Q22. Why is the acidification of seawater by absorbed CO2 a serious problem for life in the ocean?

Background

Topic: Ocean Acidification and Its Biological Impact

This question tests your understanding of how increased atmospheric CO2 leads to changes in ocean chemistry and the consequences for marine organisms.

Key Terms:

• Acidification: The process of becoming more acidic (lower pH).

• Carbonic acid: Formed when CO2 dissolves in water.

• Calcium carbonate: A compound used by marine organisms to build shells and skeletons.

Step-by-Step Guidance

1. Recall that when CO2 dissolves in seawater, it reacts with water to form carbonic acid ().

2. Understand that carbonic acid dissociates, releasing hydrogen ions (), which lowers the pH of seawater.

3. Consider how increased concentration affects the availability of carbonate ions (), which are needed by marine organisms to form calcium carbonate () structures.

4. Think about the impact on organisms like corals, mollusks, and some plankton that rely on calcium carbonate for their shells and skeletons.

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Q23. What was Stanley Miller trying to demonstrate with his famous experiment?

Background

Topic: Origin of Life and Prebiotic Chemistry

This question tests your knowledge of classic experiments that explored how organic molecules could form under early Earth conditions.

Key Terms:

• Stanley Miller experiment: A laboratory simulation of early Earth conditions.

• Abiotic synthesis: Formation of organic molecules from inorganic precursors without life.

Step-by-Step Guidance

1. Recall the setup: Miller used a mixture of gases thought to represent the early Earth's atmosphere (e.g., methane, ammonia, hydrogen, water vapor).

2. He applied electrical sparks to simulate lightning, providing energy for chemical reactions.

3. Consider what products were found after running the experiment for several days.

4. Think about what the presence of these products suggests about the origin of life's building blocks.

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Q24. What are the various kinds of isomers? What is the difference between cis and trans isomers?

Background

Topic: Isomerism in Organic Molecules

This question tests your understanding of structural diversity in organic chemistry and the significance of isomer types.

Key Terms:

• Isomers: Molecules with the same molecular formula but different structures or spatial arrangements.

• Structural isomers: Differ in covalent arrangement of atoms.

• Cis-trans (geometric) isomers: Differ in spatial arrangement around a double bond.

• Enantiomers: Mirror-image isomers (chiral molecules).

Step-by-Step Guidance

1. List the main types of isomers: structural isomers, cis-trans isomers, and enantiomers.

2. For cis-trans isomers, focus on molecules with double bonds that restrict rotation.

3. Describe how in cis isomers, similar groups are on the same side of the double bond, while in trans isomers, they are on opposite sides.

4. Think about how these differences can affect the physical and chemical properties of the molecules.

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Q25. What causes some molecules bonded to carbon to form a tetrahedral shape and some to form a planar (flat) shape?

Background

Topic: Molecular Geometry and Bonding in Organic Molecules

This question tests your understanding of how the type of chemical bonds around carbon atoms determines the 3D shape of molecules.

Key Terms and Concepts:

• Tetrahedral geometry: Four single bonds around a carbon atom ( hybridization).

• Planar geometry: Double bonds around a carbon atom ( hybridization).

• Bond hybridization: Mixing of atomic orbitals to form new hybrid orbitals.

Step-by-Step Guidance

1. Recall that carbon can form single, double, or triple bonds with other atoms.

2. When carbon forms four single bonds, the electron pairs arrange themselves as far apart as possible, resulting in a tetrahedral shape (bond angles of about 109.5°).

3. When carbon forms a double bond, the geometry around the double-bonded carbon is planar (bond angles of about 120°).

4. Think about how the type of hybridization ( for tetrahedral, for planar) determines the shape.

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Q26. What functional groups are always found in amino acids?

Background

Topic: Structure of Amino Acids

This question tests your knowledge of the basic components that make up all amino acids, which are the building blocks of proteins.

Key Terms:

• Functional group: A specific group of atoms within a molecule responsible for characteristic reactions.

• Amino group:

• Carboxyl group:

Step-by-Step Guidance

1. Recall the general structure of an amino acid: a central carbon atom bonded to four groups.

2. Identify the two functional groups that are always present: an amino group and a carboxyl group.

3. Remember that the other two groups are a hydrogen atom and a variable side chain (R group).

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Q27. Be able to recognize the functional groups in diagrams and be able to answer questions about the characteristics they give to the molecules they are attached to. (multiple questions)

Background

Topic: Functional Groups in Organic Molecules

This question tests your ability to identify common functional groups and understand how they influence the properties and reactivity of organic molecules.

Key Terms and Examples:

• Hydroxyl group: (alcohols; polar, forms hydrogen bonds)

• Carbonyl group: (aldehydes and ketones; polar)

• Carboxyl group: (carboxylic acids; acidic)

• Amino group: (amines; basic)

• Sulfhydryl group: (thiols; can form disulfide bonds)

• Phosphate group: (organic phosphates; involved in energy transfer)

• Methyl group: (affects gene expression, nonpolar)

Step-by-Step Guidance

1. Review the structure and properties of each functional group listed above.

2. Practice identifying these groups in structural diagrams of organic molecules.

3. Consider how each group affects the molecule's solubility, reactivity, and interactions with other molecules.

4. Think about examples of biological molecules that contain each functional group and the roles they play.

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