Ch. 17 - Chemical ThermodynamicsWorksheetSee all chapters
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Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds

Solution: Free energy and approaching equilibrium. In the reaction N2 (g) + 3H2 (g) 2NH3 (g), if the reaction mixture has too much N2 and H2 relative to NH3 (left), Q<K and NH3 forms spontaneously

Problem

The overall reaction is N2 (gas) plus 3 H2 (gas) are in equilibrium with 2 NH3 (gas).  A line graph is shown, with progress of the reaction on the X-axis and free energy (increasing) on the Y-axis (both unscaled). Initially the line is high on the free energy side, with a composition of pure N2 and H2.  The line decreases as the reaction progresses; this portion of the reaction direction is spontaneous as Q is less than K. The line then reaches a trough at the equilibrium mixture where Q equals K and delta G equals 0. To the right of the equilibrium point, the line increases somewhat, to a point of pure NH3, which has lower free energy than pure N2 and H2.  In this region, Q is greater K, and the reverse reaction is spontaneous.
Free energy and approaching equilibrium. In the reaction N2 (g) + 3H2 (g) 2NH3 (g), if the reaction mixture has too much N2 and H2 relative to NH3 (left), Q<K and NH3 forms spontaneously. If there is more NH3 in the mixture relative to the reactants N2 and H2 (right) , Q>K and the NH3 decomposes spontaneously into N2 and H2.

Why are the spontaneous processes shown sometimes said to be "downhill" in free energy?