Question 1

Which of the following statements best explains why isotopes of the same element have different mass numbers but the same chemical properties?

Accepted Answer

Isotopes have different numbers of neutrons, which affects their mass but not their electron configuration.

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? Use the formula $$	ext{remaining mass} = 	ext{initial mass} 	imes (\frac{1}{2}$$)^{n}$$, where n$ is the number of half-lives.

Accepted Answer

20 grams

Question 3

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

Accepted Answer

A molecule is a group of atoms held together by covalent bonds, while a compound consists of two or more elements in a fixed ratio.

Question 4

Which of the following elements is NOT one of the four most abundant elements in living organisms?

Accepted Answer

Calcium

Question 5

How many electrons can the second electron shell of an atom hold?

Accepted Answer

8

Question 6

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

Accepted Answer

They have a full valence shell of electrons.

Question 7

A sodium atom (Na) has 11 protons and 12 neutrons. What is its atomic number and mass number?

Accepted Answer

Atomic number 11, mass number 23

Question 8

Which type of bond is formed when one atom donates an electron to another atom, resulting in oppositely charged ions that attract each other?

Accepted Answer

Ionic bond

Question 9

Which of the following is a property of salts (ionic compounds)?

Accepted Answer

They are stable when dry but dissociate easily in water.

Question 10

What is the electron configuration of carbon ($$Z=6$$)?

Accepted Answer

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

Question 11

Which of the following best describes a polar covalent bond?

Accepted Answer

Electrons are shared unequally, resulting in partial charges on the atoms.

Question 12

Which intermolecular force is primarily responsible for the ability of geckos to climb smooth surfaces?

Accepted Answer

Van der Waals interactions

Question 13

Which of the following is true about chemical reactions?

Accepted Answer

They involve the making and breaking of chemical bonds.

Question 14

If a radioactive isotope has a half-life of 3 hours, how many grams of a 48-gram sample will remain after 9 hours?

Accepted Answer

6 grams

Question 15

Which of the following best explains the concept of hybridization in chemical bonding?

Accepted Answer

It is the combination of s and p orbitals to form new, mixed orbitals for bonding.

Question 16

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

Accepted Answer

Iron

Question 17

Which of the following best describes a hydrogen bond?

Accepted Answer

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

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 statements about chemical equilibrium is correct?

Accepted Answer

At equilibrium, the forward and reverse reaction rates are equal.

Question 20

A patient is given a radioactive isotope for a diagnostic scan. If the isotope has a half-life of 8 hours and the initial dose is 32 mg, how much isotope will remain in the patient's body after 24 hours?

Accepted Answer

4 mg

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

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