Question 1

Which chemical compound do wood ants (Formica rufa) use as a defense mechanism, and what property of this compound makes it effective against predators?

Accepted Answer

Formic acid; it releases $$\mathrm{H^+}$$ ions, making it acidic and causing a stinging sensation.

Question 2

Which of the following best explains why sodium chloride (NaCl) has properties different from its constituent elements, sodium and chlorine?

Accepted Answer

NaCl is a compound with emergent properties resulting from the chemical bonding of sodium and chlorine in a fixed ratio.

Question 3

A patient is diagnosed with goiter due to a deficiency of a trace element. Which element is most likely deficient, and what is its biological role?

Accepted Answer

Iodine; it is essential for thyroid hormone production.

Question 4

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 5

A radioactive isotope of carbon, $$^{14}\mathrm{C}$$, is used in radiometric dating. If the half-life of $$^{14}\mathrm{C} is 5$$,730 years, how much $$^{14}\mathrm{C}$$ remains after 17,190 years?

Accepted Answer

$$\frac{1}{8}$$

Question 6

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

Accepted Answer

A covalent bond involves the sharing of electrons, while an ionic bond involves the transfer of electrons and the attraction between oppositely charged ions.

Question 7

Why are noble gases such as neon (Ne) and argon (Ar) chemically unreactive?

Accepted Answer

They have full valence shells, making them stable and unlikely to form bonds.

Question 8

Which of the following best explains why serpentine-adapted plants can survive in soils toxic to most other plants?

Accepted Answer

They have evolved physiological adaptations through natural selection that allow them to tolerate high concentrations of toxic elements.

Question 9

Which of the following is true regarding the energy levels of electrons in an atom?

Accepted Answer

Electrons can only exist at specific energy levels called electron shells.

Question 10

Which of the following best describes a polar covalent bond?

Accepted Answer

A bond in which electrons are shared unequally, resulting in partial charges on the atoms.

Question 11

What is the main reason why water (H$$_2O) is a $$polar molecule?

Accepted Answer

Oxygen is more electronegative than hydrogen, so electrons are pulled toward oxygen, creating partial charges.

Question 12

Which of the following best explains why opiates such as morphine can bind to endorphin receptors in the brain?

Accepted Answer

Opiates have a similar molecular shape to endorphins, allowing them to fit into the same receptors.

Question 13

Which of the following is a real-world application of radioactive isotopes in medicine?

Accepted Answer

Using radioactive tracers to monitor metabolic activity in cancerous tissues with PET scans.

Question 14

Which of the following statements about chemical equilibrium is correct?

Accepted Answer

At equilibrium, the rates of the forward and reverse reactions are equal.

Question 15

Which of the following best describes the role of van der Waals interactions in biological systems?

Accepted Answer

They are weak interactions that, when numerous, can collectively stabilize large biological molecules or allow geckos to climb walls.

Question 16

Which of the following is the correct balanced equation for photosynthesis?

Accepted Answer

$$6 \mathrm{CO}_2 + 6 \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6 + 6 \mathrm{O}_2$$

Question 17

Which of the following best explains why electrons in the outermost shell (valence electrons) are important in chemical bonding?

Accepted Answer

They are the only electrons involved in forming chemical bonds with other atoms.

Question 18

Which of the following is a consequence of the law of conservation of matter in chemical reactions?

Accepted Answer

The total number of atoms is the same before and after the reaction.

Chapter 2: The Chemical Context of Life – Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards