The question
Name: ______________________ Date: ____________ Hydrogen iodide equilibrium from particle diagrams (10 points)
Particle view
Two snapshots of one container
Key: H2I2HI
Hydrogen and iodine react in a sealed 1.0 L container at constant temperature: H2(g) + I2(g) ⇌ 2 HI(g). Each molecule drawn represents 0.010 mol.
(a) (i) Identify evidence from the diagrams that the system is at equilibrium. (ii) A student says that because nothing changes between t1 and t2, the reactions have stopped. Explain why the student is incorrect. [2 points]
(b) Calculate the value of Kc. [2 points]
(c) At constant temperature, the volume of the container is suddenly reduced to 0.50 L. (i) Determine whether the amount of HI changes as the system responds. Justify your answer by comparing Q with K. (ii) Draw a particle diagram of the 0.50 L container once equilibrium is re-established, using the same key. [3 points]
(d) Starting again from the original 1.0 L equilibrium mixture, 4 more H2 molecules (0.040 mol) are injected at constant temperature. (i) Calculate Q immediately after the injection. (ii) Justify the direction of the net reaction that follows. [2 points]
(e) Explain why, after the system in part (d) returns to equilibrium, the value of Kc is still 9.0. [1 point]