial:

1. Pick one A^{2+} concentration.
2. Pick one X^{2-} concentration.
3. Add both to one clean well.
4. Mix gently by tapping or swirling carefully.
5. Observe immediately for precipitate/cloudiness.
6. Record yes/no for precipitate.

AX reaction label example

• B1 = AX trial 1
• B2 = AX trial 2
• B3 = AX trial 3
• B4 = AX trial 4
• B5 = AX trial 5
• B6 = AX trial 6

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BY_2 setup checklist

5. Prepare BY_2 dilution wells

In Row C, make dilution sets for:

• diluted B^{2+} solutions from 0.332 M B(NO_3)_2
• diluted Y^{-} solutions from 0.50 M KY

For each dilution, record:

• stock concentration
• stock volume
• water volume
• total volume
• new concentration

The slides say each BY_2 trial needs the starting [B^{2+}] and [Y^-], then Q_{sp} = [B^{2+}][Y^-]^2, and whether precipitate formed.

6. Set up BY_2 reaction wells

Use Row D for actual BY_2 mixtures.

For each trial:

1. Pick one B^{2+} concentration.
2. Pick one Y^{-} concentration.
3. Add both to one clean well.
4. Mix gently.
5. Look for cloudiness or solid.
6. Record yes/no for precipitate.

BY_2 reaction label example

• D1 = BY_2 trial 1
• D2 = BY_2 trial 2
• D3 = BY_2 trial 3
• D4 = BY_2 trial 4
• D5 = BY_2 trial 5
• D6 = BY_2 trial 6

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What to record for every reaction well

AX wells

Record:

• trial number
• starting [A^{2+}]
• starting [X^{2-}]
• volume of A^{2+} added
• volume of X^{2-} added
• total volume
• [A^{2+}] at mixing
• [X^{2-}] at mixing
• Q_{sp} = [A^{2+}][X^{2-}]
• precipitate yes/no

BY_2 wells

Record:

• trial number
• starting [B^{2+}]
• starting [Y^-]
• volume of B^{2+} added
• volume of Y^- added
• total volume
• [B^{2+}] at mixing
• [Y^-] at mixing
• Q_{sp} = [B^{2+}][Y^-]^2
• precipitate yes/no

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Simple working order in lab

1. Put on goggles.
2. Label the well plate rows for AX and BY_2.
3. Set out the four stock solutions.
4. Assign one dropper to each solution.
5. Make AX dilutions.
6. Run AX reaction trials.
7. Make BY_2 dilutions.
8. Run BY_2 reaction trials.
9. Record precipitate observations right away.
10. Calculate Q_{sp} for each trial.
11. Find the trial closest to saturation, where Q_{sp} is about equal to K_{sp}. The lab specifically asks you to think about the relationship between Q_{sp} and K_{sp}.

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Important note about amounts

I still do not see exact required mixing volumes or exact numbers of drops in the linked lab pages. So I can give you the setup structure, but not a truthful “add exactly 5 drops of this and 5 drops of that” unless that is on a page you haven’t shown yet. If you send that page or the PowerPoint slide with the well-plate directions, I can turn this into a fully exact checklist with the real drop counts.

If you want, next I can make you:

1. a one-page lab bench checklist, or
2. a well plate map diagram showing exactly where to put each trial.

From the example data, the unknown K_{sp} for AX is about 8.5 \times 10^{-5}.

Here’s why. In the example table for AX:

• A4: no, actually Yes precipitate, with Q_{sp} = 1.0 \times 10^{-4}
• A5: No precipitate, with Q_{sp} = 6.97 \times 10^{-5}

That means the real K_{sp} must be between those two values:

6.97 \times 10^{-5} < K_{sp} < 1.0 \times 10^{-4}

The example report says they averaged those boundary trials to estimate K_{sp}.

So:

K_{sp} \approx \frac{1.0 \times 10^{-4} + 6.97 \times 10^{-5}}{2}
= 8.485 \times 10^{-5}

Rounded:

K_{sp} \approx 8.49 \times 10^{-5}

The abstract on page 2 gives essentially the same result, written as 8.42 \times 10^{-5} for AX, which is close enough that the small difference is probably from rounding or teacher edits.

For your wording:

• unknown K_{sp} for AX: about 8.4 \times 10^{-5}
• if you mean the identity of A and X, this example page does not reveal the actual chemicals — it still uses placeholders A and X, so I can’t truthfully name the ions from this file alone.

If you want, I can also do the same breakdown for BY_2 and show exactly how the boundary-trial logic works.

For BY_2, the example’s estimated unknown K_{sp} is about 4.4 \times 10^{-6}. That value is stated directly in the example abstract and again in the later results/discussion area.

