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Biblioteka

DE_Chem_Unit5

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Posljednje ažuriranje 7 months ago
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Pitanje 1
1.

Choose all the words that are in correct about the chemical reactions of CO2

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  • Carbon Emissions and Global Climate

    If you are driving in a gas-powered vehicle, the carbon emissions from your vehicle contribute to global climate change. Scientists associate these carbon emissions with atmospheric warming. However, there are also other effects of carbon emissions on the global climate. For example, atmospheric carbon dioxide (CO2) that dissolves in seawater contributes to ocean acidification. Although there is naturally a higher percentage of CO2 in seawater than in the atmosphere, the dissolving of atmospheric CO2 impacts the ocean environment and marine life.

    Carbon Dioxide in the Oceans

    Carbon Dioxide in the Oceans

    Unlike in the atmosphere, where there are only trace amounts of carbon dioxide, CO2 is one of the major gases dissolved in seawater. How do you think it interacts with the other molecules in the ocean?

    To understand ocean acidification, first consider the elements carbon (C), hydrogen (H), and oxygen (O) and the chemical structures of CO2 and water (H2O).

    The more molecules collide, the more bonds break and new bonds form, producing new molecules. Kinetic energy controls how fast molecules collide. Temperature is a measure of kinetic energy, and as it increases, the number of molecular collisions also increases. Consequently, higher temperatures yield greater instances of old bonds breaking and new bonds forming.

    Electronegativity refers to the tendency of atoms to attract and bond with electrons. Electronegativity results from the electron configuration of atoms. Atoms prefer to have eight electrons in their valence (outer) shell. H only has one electron in its outer shell, whereas O has six and C has four. This facilitates bonds between atoms as they share or gain/lose electrons.

    Covalent bonds occur when electron pairs are shared between elements. In each CO2 molecule, the C has four covalent bonds with two O atoms. In each H2O molecule, there are two covalent bonds, one between O and each H atom.

    When reactions occur, multiple reactants creating one product is called a combination reaction. Alternatively, one reactant producing multiple products is called a decomposition reaction. Substitution reactions also occur when elements of the reactants are exchanged. Consider the types of reactions that occur when CO2 undergoes chemical reactions in seawater.

    Carbon Dioxide

    Carbon Dioxide

    A molecule of carbon dioxide consists of a central carbon atom bonded to two oxygen atoms. What does this structure imply about how carbon dioxide might dissolve?

    Water

    Water

    A molecule of water consists of a central oxygen atom bonded to two hydrogen atoms. How does water’s structure impact how it dissolves other compounds?

    Element

    Electronic Configuration

    Group in the Periodic Table

    Carbon

    1s2 2s2 2p2

    14

    Hydrogen

    1s1

    1

    Oxygen

    1s2 2s2 2p4

    16

    If H loses its electron to a more electronegative element, it becomes an H+ ion. Dissolution of CO2 in seawater results in the production of a weak acid, carbonic acid (H2CO3). H2CO3 then rapidly dissolves. Consequently, excess H+ ions as well as bicarbonate (HCO3-1) and carbonate (CO3-2) salts are produced.

    Seawater is naturally basic. Prior to the Industrial Revolution, seawater had an average pH of approximately 8.2. Today, the average pH of seawater is approximately 8.1. Ocean acidification occurs because seawater pH is reduced by excess H+ ions that are produced from the dissolution of CO2 in seawater.

The ocean represents one part of the carbon cycle. The carbon cycle involves chemical reactions across various systems of Earth (atmosphere, hydrosphere, biosphere, and geosphere). Increased atmospheric CO2 leads to increased ocean acidification. However, all of Earth’s systems are interconnected, and atmospheric CO2 concentrations can change and be changed by other parts of the environment where carbon is stored.

Carbon Cycle

Carbon Cycle

  • The exchange of carbon dioxide between atmosphere and ocean, where large quantities of carbon are stored, is (a small) part of the complex carbon cycle. How else is carbon dioxide involved in this cycle?

Pitanje 2
2.

Include the correct balanced chemical reactions for the designated parts of the carbon cycle model.

  • CH4 + 2CO2 → CO2 + 2H2O

  • 6CO2 + 6H2O → C6H12O6 + 6O2

  • C6H12O6 → 6CO2 + 6H2O

  • Combustion of Fossil Fuels

  • Plant Respiration

  • Animal Respiration

  • Photosynthesis by Plants

  • Many chemical reactions in the environment are associated with human-mediated (or anthropogenic) factors. Such anthropogenic activities include, for example, combustion of fossil fuels and deforestation. Atmospheric greenhouse gases (such as CO2, the most influential greenhouse gas) trap heat. Therefore, increased greenhouse gas concentrations are strongly associated with increased temperatures.

