AAMC FL 4 questions and answers with solutions 2025

Limestone does NOT decompose when heated to 900 K because, at 900 K, ΔH is: A. Positive and less than TΔS B. Positive and greater than TΔS C. Negative and less than TΔS D. Negative and greater than TΔS - ANSWER B. The reaction does not occur (is not spontaneous). This indicates that the ΔG =ΔH-TΔS >0. From inspection of the reaction, it can be concluded that ΔS>0. Consequently, ΔH>TΔS explains why the reaction does not occur When limestone is heated during Step 1, an equilibrium is established. Which of the following expressions is the equilibrium constant for the decomposition of limestone? A. [CaO] B. [CaCO3] C. [CO2] D. [CaO] x [CaCO3] - ANSWER C. From the law of mass action, an equilibrium constant expression involves a ration of products to reactants with exponents determined from the stoichiometry of the reaction. Furthermore, solids are excluded from equilibrium constant expressions. CO2 (g), as the only non-solid material in the reaction, is the only substance that appears in the equilibrium constant expression. During Reaction 2, did the oxidation state of N change? A. Yes; it changed from -3 to -4 B. Yes; it changed from 0 to +1 C. No; it remained at -3 D. No; it remained at +1 - ANSWER C. The part of the Reaction 2 that involves nitrogen is the protonation of ammonia (NH3 + H--> NH4+). Acid-base reactions doe not involve oxidation state changes. Furthermore the oxidation states of N in NH3 is -3 not 0. If all of Gas X (from Step 6) is held in a sealed chamber at STP, what will be its appropriate volume? A. 22.4 L B. 44.8 L C. 67.2 L D. 89.6 L - ANSWER A. The quantity of Gas X was given as 1 mole. One mole of gas occupies 22.4 L at STP.