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Questions and Answers
Many of water's emergent properties, such as its cohesion, its high specific heat, and its high heat of vaporization, result from the fact that water molecules _____.
Many of water's emergent properties, such as its cohesion, its high specific heat, and its high heat of vaporization, result from the fact that water molecules _____.
are attracted to each other by partial negative and positive charges on the oxygen and hydrogen atoms, respectively
What useful quality is based on water's high specific heat?
What useful quality is based on water's high specific heat?
Organisms resist rapid temperature changes.
What is the arrow pointing to in the diagram?
What is the arrow pointing to in the diagram?
Hydrogen ion
What is the arrow pointing to in the diagram?
What is the arrow pointing to in the diagram?
In a neutral solution, the concentration of _____ is equal to the concentration of hydroxide ions.
In a neutral solution, the concentration of _____ is equal to the concentration of hydroxide ions.
How does the pH of the solution on the right compare with that of the solution on the left?
How does the pH of the solution on the right compare with that of the solution on the left?
Select the statement that best describes a buffer.
Select the statement that best describes a buffer.
Which statement is true of pH buffers?
Which statement is true of pH buffers?
How does a buffer system operate against decreases in pH?
How does a buffer system operate against decreases in pH?
Buffers work best when...
Buffers work best when...
How does the way a buffer stabilizes pH during addition of acid differ from addition of base?
How does the way a buffer stabilizes pH during addition of acid differ from addition of base?
Which answer helps to explain why all living cells need pH buffers?
Which answer helps to explain why all living cells need pH buffers?
To make a buffer, you need to...
To make a buffer, you need to...
A polar covalent bond between two atoms results from...
A polar covalent bond between two atoms results from...
All of the following statements help to explain why water molecules form hydrogen bonds except: Water is an electronegative molecule.
All of the following statements help to explain why water molecules form hydrogen bonds except: Water is an electronegative molecule.
Water molecules have a polarity, which allows them to be electrically attracted to other water molecules and other polar molecules by weak chemical bonds known as _____.
Water molecules have a polarity, which allows them to be electrically attracted to other water molecules and other polar molecules by weak chemical bonds known as _____.
If the molecular mass of a carbon atom is 12, the mass of a hydrogen atom is 1, and the mass of an oxygen atom is 16 daltons, how many molecules does one mole of table sugar (sucrose; C12H22O11) contain?
If the molecular mass of a carbon atom is 12, the mass of a hydrogen atom is 1, and the mass of an oxygen atom is 16 daltons, how many molecules does one mole of table sugar (sucrose; C12H22O11) contain?
Which of the following is a hydrophobic material?
Which of the following is a hydrophobic material?
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Study Notes
Water's Properties
- Water's emergent properties, including cohesion, high specific heat, and high heat of vaporization, stem from molecular attraction due to partial charges.
- Water's high specific heat allows organisms, primarily composed of water, to resist rapid temperature fluctuations.
Ions in Solution
- Hydrogen ions (H+) are indicated with a single arrow.
- Hydroxide ions (OH-) are identified by a double arrow.
- In a neutral solution, concentrations of hydrogen ions and hydroxide ions are equal.
pH and Buffers
- A solution with more hydrogen ions is acidic compared to a basic solution that has fewer hydrogen ions.
- Buffers resist pH changes by accepting hydrogen ions from acids and donating them when bases are present.
- pH buffers consist of weak acids and bases, providing stability in varying conditions.
- A buffering system requires undissociated acid (HA) and its dissociated ion (A-) to neutralize additional hydrogen ions.
- Optimal buffer function occurs when about half of the buffering molecules are dissociated.
Buffer Mechanisms
- Buffers stabilize pH by reversing reactions; donating ions during base addition and accepting them during acid addition.
- Living cells require pH buffers due to amino acids having varying carboxyl and amino groups, influencing overall pH balance.
- Creating a buffer involves using a weak acid or base that is partially ionized in water.
Chemical Bonds and Molecular Mass
- A polar covalent bond forms between atoms with differing electronegativities.
- Water molecules exhibit polarity, resulting in hydrogen bonding with other water and polar molecules; these are weak chemical bonds.
- One mole of sucrose (C₁₂H₂₂O₁₁) contains approximately 6.02 x 10²³ molecules, based on atomic masses (carbon 12, hydrogen 1, oxygen 16 daltons).
- Hydrophobic materials, such as wax, do not interact well with water, highlighting the importance of polarity in molecular interactions.
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