75-Archetype SyllabusChemistry • ARCH-C-10 • Spec C11

Full 6-Card Lesson 15-Question Timed Drill

UAT-UK SPEC CODE: C11 (Energetics)ASSUMED MATHS 1 PREREQUISITE: M1.2FREQUENCY: VERY HIGH

Calorimetry (q = mcΔT, ΔH = -q/n), Hess's Law Cycles & Mean Bond Enthalpies (ΣE_broken - ΣE_formed)

Deconstructed from 19 past UAT-UK questions (8.44% of all historical Chemistry papers). Students using standard A-Level classroom methods spend an average of 150s on this archetype—blowing past the 90s ESAT budget. Using the 2-line Sub-90 heuristic below compresses solve time to 40s (saving 110s per question).

Historical Frequency

19 Past Qs

8.44% of Chemistry

Classroom Trap Time

150s

+60s over 90s budget

Sub-90 Target Time

40s

Banks +110s on the clock

Dominant UI Format

5-Option A–E

Maths 1 Skill: M1.2

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-10.

Launch All 6 Active-Recall Cards

CARD 1 OF 6 • THE CLASSROOM TIME TRAP (150s)

Why Students Bleed Time:

First calculate the heat absorbed by the

100\text{ g}

of combined solution:

q = mc\Delta T = 100 \times 4.2 \times 6.0 = 2520\text{ J} = 2.52\text{ kJ}

. Next, find the moles of water formed:

n = 0.050\text{ dm}^3 \times 1.0\text{ mol dm}^{-3} = 0.050\text{ mol}

. Since the temperature rose, the reaction is exothermic (

\Delta H < 0

\Delta H = -\frac{2.52}{0.050} = -50.4\text{ kJ mol}^{-1}

(~115s).

In 19 past UAT-UK questions (8.44% of Chemistry), candidates lose 110s by reversing bendomex (breaking = endothermic +, making = exothermic -) or forgetting δh < 0 for a temperature rise. Instead, apply C11 with Maths 1 skill M1.2.

CARD 2 OF 6 • THE 2-LINE SUB-90 HEURISTIC (<40s)

**Line 1 (Total Mass

100\text{ g}

):**

q = 100 \times 4.2 \times 6.0 = 2520\text{ J} = 2.52\text{ kJ}

Line 2 (Exothermic Sign & Moles):

\Delta H = -\frac{2.52}{0.050} = -50.4\text{ kJ mol}^{-1}

(25s).

Sanity & Limit Check: Verify units/signs against sign_or_direction_flip (Calculating ΔH = sum(E_formed) - sum(E_broken) or giving positive +ΔH when temperature rises) and subsystem_isolation_trap (Using mass of solid solute (or fuel burned) as m in q = mcΔT instead of the mass of water/solution heated).

Examiner Distractor Blueprint for ARCH-C-10

FOIL #1sign_or_direction_flip

Calculating ΔH = sum(E_formed) - sum(E_broken) or giving positive +ΔH when temperature rises

Reversing BENDOMEX (Breaking = Endothermic +, Making = Exothermic -) or forgetting ΔH < 0 for a temperature rise.

Open Sign / Direction Flip Clinic

FOIL #2subsystem_isolation_trap

Using mass of solid solute (or fuel burned) as m in q = mcΔT instead of the mass of water/solution heated

Substituting reactant mass m_solid into q = m_water * c * ΔT instead of the aqueous solution mass.

Open Subsystem Isolation Trap Clinic

FOIL #3fence_post_or_domain_trap

Counting 3 C-H bonds instead of 4 in CH4, or forgetting 2 O-H bonds per H2O molecule (2 * 2 = 4 O-H bonds in 2H2O)

Under-counting bonds inside polyatomic molecules when multiplying by stoichiometric coefficients.

Open Fence-Post / Domain Trap Clinic

FOIL #4unit_or_prefix_mismatch

Failing to divide q (in J) by 1000 when converting to kJ mol⁻¹

Factor of 1000 unit mismatch between c = 4.2 J g⁻¹ °C⁻¹ and ΔH in kJ mol⁻¹.

Open Unit / Prefix Mismatch 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-10)

ARCH-C-10: Calorimetry (q = mcΔT, ΔH = -q/n), Hess's Law Cycles & Mean Bond Enthalpies (ΣE_broken - ΣE_formed) (Sample)Chemistry

00:00.0

SUB-90 ZONE (<40S)

0.0s40s Sub-9090s ESAT Budget150s Classroom

Question 1 of 1ARCH-C-10 (6-Card Lesson)Format: Standard 5-Option

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Question 1 of 1 • 90s Target

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Chemistry•ARCH-C-10•Standard 5-Option

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