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Partially Correct

Great job!

You have a sealed container with a block of ice and liquid water at 0°C. Over time, the ice melts completely. Does the entropy of the system increase or decrease?

it increases

You correctly identified that the entropy increases when the ice melts.

I think that because:

Melting increases entropy

compared to ice, water molecules move around more freely, meaning more microstates and that means more entropy

Your justification provided is too brief and doesn't offer a molecular-level explanation. Think about how the number of available microstates changes when the molecules are in the liquid state vs. the solid state.

You've clearly identified the connection between the particle-level interpretation of melting and the corresponding increase in available space to occupy and consequently the increase in microstates. This is fundamental to understanding entropy.

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Answer

It increases

Reason

When the water becomes liquid, its molecules can move more freely and so they have more microstates that are possible

Student 1 10:32 AM

Answer

Actually, it stays the same

Reason

Both water and ice are made from the same stuff: H2O

Student 2 11:30 AM

Answer

It increases

Reason

When the ice turns into a liquid, the water molecules can slide around more easily and become random

Student 3 12:45 PM

Answer

It decreases

Reason

Water is hotter than ice

Student 4 1:00 PM

Answer

It increases

Reason

The molecules start moving faster and faster

Student 5 2:15 PM

Answer

It increases

Reason

When the water becomes liquid, its molecules can move more freely and so they have more microstates that are possible

Student 1 10:32 AM

Answer

Actually, it stays the same

Reason

Both water and ice are made from the same stuff: H2O

Student 2 11:30 AM

Answer

It increases

Reason

When the ice turns into a liquid, the water molecules can slide around more easily and become random

Student 3 12:45 PM

Answer

It decreases

Reason

Water is hotter than ice

Student 4 1:00 PM

Answer

It increases

Reason

The molecules start moving faster and faster

Student 5 2:15 PM

Answer

It increases

Reason

When the water becomes liquid, its molecules can move more freely and so they have more microstates that are possible

Student 1 10:32 AM

Answer

Actually, it stays the same

Reason

Both water and ice are made from the same stuff: H2O

Student 2 11:30 AM

Answer

It increases

Reason

When the ice turns into a liquid, the water molecules can slide around more easily and become random

Student 3 12:45 PM

Answer

It decreases

Reason

Water is hotter than ice

Student 4 1:00 PM

Answer

It increases

Reason

The molecules start moving faster and faster

Student 5 2:15 PM

AI Powered Feedback

Provide personalized feedback to every student automatically using advanced AI. Save time while maintaining quality and consistency in your assessments.

Correct 4 / 4

Change

Correctly stated that entropy increases as ice melts into liquid water.

Justification

Accurately identified the phase change as the key factor and explained that the liquid state allows for more molecular arrangements (microstates).

Incorrect 0 / 4

Change

Did not state that entropy increases. The correct answer is that entropy increases when ice melts.

Justification

Failed to mention the phase change and increase in molecular arrangements. Instead, merely noted both phases are H2O, which doesn't address why entropy increases.

Partially Correct 3 / 4

Change

Correctly stated that entropy increases as ice melts. Answer is concise and directly addresses the change.

Justification

Recognized the phase change and noted more molecular freedom, but using 'random' fails to connect this to microstates. In future responses, clearly reference that liquid phase permits more microstates.

Incorrect 0 / 4

Change

Stated that entropy decreases, but it increases when ice melts. The phase change creates more molecular arrangements.

Justification

Explanation 'Water is hotter than ice' doesn't provide molecular-level justification. Should reference phase change and increase in accessible microstates, not temperature differences.

Partially Correct 2 / 4

Change

Correctly identified that entropy increases.

Justification

Explanation about molecules moving faster is not acceptable. Should recognize that melting is a phase change that increases possible molecular arrangements at constant temperature.

Correct 4 / 4

Change

Correctly stated that entropy increases as ice melts into liquid water.

Justification

Accurately identified the phase change as the key factor and explained that the liquid state allows for more molecular arrangements (microstates).

Incorrect 0 / 4

Change

Did not state that entropy increases. The correct answer is that entropy increases when ice melts.

Justification

Failed to mention the phase change and increase in molecular arrangements. Instead, merely noted both phases are H2O, which doesn't address why entropy increases.

Partially Correct 3 / 4

Change

Correctly stated that entropy increases as ice melts. Answer is concise and directly addresses the change.

Justification

Incorrect 0 / 4

Change

Stated that entropy decreases, but it increases when ice melts. The phase change creates more molecular arrangements.

Justification

Explanation 'Water is hotter than ice' doesn't provide molecular-level justification. Should reference phase change and increase in accessible microstates, not temperature differences.