    Atmospheric Carbon Dioxide Is Rising

    Atmospheric Carbon Dioxide Is Rising

    The technological, industrial, and economic changes of the last century have sharply increased the amount of CO2 emitted by human activities. What are the effects on the atmosphere and the hydrosphere?

    With increasing concentrations of greenhouse gases in the atmosphere, there are direct impacts on other components of the carbon cycle. As there are stresses on a system, the equilibrium of greenhouse gases shifts accordingly, which follows Le Chatelier’s Principle.

    For example, atmospheric CO2 and dissolved aqueous CO2 are in equilibrium. Consider what happens when there is increased atmospheric CO2. Dissolved CO2 may be rapidly released into the atmosphere by various components of the carbon cycle. Consequently, more atmospheric CO2 dissolves in water. The equilibrium is therefore maintained, but shifted so that there is both increased atmospheric and dissolved CO2.

    Because there is more atmospheric CO2 dissolved in water, there are more molecules in a given volume of seawater. Increased atmospheric CO2 causes temperatures to rise. This change in temperature, in addition to increased molecular density, affects the rate of molecular collisions in seawater.

    These processes also affect other parts of the carbon cycle. Increased CO2 dissolution in seawater and increased carbonic acid (H2CO3) concentrations produce excess H+ ions that react with minerals, such as those in rocks. The interaction of H+ ions and minerals can result in chemical weathering of these rocks.

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Pitanje 3
3.

  • Select the descriptions that best describe the outcomes of changes in atmospheric carbon concentration and temperature based on Le Chatelier’s Principle.

Pitanje 4
4.

Explain the effects of changing greenhouse gas concentrations on the rate at which reactions occur in the carbon cycle with emphasis on the collisions at the molecular level and based on Le Chatelier’s Principle, and provide an example of a reaction that would occur at a different rate.

Coral reefs are home to more than 25 percent of life in the oceans and provide food to people worldwide. Corals are symbiotic with photosynthetic algae. The corals provide shelter to the algae, and the algae are an important food source for corals. Greenhouse gas emissions can have two devastating effects on coral reefs. With increased ocean temperatures, the symbiotic algae leave, which causes coral bleaching. Corals cannot survive for long without their algal food source, and thus can die as a result. Ocean acidification can also weaken coral skeletons and inhibit growth. Corals use carbonate (CO ) and calcium (Ca ) ions for growth and skeletal integrity. Increased CO in oceans produces an increase in available bicarbonate ions (HCO ) but a decrease in available CO ions. Therefore, corals and other calcium carbonate shell-building organisms are at great risk from increased ocean temperatures.

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Pitanje 5
5.
Drugi mogući odgovor:

Although greenhouse gases are known to increase Earth’s temperatures, there are also molecules that can help reduce global temperatures. For example, atmospheric sulfur dioxide (SO ) can reflect heat away from Earth’s surface. This reflection helps cool the Earth’s surface. Although there are several sources of atmospheric sulfur, such as volcanic eruptions and the burning of coal, marine biogenic sulfur is the largest source

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Pitanje 6
6.

Arrange these statements about the cascade effects of increased 

CO2 on atmospheric sulfur in logical order.

  1. Both CO2 and SO2 naturally occur in the atmosphere.

  2. Atmospheric sulfur is reduced as a consequence of decreased marine biogenic sulfur production.

  3. Increased atmospheric CO2 is absorbed by seawater

  4. Increased CO2 in seawater yields decreased biogenic sulfur production.

  5. Temperatures further increase when there is less atmospheric sulfur.

All of Earth’s systems are interconnected. Therefore, all of Earth’s systems are affected by increased CO from human activity. In the ocean, increased CO has effects on both the hydrosphere (especially seawater) and geosphere (especially the seafloor) with respect to carbon storage. Over time, some carbon is taken up by organisms in the marine food web. When organisms die, they fall to the seafloor, where the carbon is transferred back to the geosphere. Consequently, the seafloor stores carbon

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Pitanje 7
7.
  • Coral reef deaths

  • Change in stored carbon compounds

  • Shell-building organism abundance

  • Seafloor sediment density

  • Chemical analysis

  • Mechanical testing

  • Specimen sampling

  • Genome sequencing