All topicsA gas X reacts reversibly and independently to form two different gases, Y and Z: X(g) ⇌ Y(g) KY X(g) ⇌ Z(g) K2020 national · question 368%A mixture containing CO(g), H₂O(g), CO₂(g), and H₂(g) is allowed to reach equilibrium at 120 °C in a container2024 national · question 359%At high temperatures, solid calcium carbonate (M = 100.09) is in equilibrium with solid calcium oxide and carb2025 national · question 3414%
Equilibrium
This is block 6 of 10, questions 31–36 on both the local section exam and national Part I. Across the 42 national questions where ACS published item statistics, qualifiers answered 43% correctly, which makes it the second hardest of the 10.
What it covers
equilibrium constantsLe ChatelierICE tablesKspacid-base equilibriabufferstitration curvescomplex ions
Where qualifiers lose points
% who got it rightThese are the equilibrium questions the fewest national qualifiers answered correctly. If you can do these, the block is not your problem.
Every question is from a published past exam and carries its source. Practice adapts to what you miss, and anything you get wrong comes back on a spaced schedule. No account needed. See the other nine blocks.