Q: A molecule has the formula $$C_6H_{12}O_6$. What is its molecular mass? (Atomic masses: C = 12, H = 1, O = 16)

$$(6 \times 12) + (12 \times 1) + (6 \times 16) = 180$$

Question 1

Which of the following best explains why ice floats on liquid water?

Accepted Answer

Ice is less dense than liquid water because its hydrogen bonds form a crystalline structure that spaces molecules farther apart.

Question 2

A radioactive isotope is used in medical imaging to trace the movement of a drug through the body. Which property of radioactive isotopes makes them useful for this purpose?

Accepted Answer

They emit detectable energy as they decay, allowing their location to be tracked.

Question 3

A solution is made by dissolving 10 grams of salt in 100 mL of water. In this scenario, which term correctly describes the salt?

Accepted Answer

Solute

Question 4

Which of the following best describes a polar covalent bond?

Accepted Answer

A bond in which electrons are shared unequally between two atoms due to differences in electronegativity.

Question 5

A patient is suffering from acidosis, a condition where blood pH drops below normal. Which biological mechanism helps resist changes in blood pH?

Accepted Answer

Buffers

Question 6

If a substance has a hydrogen ion concentration of $$1 	imes 10$$^{-5}$$ M, what is its pH?

Accepted Answer

$$5$$

Question 7

Which of the following is a trace element essential for human health, even though it is required only in small amounts?

Accepted Answer

Iron

Question 8

Which property of water allows trees to transport water from their roots to their leaves against gravity?

Accepted Answer

Cohesion and adhesion working together in capillary action

Question 9

A molecule has the formula $$C_6H_{12}O_6$. What is its molecular mass? (Atomic masses: C = 12, H = 1, O = 16)

Accepted Answer

$$(6 	imes 12) + (12 	imes 1) + (6 	imes 16) = 180$$

Question 10

Which of the following best describes the difference between an ionic bond and a covalent bond?

Accepted Answer

An ionic bond involves the transfer of electrons, while a covalent bond involves the sharing of electrons.

Question 11

Which of the following is an example of a nonpolar covalent bond?

Accepted Answer

The bond between two oxygen atoms in $$O_2$$

Question 12

Which of the following best explains why sweating cools the body?

Accepted Answer

Evaporative cooling removes heat as water molecules with the highest kinetic energy leave the skin.

Question 13

A student adds hydrochloric acid ($$HCl) to $$pure water, causing the pH to drop from 7 to 3. What happens to the concentration of hydrogen ions ($$[H^+]$$)?

Accepted Answer

It increases by a factor of $$10^4$$

Question 14

Which of the following is true about van der Waals interactions?

Accepted Answer

They are weak attractions that occur between molecules in close proximity.

Question 15

Which of the following best describes the role of electronegativity in chemical bonding?

Accepted Answer

It determines how strongly an atom attracts shared electrons in a covalent bond.

Question 16

Which of the following is a real-world consequence of acid precipitation?

Accepted Answer

It lowers the pH of soil and water, harming plants and aquatic life.

Question 17

A molecule has 8 protons, 8 neutrons, and 8 electrons. What is its atomic number and mass number?

Accepted Answer

Atomic number: $$8$$, Mass number: $$16$$

Question 18

Which of the following substances is hydrophobic?

Accepted Answer

Oil

Question 19

Which of the following best describes the relationship between a solute, solvent, and solution?

Accepted Answer

A solute dissolves in a solvent to form a solution.

Question 20

Which of the following is the correct structural formula for water?

Accepted Answer

H-O-H

The Chemical Context of Life & Water and Life: Study Notes

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