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Ch. 2 - Water and Carbon: The Chemical Basis of Life
All textbooksFreeman 8th EditionCh. 2 - Water and Carbon: The Chemical Basis of LifeProblem 11
Chapter 2, Problem 11

Consider the reaction between carbon dioxide and water to form carbonic acid (CH2O3):


CO2(𝑔)+H2O(𝑙)β‡ŒCH2O3(π‘Žπ‘ž)


In the ocean, carbonic acid immediately dissociates to form a proton and bicarbonate ion, as follows:


CH2O3(π‘Žπ‘ž)β‡ŒCHO3βˆ’(π‘Žπ‘ž)+H+(π‘Žπ‘ž)


As atmospheric CO2 increases, the ocean absorbs more of the gas. Would this sequence of reactions be driven to the left or the right? How would this affect the pH of the ocean?

Verified step by step guidance
1
Identify the sequence of reactions: First, CO2 reacts with H2O to form carbonic acid (CH2O3). Then, carbonic acid dissociates into bicarbonate ion (CHO3βˆ’) and a proton (H+).
Understand Le Chatelier's Principle, which states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium moves to counteract the change.
Consider the effect of increasing atmospheric CO2: As more CO2 dissolves in the ocean, it shifts the first reaction (CO2 + H2O β‡Œ CH2O3) to the right, producing more carbonic acid.
Analyze the impact on the second reaction: With more carbonic acid being formed, the reaction (CH2O3 β‡Œ CHO3βˆ’ + H+) is also driven to the right, resulting in increased production of bicarbonate ions and protons.
Evaluate the effect on ocean pH: The increase in protons (H+) in the ocean lowers the pH, making the ocean more acidic.

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Key Concepts

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

Le Chatelier's Principle

Le Chatelier's Principle states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium shifts to counteract the change. In the context of the reaction between carbon dioxide and water, an increase in CO2 concentration will shift the equilibrium to the right, favoring the formation of carbonic acid and its dissociation products.
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Acid-Base Chemistry

Acid-base chemistry involves the study of proton donors (acids) and proton acceptors (bases). In the oceanic reaction, carbonic acid (H2CO3) acts as a weak acid, dissociating into bicarbonate (HCO3-) and protons (H+). The increase in H+ concentration from this dissociation leads to a decrease in pH, making the ocean more acidic.
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Ocean Acidification

Ocean acidification refers to the process by which the ocean becomes more acidic due to increased levels of CO2 in the atmosphere. As CO2 dissolves in seawater, it forms carbonic acid, which dissociates to release protons, lowering the pH. This phenomenon can have detrimental effects on marine life, particularly organisms that rely on calcium carbonate for their shells and skeletons.
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Related Practice
Textbook Question

Consider the reaction between carbon dioxide and water to form carbonic acid: CO2(g)+H2O(l)β‡ŒCH2O3(aq) In the ocean, carbonic acid immediately dissociates to form a proton and bicarbonate ion, as follows: CH2O3(aq)+H+(aq)β‡ŒCHO3βˆ’(aq) If an underwater volcano bubbled additional CO2 into the ocean, would this sequence of reactions be driven to the left or the right? How would this affect the pH of the ocean?

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Textbook Question

When H2 and CO2 react, acetic acid can be formed spontaneously while the production of formaldehyde requires an input of energy. Which of these conclusions can be drawn from this observation? a. More heat is released when formaldehyde is produced compared to the production of acetic acid. b.Compared to the reactants that it is formed from, formaldehyde has more potential energy than does acetic acid. c. Entropy decreases when acetic acid is produced and increases when formaldehyde is produced. d. Only acetic acid could be produced under conditions that existed in early Earth.

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Textbook Question

From what you have learned about water, why do coastal regions tend to have milder climates with cooler summers and warmer winters than do inland areas at the same latitude?

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Open Question

The current average pH of our oceans is 8.1. What is the concentration of protons in the oceans? How has the proton concentration changed in our oceans when compared to before the industrial revolution, when the average pH was 8.2? Express this change as a percentage increase.

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Open Question

Stony corals secrete thin layers of calcium carbonate (CaCO3) to build the foundation of coral reefs. The relationship between calcium carbonate, carbonic acid, and calcium bicarbonate (Ca(HCO3)2) is shown below:



CH2O3(π‘Žπ‘ž)+CaCO3(𝑠) β‡Œ Ca(HCO3)2(π‘Žπ‘ž)


Predict what will happen to the calcium carbonate foundation of reefs as CO2 levels rise in the oceans.

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Open Question

Data from the preceding experiment were collected at different times throughout each day over a period of one year under both present-day and estimated year 2100 conditions. Averages from these samples are provided in the following graph

Using the equation in Question 13, what do the positive and negative values indicate in terms of the directionality of this reaction? What implications do these data have on reef stability in the year 2100 if there is no intervention?

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