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Questions and Answers
What is a spontaneous reaction?
What is a spontaneous reaction?
A reaction that does occur under the given set of conditions.
Water runs downhill spontaneously.
Water runs downhill spontaneously.
True (A)
A lump of sugar dissolves in a cup of hot coffee spontaneously.
A lump of sugar dissolves in a cup of hot coffee spontaneously.
True (A)
Water freezes spontaneously below 0°C.
Water freezes spontaneously below 0°C.
Ice melts spontaneously above 0°C.
Ice melts spontaneously above 0°C.
Heat flows spontaneously from a colder object to a hotter one.
Heat flows spontaneously from a colder object to a hotter one.
Gathering of all the molecules into one is spontaneous
Gathering of all the molecules into one is spontaneous
Iron exposed to water and oxygen forms rust spontaneously.
Iron exposed to water and oxygen forms rust spontaneously.
What does the Second Law of Thermodynamics state about the universe's entropy?
What does the Second Law of Thermodynamics state about the universe's entropy?
The changes in the entropy in the universe can be negative.
The changes in the entropy in the universe can be negative.
What is entropy?
What is entropy?
Which of the following processes lead to an increase in the entropy of the system?
Which of the following processes lead to an increase in the entropy of the system?
When does positive entropy occur?
When does positive entropy occur?
When is entropy positive?
When is entropy positive?
Determine the entropy of a system when a solid melts. Is it positive or negative?
Determine the entropy of a system when a solid melts. Is it positive or negative?
Determine the entropy of a system when a Liquid freezs. Is it positive or negative?
Determine the entropy of a system when a Liquid freezs. Is it positive or negative?
Determine the entropy of a system when a vapor is converted to a solid. Is it positive or negative?
Determine the entropy of a system when a vapor is converted to a solid. Is it positive or negative?
Determine the entropy of a system when a vapor condenses to a liquid. Is it positive or negative?
Determine the entropy of a system when a vapor condenses to a liquid. Is it positive or negative?
Determine the entropy of a system when a Solid sublimes. Is it positive or negative?
Determine the entropy of a system when a Solid sublimes. Is it positive or negative?
Determine the entropy of a system for the process $2H_2(g) + O_2(g) \rightarrow 2H_2O (l)$. Is it positive or negative?
Determine the entropy of a system for the process $2H_2(g) + O_2(g) \rightarrow 2H_2O (l)$. Is it positive or negative?
Determine the entropy of a system for the process $NH_4Cl(s) \rightarrow NH_3(g) + HCl(g)$. Is it positive or negative?
Determine the entropy of a system for the process $NH_4Cl(s) \rightarrow NH_3(g) + HCl(g)$. Is it positive or negative?
Determine the entropy of a system for the process $H_2(g) + Br_2(g) \rightarrow 2HBr(g)$. Is it positive or negative?
Determine the entropy of a system for the process $H_2(g) + Br_2(g) \rightarrow 2HBr(g)$. Is it positive or negative?
Determine the entropy of a system for the process $CaCO_3(s) \rightarrow CaO(s) + CO_2(g)$. Is it positive or negative?
Determine the entropy of a system for the process $CaCO_3(s) \rightarrow CaO(s) + CO_2(g)$. Is it positive or negative?
Which physical state has the highest entropy?
Which physical state has the highest entropy?
More amount of substance result in smaller entropy.
More amount of substance result in smaller entropy.
The higher the temperature, the greater the entropy
The higher the temperature, the greater the entropy
The higher the volume/lower pressure, the greater the entropy
The higher the volume/lower pressure, the greater the entropy
Flashcards
Spontaneous Process
Spontaneous Process
A reaction that occurs under a given set of conditions.
Non-spontaneous Process
Non-spontaneous Process
A reaction that does not occur under specified conditions.
Second Law of Thermodynamics
Second Law of Thermodynamics
The universe's entropy always increases over time.
Entropy (S)
Entropy (S)
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Melting and Entropy
Melting and Entropy
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Vaporization and Entropy
Vaporization and Entropy
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Dissolving and Entropy
Dissolving and Entropy
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Heating and Entropy
Heating and Entropy
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Positive Entropy
Positive Entropy
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Negative Entropy
Negative Entropy
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Physical State and Entropy
Physical State and Entropy
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Amount of Substance and Entropy
Amount of Substance and Entropy
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Temperature and Entropy
Temperature and Entropy
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Volume/Pressure and Entropy
Volume/Pressure and Entropy
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Study Notes
Spontaneous Process
- A reaction that occurs under a given set of conditions is called a spontaneous reaction.
- A reaction that does not occur under specified conditions is said to be nonspontaneous.
- A water running downhill is spontaneous.
- A lump of sugar dissolving in a cup of hot coffee is spontaneous.
- Water freezes spontaneously below 0°C.
- Ice melts spontaneously above 0°C.
- Heat flows from a hotter object, not a colder one.
- Iron exposed to water and oxygen forms.
- Gathering of all the molecules into one is nonspontaneous.
Second Law of Thermodynamics
- The Second Law of Thermodynamics states that the entropy of the universe, as an isolated system, will always increase over time.
- Changes in the entropy in the universe can never be negative.
Entropy
- Entropy, S, is a thermodynamic quantity.
- Entropy measures how spread out or dispersed the energy of a system is.
- It describes if a process is spontaneous and can occur in a defined direction.
- Entropy is a state function.
- Entropy measures how random or disordered the system is.
Processes that lead to an increase in entropy of the system:
- Melting changes a solid to liquid.
- Vaporization changes a liquid to gas.
- Dissolving separates solute.
- Heating a system at T1 increases disorder.
Entropy Sign
- Entropy can be positive or negative.
- Positive entropy occurs when a system becomes more disordered.
- Negative entropy occurs when a system becomes less disordered or more ordered.
- Entropy is positive when melting, evaporation, and sublimation occurs.
- If a reaction produces more gas molecules than it consumes, ΔS° is positive.
- If there is no net change in the total number of gas molecules, then ΔS can be positive or negative, but will be relatively numerically small.
- Entropy can be negative when chemical substances undergo deposition, solidification, and condensation.
- If the total number of gas molecules diminishes, ΔS° is negative.
Factors that affect entropy:
- Physical state: (s) < (l) < (g)
- Amount of substance: more = greater entropy
- Temperature: higher T = greater entropy
- Volume/pressure: higher volume/lower pressure = greater entropy
Entropy Calculation
- Entropy can be calculated from the table of standard values using the formula: ΔS°rxn = Σ nS°(products) - Σ mS°(reactants)
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