Question 1

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

Accepted Answer

NaCl is a compound, and compounds have emergent properties that differ from those of their individual elements due to chemical bonding.

Question 2

Which element is NOT one of the four that make up approximately 96% of living matter?

Accepted Answer

Calcium

Question 3

A radioactive isotope of carbon ($$^{14}C) is $$used in medical PET scans. What property of radioactive isotopes makes them useful as tracers in biological systems?

Accepted Answer

They decay spontaneously, emitting particles and energy that can be detected.

Question 4

Which of the following best describes the difference between an element and a compound?

Accepted Answer

A compound consists of two or more elements in a fixed ratio and has properties different from its constituent elements.

Question 5

A neutral atom of phosphorus has an atomic number of 15 and a mass number of 31. How many neutrons does it have?

Accepted Answer

16

Question 6

Which of the following best explains why noble gases such as neon are chemically inert?

Accepted Answer

They have a full valence electron shell, making them stable and unlikely to react.

Question 7

Which type of chemical bond involves the sharing of a pair of valence electrons between two atoms?

Accepted Answer

Covalent bond

Question 8

In a water molecule ($$H_2O$$), the oxygen atom is more electronegative than the hydrogen atoms. What is the result of this difference in electronegativity?

Accepted Answer

The oxygen atom acquires a partial negative charge, and the hydrogen atoms acquire partial positive charges.

Question 9

Which of the following is true about ionic bonds?

Accepted Answer

They result from the attraction between oppositely charged ions after one atom strips electrons from another.

Question 10

A scientist is using radiometric dating to determine the age of a fossil. If the half-life of the isotope is 5,000 years and only 25% of the original parent isotope remains, how many half-lives have passed?

Accepted Answer

2

Question 11

Which of the following best describes a hydrogen bond?

Accepted Answer

An attraction between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom.

Question 12

Which of the following is an example of a trace element required by humans in minute quantities?

Accepted Answer

Iron

Question 13

What is the main reason why van der Waals interactions can be collectively strong in biological systems?

Accepted Answer

They result from the cumulative effect of many weak interactions between molecules in close proximity.

Question 14

Which of the following equations correctly represents the photosynthesis reaction?

Accepted Answer

$$6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6$ + 6O_2$$

Question 15

Which statement about chemical reactions is correct?

Accepted Answer

Chemical equilibrium is reached when the forward and reverse reactions occur at the same rate.

Question 16

Which of the following best describes the role of electron orbitals in determining molecular shape?

Accepted Answer

The positions of atoms' orbitals determine the three-dimensional shape of a molecule, which is key to its function.

Question 17

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

Accepted Answer

Electrons farther from the nucleus have higher potential energy.

Question 18

A molecule of methane ($$CH_4) $$has a tetrahedral shape. What causes this specific molecular geometry?

Accepted Answer

The hybridization of s and p orbitals in the carbon atom.

Question 19

Which of the following best explains why morphine and endorphins can bind to the same receptors in the brain?

Accepted Answer

They have similar molecular shapes that allow them to fit into the same receptor sites.

Question 20

Which of the following is the correct definition of a cation?

Accepted Answer

An atom that has lost electrons and has a positive charge.

The Chemical Context of Life: Chapter 2 Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards