75-Archetype SyllabusChemistry • ARCH-C-08 • Spec C9

Full 6-Card Lesson 15-Question Timed Drill

UAT-UK SPEC CODE: C9 (Acids, bases and salts)ASSUMED MATHS 1 PREREQUISITE: M2.6FREQUENCY: MEDIUM

Strong Acid Factor-of-10 pH Dilutions, Weak vs. Strong Acid Foils & Salt Preparation Methods

Deconstructed from 10 past UAT-UK questions (4.44% of all historical Chemistry papers). Students using standard A-Level classroom methods spend an average of 130s on this archetype—blowing past the 90s ESAT budget. Using the 2-line Sub-90 heuristic below compresses solve time to 35s (saving 95s per question).

Historical Frequency

10 Past Qs

4.44% of Chemistry

Classroom Trap Time

130s

+40s over 90s budget

Sub-90 Target Time

35s

Banks +95s on the clock

Dominant UI Format

5-Option A–E

Maths 1 Skill: M2.6

Card 1 & Card 2 Preview: The Classroom Time Trap vs. Sub-90 2-Line Rule

Excerpted from our interactive 6-Step Topic Lesson for ARCH-C-08.

Launch All 6 Active-Recall Cards

CARD 1 OF 6 • THE CLASSROOM TIME TRAP (130s)

Why Students Bleed Time:

The dilution factor is

\frac{V_{\text{final}}}{V_{\text{init}}} = \frac{1000}{10} = 100 = 10^2

. Therefore

[\text{H}^+]

decreases by a factor of

10^2

from

10^{-1}\text{ mol dm}^{-3}

10^{-3}\text{ mol dm}^{-3}

, increasing the

\text{pH}

2

units from

1.0

3.0

(~85s).

In 10 past UAT-UK questions (4.44% of Chemistry), candidates lose 95s by treating the base-10 logarithmic ph scale as a linear concentration ratio. Instead, apply C9 with Maths 1 skill M2.6.

CARD 2 OF 6 • THE 2-LINE SUB-90 HEURISTIC (<35s)

Line 1 (Dilution Power of 10):

\frac{1000}{10} = 10^2 \implies \Delta\text{pH} = +2

**Line 2 (Add to Initial

\text{pH}

):**

1.0 + 2 = 3.0

(15s).

Sanity & Limit Check: Verify units/signs against factor_of_two_or_stoichiometry_trap (Increasing pH by 2 when volume is doubled, or scaling pH linearly instead of logarithmically (ΔpH = +1 per 10x dilution)) and fence_post_or_domain_trap (Diluting a pH 5 acid by 1000x to get pH 8 (alkaline!) instead of approaching the neutral water limit pH 7).

Examiner Distractor Blueprint for ARCH-C-08

FOIL #1factor_of_two_or_stoichiometry_trap

Increasing pH by 2 when volume is doubled, or scaling pH linearly instead of logarithmically (ΔpH = +1 per 10x dilution)

Treating the base-10 logarithmic pH scale as a linear concentration ratio.

Open Factor-of-2 / Stoichiometry Clinic

FOIL #2fence_post_or_domain_trap

Diluting a pH 5 acid by 1000x to get pH 8 (alkaline!) instead of approaching the neutral water limit pH 7

Forgetting that diluting an acid with pure water (pH 7) can never push pH above 7.

Open Fence-Post / Domain Trap Clinic

FOIL #3subsystem_isolation_trap

Adding 100 cm³ of water to 10 cm³ of acid (total 110 cm³) and confusing with adding 90 cm³ of water to make 100 cm³ (10x dilution)

Confusing 'diluted TO 100 cm³' with '100 cm³ of water ADDED'.

Open Subsystem Isolation Trap Clinic

FOIL #4multi_statement_linchpin_foil

Claiming a weak acid requires a smaller volume of NaOH for neutralisation than a strong acid of equal molarity

Total neutralisation titre depends only on total moles of monoprotic acid (n = cV), not acid strength (Ka).

Open Multi-Statement Linchpin Foil Clinic

Try 1 Live Sample Question Under the 90-Second Stopwatch

Press W to open the 2-line dry-wipe scratchpad, select A–E, and lock in to reveal the Dual-View solution.

Full 6-Card Lesson Launch All 15 Questions (ARCH-C-08)

ARCH-C-08: Strong Acid Factor-of-10 pH Dilutions, Weak vs. Strong Acid Foils & Salt Preparation Methods (Sample)Chemistry

00:00.0

SUB-90 ZONE (<35S)

0.0s35s Sub-9090s ESAT Budget150s Classroom

Question 1 of 1ARCH-C-08 (6-Card Lesson)Format: Standard 5-Option

Right-click any option to cross out • Keys A–E + Enter

Question 1 of 1 • 90s Target

Ready to Start Question 1?

The question stem, diagram, and answer options are hidden behind this pre-start gate. When you click below, the question will reveal and your 90-second split stopwatch will immediately begin ticking.

Chemistry•ARCH-C-08•Standard 5-Option

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