Question detail

For the equilibrium reaction CO(g) + 2H2(g) ⇌ CH3OH(g), if P(CO) = 0.5 atm, P(H2) = 0.4 atm, and P(CH3OH) = 0.2 atm, calculate Kp. What are the units of Kp (A-level cue a266eaa6 focus)

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At a glance

MCQ

Type

practice

Style

Topic

Equilibrium constant Kp for homogeneous systems (A-level only)

Question

A. atm^-1
B. atm^2 (A-level cue a266eaa6 distractor 1)
C. atm^-2 (A-level cue a266eaa6 distractor 2)
D. none (A-level cue a266eaa6 distractor 3)

Answer

atm^-1

Explanation

The correct option is atm^-1. atm^-1 is correct because it supports the objective: Calculate Kp and determine appropriate units.. The reasoning stays within Kp and partial pressure (A-level only) and avoids drifting into a similar A-Level Chemistry idea. This version is uniquely anchored to Kp and partial pressure (A-level only). Retrieval anchor: A-level cue a266eaa6.

Common mistake

Misidentifying the Units of Kp

Students often write the equilibrium constant Kp as a dimensionless quantity, ignoring that it is expressed in terms of pressure units such as atm or bar.

Kp must be expressed with the same pressure units as the partial pressures used in the equilibrium expression, e.g. atm, bar, or kPa. When all partial pressures are in atm, Kp is given in atm⁰⁰ (dimensionless), but the convention is to state the units explicitly as atm or bar to avoid confusion. Keep the correction anchored to Kp and partial pressure (A-level only) and the objective: Calculate Kp and determine appropriate units.

Related flashcards

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A reaction at equilibrium has the following partial pressures: P(N2) = 0.5 atm, P(H2) = 1.0 atm, and P(NH3) = 2.0 atm. Calculate Kp for the reaction N2(g) + 3H2(g) ⇌ 2NH3(g). What are the units of Kp?