Question 1

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

Accepted Answer

Isotopes have different numbers of neutrons, affecting 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 $$	ext{remaining mass} = 	ext{initial mass} 	imes \left(\frac{1}{2}\$$right)^{n}$$, where n$ is the number of half-lives.

Accepted Answer

10 grams

Question 3

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

Accepted Answer

A molecule is made of two or more atoms of the same element, while a compound is made 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

An atom of sodium (Na) has an atomic number of 11 and a mass number of 23. How many neutrons does it have?

Accepted Answer

12

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

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 8

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

Accepted Answer

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

Question 9

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

Accepted Answer

They are often found as crystals and dissociate easily in water.

Question 10

Which of the following best describes a polar covalent bond?

Accepted Answer

Electrons are shared unequally between atoms with different electronegativities.

Question 11

A hydrogen bond is most likely to form between which of the following pairs?

Accepted Answer

A hydrogen atom covalently bonded to oxygen and another oxygen atom.

Question 12

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

Accepted Answer

They allow molecules with temporary charge differences to stick together, such as a gecko climbing a wall.

Question 13

Which of the following statements about chemical reactions is correct?

Accepted Answer

Chemical reactions are reversible, and equilibrium is reached when the forward and reverse reaction rates are equal.

Question 14

If a radioactive isotope has a half-life of 3 days, how much of a 24 g sample will remain after 9 days?

Accepted Answer

3 g

Question 15

Which of the following best describes hybridization in the context of molecular bonding?

Accepted Answer

The mixing of s and p orbitals to form new, equivalent hybrid orbitals.

Question 16

Which of the following is an example of an intramolecular force?

Accepted Answer

Covalent bond

Question 17

A molecule of ammonia ($$NH_3) $$forms hydrogen bonds with water. Which property of ammonia allows this interaction?

Accepted Answer

The presence of a highly electronegative nitrogen atom bonded to hydrogen.

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?

Accepted Answer

Iron

Question 20

Which of the following best describes the relationship between atomic number and the identity of an element?

Accepted Answer

The atomic number is equal to the number of protons, which defines the element.

Chapter 2: The Chemical Context of Life – Study Notes

Guida di studio - Domande di pratica

Study guide - Flashcard