Question 1

Which of the following statements best explains why water is considered a polar molecule?

Accepted Answer

The oxygen atom in water attracts shared electrons more strongly than hydrogen, resulting in partial charges.

Question 2

A radioactive isotope has a half-life of 2 hours. If you start with 80 grams, how much will remain after 6 hours?

Accepted Answer

$$80 \div 2^3$ = 10$$ grams

Question 3

Which property of water is most directly responsible for the ability of some insects to walk on its surface?

Accepted Answer

Cohesion due to hydrogen bonding

Question 4

What is the molarity of a solution made by dissolving 29 grams of NaCl (molecular mass = 58 g/mol) in 1 liter of water?

Accepted Answer

$$M = \frac{29}{58} = 0.5 M$$

Question 5

Which of the following best describes the difference between covalent and ionic bonds?

Accepted Answer

Covalent bonds involve sharing electron pairs, while ionic bonds involve the transfer of electrons between atoms.

Question 6

A solution has $$[H^+] = 0.001 M. $$What is its pH?

Accepted Answer

$$pH = -\log_{10}(0.001) = 3$$

Question 7

Which emergent property of water helps stabilize Earth's climate and the temperature of living organisms?

Accepted Answer

High specific heat

Question 8

Which statement about trace elements is correct?

Accepted Answer

Trace elements are required in minute quantities but are essential for life.

Question 9

What is the main reason ice floats on liquid water?

Accepted Answer

Hydrogen bonds in ice form a crystalline lattice that spaces molecules apart, making ice less dense.

Question 10

Which of the following best describes a buffer in biological systems?

Accepted Answer

A buffer is a substance that minimizes changes in pH by accepting or donating $$H^+$$ ions.

Question 11

Which of the following is a consequence of water's high specific heat for living organisms?

Accepted Answer

Stable internal and external temperatures, protecting organisms from drastic changes.

Question 12

If a molecule is hydrophobic, what is its likely behavior in water?

Accepted Answer

It will repel water and not dissolve.

Question 13

Which of the following best explains why salt (NaCl) dissolves in water?

Accepted Answer

Water molecules form hydration shells around Na$$^+$$ and Cl$$^-$$ ions, separating them.

Question 14

Which of the following is true about hydrogen bonds?

Accepted Answer

Hydrogen bonds occur between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom.

Question 15

A solution is made by dissolving 0.5 moles of glucose in 2 liters of water. What is the molarity of the solution?

Accepted Answer

$$M = \frac{0.5}{2} = 0.25 M$$

Question 16

Which of the following best describes the role of adhesion in plants?

Accepted Answer

Adhesion allows water molecules to stick to plant cell walls, aiding in the upward movement of water.

Question 17

Which of the following is the correct definition of electronegativity?

Accepted Answer

The tendency of an atom to attract electrons in a covalent bond.

Question 18

Which of the following is NOT an emergent property of water?

Accepted Answer

Low surface tension

Question 19

What is the main biological importance of ice being less dense than liquid water?

Accepted Answer

It allows aquatic life to survive under the ice during winter.

Fundamental Chemical Principles and Water in Biology: Structured Study Notes

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