The logic is the same as AX: find the boundary trials where one trial is just below precipitation and the next is just above it, then estimate K_{sp} from the Q_{sp} values near that boundary. The example explicitly says they used the average of boundary trials for AX, and the BY_2 section on page 5 points to B4 and B5 as the key boundary region, along with concentrations at mixing and the final K_{sp} value.

From page 5, the listed mixing concentrations are:

• [B^{2+}] = 0.0125 M
• [Y^-] = 0.0188 M

Using the lab expression for this salt,

Q_{sp} = [B^{2+}][Y^-]^2

so

Q_{sp} = (0.0125)(0.0188)^2 \approx 4.42 \times 10^{-6}

That matches the reported example value:

K_{sp} \approx 4.4 \times 10^{-6}

So your two example unknowns are:

• AX: K_{sp} \approx 8.4 \times 10^{-5}
• BY_2: K_{sp} \approx 4.4 \times 10^{-6}

If you want, I can next write a very short conclusion paragraph using those values in beginner-friendly lab-report wording.

Your Part 2 is off because the Q_{sp} expression is being used wrong.

For BY_2, the lab slide says:

Q_{sp} = [B^{2+}][Y^-]^2

—not just [B^{2+}][Y^-].

So for your first Part 2 trial, using the numbers you wrote:

• [B^{2+}]_{mix} = 0.083
• [Y^-]_{mix} = 0.125

Then:

Q_{sp} = (0.083)(0.125)^2

Q_{sp} = (0.083)(0.015625) \approx 0.00130

Q_{sp} \approx 1.30 \times 10^{-3}

That is not 1.0 \times 10^{-2}. So your first issue is a calculation/setup mistake.

For your second trial:

• [B^{2+}]_{mix} = 0.0996
• [Y^-]_{mix} = 0.15

Q_{sp} = (0.0996)(0.15)^2

Q_{sp} = (0.0996)(0.0225) \approx 0.00224

Q_{sp} \approx 2.24 \times 10^{-3}

So that is also not 1.25 \times 10^{-2}.

Why your teacher said it should be around 10^{-6}

Because the true K_{sp} for the example BY_2 system is around 4.4 \times 10^{-6}, and the boundary trial near first precipitation should give a Q_{sp} in that same ballpark.

Your values are around 10^{-3}, which is about 1000 times too large. That usually means one of these happened:

1. You used the stock concentrations instead of the actual diluted concentrations.
   This is the most likely problem.

2. Your “at mixing” concentrations were not diluted correctly.
   If you mix equal volumes, the concentration at mixing should be half of the initial solution concentration.

3. You may have copied the wrong initial concentrations from the serial dilution step.

4. The ion concentration for Y may have been treated incorrectly.
   But since KY gives one Y^-, that part is probably fine if the chemical is written that way.

Another red flag in your data

You wrote for Trial 1:

• initial [B(NO_3)_2] = 0.166
• initial [KY] = 0.25
• at mixing [B^{2+}] = 0.083
• at mixing [Y^-] = 0.125

That suggests you mixed equal volumes, because each concentration got cut in half. That part is fine.

But if those are really your concentrations, then your experiment is nowhere near the 10^{-6} range. Even the corrected Q_{sp} is still:

1.30 \times 10^{-3}

which is much larger than 10^{-6}.

So the real issue is probably earlier: your serial dilutions were not diluted enough, or the concentrations copied into Part 2 are not the actual final diluted trial concentrations.

Compare to the example

The example BY_2 trial near the correct answer used much smaller mixing concentrations:

• [B^{2+}] = 0.0125
• [Y^-] = 0.0188

Then:

Q_{sp} = (0.0125)(0.0188)^2 \approx 4.4 \times 10^{-6}

Your concentrations:

• 0.083 and 0.125

are much bigger than:

• 0.0125 and 0.0188

So naturally your Q_{sp} comes out way bigger.

Bottom line

Your Part 2 is way off because:

• you likely calculated Q_{sp} incorrectly
• and/or you used concentrations that are too large, probably from the wrong serial dilution level

Corrected Part 2 values from what you posted

Trial 1

Q_{sp} = (0.083)(0.125)^2 = 1.30 \times 10^{-3}

Trial 3

Q_{sp} = (0.0996)(0.15)^2 = 2.24 \times 10^{-3}

Still far above 10^{-6}.

If you want, I can take your Part 2 numbers and help you rebuild the table correctly step by step to figure out what concentration should have been used.

