ARCH-C-09: Reaction Rate Tangent Gradients, Volume-Time Plateau Curves & Catalyst Foils

Full 15-Q Timed Drill

Step 1 of 6 • The Core Idea

ARCH-C-09: Why the 130s Classroom Method Fails Under the 90s Clock

Standard Classroom Method (Too Slow)~130s (Blows 90s Clock)

The instantaneous rate of reaction at

t = 0\text{ s}

is the gradient of the tangent to the volume-time curve at

t = 0\text{ s}

\text{Rate} = \frac{\Delta V}{\Delta t} = \frac{50 - 0}{20 - 0} = 2.5\text{ cm}^3\text{ s}^{-1}

(~80s).

The Fast ShortcutTarget: 35s (Saves 95s)

Line 1 (Tangent Gradient):

\text{Rate} = \frac{\Delta V}{\Delta t}

.
Line 2 (Divide):

\frac{50}{20} = 2.5\text{ cm}^3\text{ s}^{-1}

(15s).

Where Students Lose Time: In 10 past UAT-UK questions (4.44% of Chemistry), candidates lose 95s by a catalyst provides an alternative pathway with lower e_a, increasing initial gradient without changing δh or final yield. Instead, apply C10 with Maths 1 skill M4.14.

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