For the reaction N a C l ( s ) → w a t e r N a + ( a q ) + C l – ( a q ) , Δ H = +1 kcal/mol (+4.184 kJ/mol) NaCl\left(s\right)\xrightarrow{water}Na^{+}\left(aq\right)+Cl^{–}\left(aq\right),\Delta H=\text{+1 kcal/mol (+4.184 kJ/mol)} b. Does entropy increase or decrease in this process?

Welcome back everyone. The entropy change of the following reaction is positive 68.35 kilocalories per mole or positive 286 killed joules per mole is the entropy of the reaction increasing or decreasing. So for a reaction, we have solid silver sulfide, we have one mole of this reactant which forms or rather decomposes into two moles of our silver plus one caddy on which is Aquarius plus one mole of our sulfide to minus an ion, which is also Aquarius. Notice that on our reactant side, we go from a solid state to an a qui estate, we'll say equal right out Aquarius actually. And recall that Aquarius tells us that are substances are soluble in water, which is liquid. Recall that entropy describes the randomness or disorder of a system. And as far as our physical states of our compounds, our gaseous state of a compound has the highest amount of entropy more so than a Adam or compound in its liquid state. And compared to our liquid state, our solid state for any compound or atom will have the lowest amount of entropy. So we would say lowest entropy for solid state and highest entropy for a gaseous state. And again, entropy is represented by the symbol S. So because we went from a solid state on our reactant side to an Aquarius state. On our product side, we can therefore say that our entropy change is going to be positive. Because on our reactant side, we went from lower entropy in the solid state to higher entropy in a qui estates or soluble ions. And so therefore, entropy increases. So our final answer is going to be that entropy increases for our given reaction, which will correspond the choice a in the multiple choice as our final answer. So I hope this made sense and let us know if you have any questions.

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1. Matter and Measurements4h 31m
2. Atoms and the Periodic Table5h 23m
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7. Energy, Rate and Equilibrium

Entropy (Simplified)

GOB Chemistry

7. Energy, Rate and Equilibrium

Entropy (Simplified)

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2:21 minutes

Problem 37b

Textbook Question

For the reaction
$N a C l (s) \overset{w a t e r}{\to} N a^{+} (a q) + C l^{–} (a q), Δ H = +1 kcal/mol (+4.184 kJ/mol)$
b. Does entropy increase or decrease in this process?

Verified step by step guidance

Step 1: Understand the reaction. The reaction shows the dissolution of solid sodium chloride (NaCl) into its ions, sodium (Na⁺) and chloride (Cl⁻), in water. This process involves breaking the ionic lattice of NaCl and dispersing the ions into the solution.

Step 2: Recall the concept of entropy (S). Entropy is a measure of the disorder or randomness in a system. Processes that increase the number of particles or the distribution of energy typically result in an increase in entropy.

Step 3: Analyze the change in the system. In this reaction, a single solid (NaCl) is converted into two separate ions (Na⁺ and Cl⁻) in an aqueous solution. The ions are free to move in the solution, which increases the randomness and disorder of the system.

Step 4: Consider the physical states. Solids have a more ordered structure compared to ions in solution. The transition from a solid to dissolved ions represents a significant increase in disorder.

Step 5: Conclude the entropy change. Since the process involves breaking a solid lattice and dispersing ions into a more disordered state, the entropy of the system increases during this reaction.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Entropy

Entropy is a measure of the disorder or randomness in a system. In thermodynamics, it quantifies the number of ways a system can be arranged, with higher entropy indicating greater disorder. When a solid dissolves in a solvent, such as NaCl in water, the ions become more dispersed, typically leading to an increase in entropy.

Enthalpy Change (∆H)

Enthalpy change (∆H) refers to the heat absorbed or released during a chemical reaction at constant pressure. A positive ∆H, as in the case of NaCl dissolving in water, indicates that the process is endothermic, meaning it requires energy input. This energy is used to break the ionic bonds in the solid and to separate the ions in the solution.

Gibbs Free Energy (∆G)

Gibbs Free Energy (∆G) combines enthalpy and entropy to determine the spontaneity of a process. The relationship is given by the equation ∆G = ∆H - T∆S, where T is the temperature in Kelvin and ∆S is the change in entropy. A process is spontaneous if ∆G is negative, which can occur even if ∆H is positive, provided that the increase in entropy (∆S) is significant enough.