$$80 \times (\frac{1}{2})^3$ = 10$$ grams

Question 1

Which of the following statements correctly describes the difference between a molecule and a compound?

Accepted Answer

A molecule is any group of atoms bonded together, while a compound is a substance consisting of two or more elements in a fixed ratio.

Question 2

Which four elements make up approximately 96% of living matter?

Accepted Answer

Carbon, Oxygen, Hydrogen, Nitrogen

Question 3

An atom of molybdenum has an atomic number of 42. If one isotope has a mass number of 98, how many neutrons does it have?

Accepted Answer

$$98 - 42 = 56$$ neutrons

Question 4

Which subatomic particle is responsible for the identity of an element?

Accepted Answer

Proton

Question 5

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

$$80 	imes (\frac{1}{2})^3$ = 10$$ grams

Question 6

Which of the following best explains why atoms are electrically neutral?

Accepted Answer

Atoms have equal numbers of protons and electrons.

Question 7

What is the electron configuration for a carbon atom (atomic number 6)?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^2$$

Question 8

Which type of chemical bond involves the sharing of electron pairs between atoms?

Accepted Answer

Covalent bond

Question 9

What is the main difference between polar and nonpolar covalent bonds?

Accepted Answer

Polar covalent bonds involve unequal sharing of electrons due to differences in electronegativity.

Question 10

Which of the following is NOT a property of salts (ionic compounds)?

Accepted Answer

They are considered molecules.

Question 11

Which intermolecular force is responsible for the attraction between water molecules?

Accepted Answer

Hydrogen bonds

Question 12

What is hybridization in the context of molecular bonding?

Accepted Answer

The process by which s and p orbitals combine to form new, hybrid orbitals for bonding.

Question 13

Which of the following best describes a chemical reaction at equilibrium?

Accepted Answer

The concentrations of reactants and products remain constant because the forward and reverse reactions occur at the same rate.

Question 14

A sodium atom loses one electron to become a sodium ion. What is the charge of the resulting ion?

Accepted Answer

$$+1$$

Question 15

Which of the following scenarios best illustrates the use of radioactive isotopes in medicine?

Accepted Answer

Using a radioactive tracer to follow the movement of a drug in the body.

Question 16

Which statement about van der Waals interactions is correct?

Accepted Answer

They result from temporary fluctuations in electron distribution, creating weak attractions between molecules.

Question 17

If an atom has 8 electrons, how many electrons are in its valence shell?

Accepted Answer

6

Question 18

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

Accepted Answer

Oxygen is more electronegative than hydrogen, causing unequal sharing of electrons.

Question 19

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

Accepted Answer

Iron (Fe)

Question 20

Which of the following is true about isotopes?

Accepted Answer

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

Chapter 2: The Chemical Context of Life – General Biology Study Notes

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