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UAT-UK SPEC: C8MODULE: CHEMISTRYTOPIC ID: ARCH-C-07

Solubility Curves (g per 100 g Water), Recrystallisation Mass & Paper/TLC Chromatography Rf

Master Solubility Curves (g per 100 g Water), Recrystallisation Mass & Paper/TLC Chromatography Rf on the ESAT Chemistry paper. Traditional classroom derivations waste valuable seconds. Using the 2-step Sub-90 invariant elimination method compresses solve time to 40s, saving +105s per question.

Standard Classroom Time
145s
Textbook multi-line derivations bleed exam clock
Sub-90 Target Pace
40s
Comfortably below the 88.8s per-question limit
Time Saved for Review
+105s
Banks clock buffer across 27 questions

2-Step Sub-90 Shortcut Formula

How to eliminate intermediate algebra and solve under 45 seconds.

Launch Interactive Lesson
STEP 1 • SETUP INVARIANT (LINE 1)10–15s
Line 1 (ΔS\Delta S per 100 g100\text{ g}): ΔS=110−30=80 g\Delta S = 110 - 30 = 80\text{ g}.

Establish the structural invariant and eliminate impossible options immediately.

STEP 2 • FAST SOLVE (LINE 2)15–25s
Line 2 (Scale to 50 g50\text{ g} Water): 50100×80=40 g\frac{50}{100} \times 80 = 40\text{ g} (20s).

Evaluate the simplified expression using integer factoring or unit elimination.

Distractor Trap Forensics

The predictable cognitive traps engineered by examiners into the wrong options.

TRAP #1subsystem_isolation_trap

Scaling solubility difference (S(hot) - S(cold)) by total saturated SOLUTION mass instead of pure WATER solvent mass

If solubility at T(hot) is 80 g / 100 g water, 100 g of saturated *solution* contains 100*(100/180) g of water, not 100 g of water!

Sub-90 Fix: Test invariants before expanding equations.
TRAP #2intermediate_stop_trap

Outputting the mass remaining dissolved at T(cold) instead of the mass of crystals precipitated (m(hot) - m(cold))

Stopping at final dissolved mass without subtracting from initial dissolved mass.

Sub-90 Fix: Test invariants before expanding equations.
TRAP #3fence_post_or_domain_trap

Measuring Rf distance from the bottom edge of the chromatography paper instead of the pencil baseline origin

Failing to subtract the baseline offset from spot and solvent front heights.

Sub-90 Fix: Test invariants before expanding equations.

Try 1 Timed Question: Solubility Curves (g per 100 g Water), Recrystallisation Mass & Paper/TLC Chromatography Rf

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Full Lesson All 15 Questions (ARCH-C-07)
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ARCH-C-07: Solubility Curves (g per 100 g Water), Recrystallisation Mass & Paper/TLC Chromatography Rf (Sample)Chemistry
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SUB-90 ZONE (<40S)
0.0s40s Sub-9090s ESAT Budget150s Classroom
Question 1 of 1ARCH-C-07 (6-Card Lesson)Format: Standard 5-Option
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Question 1 of 1 • 90s Target

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