13.4.2 Conditions for Spontaneity

• What does Gibbs Free Energy predict about a process under constant pressure and temperature conditions?

  Spontaneity
• The equation for Gibbs Free Energy is G = H - TS
• A negative $ΔG$ indicates a spontaneous process.
• What are the three parameters related to Gibbs Free Energy in the equation?

  Enthalpy, entropy, temperature
• If $ΔH$ is negative and $ΔS$ is positive, the reaction is always spontaneous
• Match the conditions with their effect on spontaneity:

  $ΔH < 0$ and ΔS < 0</latex> ↔️ Spontaneous at low temperatures

  $ΔH > 0$ and $ΔS > 0$ ↔️ Spontaneous at high temperatures

  $ΔH > 0$ and $ΔS < 0$ ↔️ Non-spontaneous at all temperatures
• What does a negative $ΔG$ value indicate about a process?


  Spontaneity
• A spontaneous reaction occurs without continuous external input of energy
• If $ΔG$ is equal to zero, the reaction is at equilibrium.
• Which three parameters influence the spontaneity of a reaction?

  Enthalpy, entropy, temperature
• Arrange the following conditions based on their effect on spontaneity:

  1️⃣ $ΔH < 0$ and $ΔS > 0$

  2️⃣ $ΔH < 0$ and $ΔS < 0$

  3️⃣ $ΔH > 0$ and $ΔS > 0$

  4️⃣ $ΔH > 0$ and $ΔS < 0$
• A reaction is spontaneous if $ΔG > 0$.


  False
• What is the equation for Gibbs Free Energy (G)?

  $G =$$H - TS$
• A negative $ΔG$ indicates a spontaneous process
• If $ΔH$ is negative and $ΔS$ is positive, the reaction is spontaneous at all temperatures.
• Under what temperature conditions is a reaction with $ΔH < 0$ and $ΔS < 0$ spontaneous?


  Low temperatures
• If $ΔH$ is positive and $ΔS$ is negative, the reaction is always non-spontaneous
• Match the signs of $ΔH$ and $ΔS$ with their effect on overall spontaneity:


  $ΔH < 0$, $ΔS > 0$ ↔️ Always Spontaneous

  $ΔH < 0$, $ΔS < 0$ ↔️ Spontaneous at low temperatures

  $ΔH > 0$, $ΔS > 0$ ↔️ Spontaneous at high temperatures

  $ΔH > 0$, $ΔS < 0$ ↔️ Always Non-spontaneous
• Spontaneity refers to a reaction proceeding without external energy input once initiated.
• What is the modified Gibbs Free Energy equation for reactions with enthalpy and entropy changes?

  $ΔG =$$ΔH - TΔS$
• A $ΔG$ less than zero indicates a spontaneous reaction
• Spontaneity is determined by the Gibbs Free Energy change at constant pressure and temperature.
• For the reaction $H₂(g) +$$O₂(g) → 2H₂O(l)$, what is the value of $ΔG$ at 298 K if $ΔH =$$- 572$ kJ and $ΔS =$$- 326$ J/K?


  $- 474.7$ kJ
• A reaction is spontaneous at all temperatures if $ΔH$ is negative and $ΔS$ is positive
• Which reaction is spontaneous at low temperatures because ΔH</latex> is negative and $ΔS$ is negative?


  $N₂(g) +$$3H₂(g) → 2NH₃(g)$
• Gibbs Free Energy is used to determine the spontaneity of a process under constant pressure and temperature.
• A negative $ΔG$ indicates a spontaneous process
• Summarize the conditions for overall spontaneity based on the signs of $ΔH$ and $ΔS$:


  1️⃣ $ΔH < 0$, $ΔS > 0$: Always Spontaneous

  2️⃣ $ΔH < 0$, $ΔS < 0$: Spontaneous at low temperatures

  3️⃣ $ΔH > 0$, $ΔS > 0$: Spontaneous at high temperatures

  4️⃣ $ΔH > 0$, $ΔS < 0$: Always Non-spontaneous
• The spontaneity of a reaction depends on the interplay between $ΔH$ and $ΔS$ as defined by the Gibbs Free Energy equation.
• What is spontaneity in chemical reactions defined as?

  Proceeding without external energy input
• The Gibbs Free Energy equation is ΔG
• A negative ΔG indicates a spontaneous reaction.
• Under what conditions is a reaction always spontaneous?

  Negative ΔH and positive ΔS
• Spontaneity depends on the interplay between enthalpy change and entropy change, combined through the Gibbs Free Energy equation
• What does a positive ΔG indicate?

  Non-spontaneous reaction
• A reaction is spontaneous if ΔG < 0.
• For the reaction $H₂(g) +$$O₂(g) → 2H₂O(l)$, ΔH is -572 kJ.
• Calculate the ΔG for the reaction $H₂(g) +$$O₂(g) → 2H₂O(l)$ at 298 K given ΔH = -572 kJ and ΔS = -326 J/K.


  -474.7 kJ
• A negative ΔG always indicates a spontaneous reaction regardless of temperature.

  False
• What combination of ΔH and ΔS results in spontaneity at all temperatures?

  Negative ΔH and positive ΔS