Partially Correct 2 / 4

Change

Correctly identified that entropy increases.

Justification

Explanation about molecules moving faster is not acceptable. Should recognize that melting is a phase change that increases possible molecular arrangements at constant temperature.

Correct 4 / 4

Change

Correctly stated that entropy increases as ice melts into liquid water.

Justification

Accurately identified the phase change as the key factor and explained that the liquid state allows for more molecular arrangements (microstates).

Incorrect 0 / 4

Change

Did not state that entropy increases. The correct answer is that entropy increases when ice melts.

Justification

Failed to mention the phase change and increase in molecular arrangements. Instead, merely noted both phases are H2O, which doesn't address why entropy increases.

Partially Correct 3 / 4

Change

Correctly stated that entropy increases as ice melts. Answer is concise and directly addresses the change.

Justification

Incorrect 0 / 4

Change

Stated that entropy decreases, but it increases when ice melts. The phase change creates more molecular arrangements.

Justification

Explanation 'Water is hotter than ice' doesn't provide molecular-level justification. Should reference phase change and increase in accessible microstates, not temperature differences.

Partially Correct 2 / 4

Change

Correctly identified that entropy increases.

Justification

Explanation about molecules moving faster is not acceptable. Should recognize that melting is a phase change that increases possible molecular arrangements at constant temperature.

If the

p K_{a}

H N O_{2}

is 3.35 and the pH of an

H N O_{2}

N a N O_{2}

solution is 3.25, which of the following is TRUE?

H N O_{2} < [N a N O_{2}]

H N O_{2} = [N a N O_{2}]

H N O_{2} > [N a N O_{2}]

H N O_{2} = 10 \cdot [N a N O_{2}]

b) I think this because:

I looked at the Henderson-Hasselbalch equation, pH = pKa + log(base/acid). Since 3.25 is less than 3.35, the log term must be negative, meaning [base]<[acid].

Key Relationship

If $p H < p K_{a}$ , what does this tell you about $l o g (\frac{[ A ^{-} ]}{[ H A ]})$ ?

Complete Answer

Your explanation correctly applies the Henderson-Hasselbalch equation and accurately interprets the relationship between pH, pKa, and the concentrations of the acid and base.

Rubric Item

$p H = p K_{a} + l o g (\frac{[ A ^{-} ]}{[ H A ]})$

Part a)

Recall that the Henderson-Hasselbalch equation states that $p H = p K_{a} + l o g (\frac{[ A ^{-} ]}{[ H A ]})$ . If $[H N O_{2}] < [N a N O_{2}]$ (i.e. $[H A] < [A^{-}]$ ), then the log term will yield a positive number and the pH will end up being greater than the pKa.

Part b)

Please get part a) right before attempting this explanation.

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Section	Start Date	Due Date	Grade Release
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12 156 53

Stoichiometry Basics 25

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45 89 55

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January 10, 2025 — April 1, 2025

78 92 34

Molecular Geometry 15

January 15, 2025 — March 30, 2025

23 45 107

Thermodynamics Principles 40

January 20, 2025 — April 5, 2025

89 67 42

Electrochemistry Fundamentals 35

January 25, 2025 — April 10, 2025

34 128 51

Kinetics and Reaction Rates 20

February 1, 2025 — April 15, 2025

92 68 27

Organic Functional Groups 30

February 5, 2025 — April 20, 2025

45 89 60

Quantum Chemistry 35

February 10, 2025 — April 25, 2025

67 98 41

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Class Average

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Lab Section Management

Section	Start Date	Due Date	Grade Release
Mon AM	March 24th, 10:00 AM	April 11th, 10:00 AM	April 13th, 12:00 PM
Mon PM	March 24th, 2:00 PM	April 11th, 2:00 PM	April 13th, 12:00 PM
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Balancing Reactions 20

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12 156 53

Stoichiometry Basics 25

January 5, 2025 — March 25, 2025

45 89 55

Upcoming

Acid-Base Titration 30

January 10, 2025 — April 1, 2025

78 92 34

Molecular Geometry 15

January 15, 2025 — March 30, 2025

23 45 107

Thermodynamics Principles 40

January 20, 2025 — April 5, 2025

89 67 42

Electrochemistry Fundamentals 35

January 25, 2025 — April 10, 2025

34 128 51

Kinetics and Reaction Rates 20

February 1, 2025 — April 15, 2025

92 68 27

Organic Functional Groups 30

February 5, 2025 — April 20, 2025

45 89 60

Quantum Chemistry 35

February 10, 2025 — April 25, 2025

67 98 41

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Task 4

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Class Average

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