If your teacher said to treat it as 1:1 for this class setup, then use:

Q_{sp} = [B^{2+}][Y^-]

With that rule, your numbers become:

Trial 1

Q_{sp} = (0.083)(0.125) = 0.010375 \approx 1.04 \times 10^{-2}

Trial 3

Q_{sp} = (0.0996)(0.15) = 0.01494 \approx 1.49 \times 10^{-2}

So your table values near 10^{-2} are actually consistent with that 1:1 assumption.

So why is your data still way off from 10^{-6}?

Then the issue is not the squaring. The real problem is that your concentrations are way too large.

If the expected Q is around 10^{-6}, then the numbers being multiplied should be much smaller.

For example:

• 0.083 \times 0.125 \approx 10^{-2}
• but something like 0.001 \times 0.001 \approx 10^{-6}

So the problem is almost certainly one of these:

1. You copied the wrong concentrations into the table

This is the most likely.

Your listed “initial” concentrations are:

• 0.166
• 0.25

Those are still very concentrated. They do not look like the final tiny serial-dilution values you’d expect for a 10^{-6}-ish result.

2. You used an early dilution instead of a later dilution

If you grabbed one of the first dilution steps, the concentrations would still be large, and Q would come out too big.

3. Your serial dilution math is wrong

If the dilution factor was supposed to continue across several wells and you only halved once, your concentrations would stay much too high.

4. The teacher may be expecting the concentration after more dilution than just mixing

For example, if you diluted in the well plate first and then mixed again, you may need one more dilution step in the concentration calculation.

Quick reality check

To get Q \approx 10^{-6} with 1:1 math:

If the two ions are about equal, then each one would need to be around:

\sqrt{10^{-6}} = 10^{-3}

So each mixed concentration should be around 0.001 M, not:

• 0.083 M
• 0.125 M

Your concentrations are about 100 times too big, and when multiplied that makes Q about 10,000 times too big.

That’s why you’re landing near 10^{-2} instead of 10^{-6}.

Bottom line

If the class is using 1:1:

• your Q calculation is fine
• your concentrations are the problem

So the real error is likely:

• wrong dilution values copied
• wrong dilution step used
• missing another dilution factor

What to check on your paper

Look back at:

1. the actual serial dilution wells
2. which dilution numbers were used in the reaction
3. whether the “initial” values in your table are stock, diluted, or post-mix
4. whether there was an additional dilution when combining wells

If you want, send me the actual serial dilution numbers or a photo of your Part 2 setup, and I’ll pinpoint exactly where the concentration error happened.

Because with your numbers, Q is much bigger than the cutoff, so precipitation makes sense.

If your class is treating it as 1:1, then for Trial 3:

Q = [B^{2+}][Y^-] = (0.0996)(0.15) = 1.49 \times 10^{-2}

That is a pretty large ion product. If the threshold for precipitation is much smaller, then once you mix them, the solution is supersaturated, so a precipitate should form.

So the precipitate itself is not the weird part. The weird part is this:

• your data shows concentrations high enough to give Q \sim 10^{-2}
• but your teacher says the answer should be around 10^{-6}

Those two things do not match. That means one of these is true:

Option 1: Your recorded concentrations are wrong

This is most likely.

If the concentrations written in the table are too high, then your calculated Q will also be too high, even if the observed precipitate is real.

Option 2: The precipitate observation is correct, but this was not the boundary trial

A trial can absolutely precipitate at 10^{-2}. That just means it is well above the precipitation threshold.
So if your teacher wanted the trial closest to K_{sp}, this trial may simply be too concentrated to use for the final estimate.

Option 3: You are mixing up “a trial that precipitated” with “the trial used to estimate K_{sp}”

Those are not always the same.

To estimate K_{sp}, you usually want the trial closest to the change point:

• one trial with no precipitate
• one nearby trial with precipitate

Then the true value lies between those two.

So yes, you can definitely get a precipitate with your numbers. In fact, your numbers strongly predict one.

The key idea

A precipitate forms when:

Q > K_{sp}

So if your calculated Q is around 10^{-2}, then precipitation is exactly what you’d expect if the true K_{sp} is smaller than that.

Your teacher’s “around 10^{-6}” comment probably means:

• the correct boundary-region trial should have had Q near 10^{-6}
• not that every precipitating trial has to be 10^{-6}

So the answer

You got a precipitate because your mixture, as recorded, was concentrated enough that Q came out very large. That would push the system past saturation and form solid.

What’s off is not “why did it precipitate?”
What’s off is “why are these the concentrations being used for the final K_{sp} estimate?”

If you want, I can help you figure out which of your Part 2 trials should actually be used to estimate K_{sp} from the precipitate/no-precipitate pattern.