5.3.2 Entropy changes

    Cards (46)

    • The second law of thermodynamics states that the entropy of an isolated system decreases over time.
      False
    • Entropy is a measure of the disorder or randomness
    • The main factors affecting entropy changes include temperature, pressure, and phase
    • Entropy describes the number of possible arrangements
    • Match the state with its entropy and molecular arrangement:
      Solid ↔️ Low entropy, tightly packed
      Liquid ↔️ Moderate entropy, loosely packed
      Gas ↔️ High entropy, widely dispersed
    • The second law of thermodynamics states that the entropy of an isolated system not in equilibrium will approach a maximum
    • Phase transitions from solid to gas increase entropy.

      True
    • Match the state with its entropy:
      Solid ↔️ Low entropy
      Liquid ↔️ Moderate entropy
      Gas ↔️ High entropy
    • Higher temperatures allow molecules to move more freely, increasing entropy
    • Steps to calculate entropy change (ΔS°) using standard molar entropy values:
      1️⃣ Balance the chemical equation
      2️⃣ Find S° values for reactants and products
      3️⃣ Calculate total entropy of reactants
      4️⃣ Calculate total entropy of products
      5️⃣ Apply the formula ΔS° = (Products - Reactants)
    • Consider the reaction: 2 H₂O(l) → 2 H₂(g) + O₂(g). The total entropy of the products is 467 J/K.
    • A phase change from solid to gas increases entropy.

      True
    • Why does increasing the number of gas molecules increase entropy?
      Gas molecules occupy more space
    • The second law of thermodynamics states that the entropy of an isolated system increases over time.

      True
    • What happens to entropy when heat dissipates from hot to cold areas?
      Increases
    • To calculate entropy change, the formula used is ΔS° = (Total entropy of products) - (Total entropy of reactants).
    • What is the balanced equation for the decomposition of water into hydrogen and oxygen gases?
      2 H₂O(l) → 2 H₂(g) + O₂(g)
    • The formula to calculate the change in standard entropy is ΔS°
    • What is the standard molar entropy (S°) value for H₂O(l)?
      70 J/mol·K
    • Steps to calculate entropy change for a chemical reaction
      1️⃣ Balance the chemical equation
      2️⃣ Find S° values for reactants and products
      3️⃣ Calculate total entropy of reactants
      4️⃣ Calculate total entropy of products
      5️⃣ Apply the formula: ΔS° = (Products) - (Reactants)
    • What is the standard molar entropy (S°) value for O₂(g)?
      205 J/mol·K
    • Phase changes from solid to liquid to gas increase entropy.
      True
    • Processes that increase entropy in a system
      1️⃣ Transition from solid to liquid
      2️⃣ Mixing different substances
      3️⃣ Increasing the number of gas molecules
      4️⃣ Forming more complex molecules
    • A positive entropy change leads to a decrease in Gibbs free energy.

      True
    • What is the relationship between entropy changes and Gibbs free energy?
      Entropy changes affect Gibbs free energy
    • The entropy increases when a substance transitions from a solid to a liquid.
      True
    • Entropy decreases when a substance transitions from a liquid to a gas.
      False
    • Decreasing pressure typically increases entropy
    • Entropy is a measure of the disorder or randomness
    • Systems naturally move towards states of higher entropy because there are more possible arrangements of molecules in these states.

      True
    • The change in entropy (ΔS°) for a reaction is calculated by subtracting the total entropy of products from the total entropy of reactants.
      False
    • What is the formula for calculating the change in entropy (ΔS°)?
      ΔS∘=\Delta S^\circ =∑Sproducts∘−∑Sreactants∘ \sum S^\circ_{\text{products}} - \sum S^\circ_{\text{reactants}}
    • Steps to calculate the change in entropy for a reaction
      1️⃣ Balance the chemical equation
      2️⃣ Find S° values for reactants and products
      3️⃣ Calculate total entropy of reactants
      4️⃣ Calculate total entropy of products
      5️⃣ Apply the formula ΔS° = (Total entropy of products) - (Total entropy of reactants)
    • Mixing substances typically increases entropy.
    • What does entropy measure in a system?
      Disorder or randomness
    • An isolated system does not exchange energy or matter with its surroundings.
    • Processes that increase disorder in a system also increase entropy.
      True
    • Steps to calculate entropy change using standard molar entropy values
      1️⃣ Balance the chemical equation
      2️⃣ Find S° values for reactants and products
      3️⃣ Calculate total entropy of reactants
      4️⃣ Calculate total entropy of products
      5️⃣ Apply the formula
    • What is the first step in calculating the total entropy of reactants for a chemical reaction?
      Multiply S° by stoichiometric coefficient
    • The reaction 2 H₂O(l) → 2 H₂(g) + O₂(g) is balanced.

      True
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