Chemistry Multiple Choice Questions - Part A

The subatomic particles in the nucleus of an oxygen atom include

• electrons, only

• neutrons, only

• protons and neutrons

• protons and electrons

Answer explanation

The nucleus of an oxygen atom contains protons and neutrons. Protons are positively charged, while neutrons have no charge. Electrons are found outside the nucleus, not within it.

Tags

NGSS.HS-PS1-4

NGSS.HS-PS1-8

Which phrase describes the charges and numbers of protons and electrons in an atom?

• have opposite charges and are equal in number

• have opposite charges and are unequal in number

• have the same charge and are equal in number

• have the same charge and are unequal in number

Answer explanation

In an atom, protons have a positive charge and electrons have a negative charge, making their charges opposite. They are equal in number, resulting in a neutral overall charge for the atom. Thus, the correct choice is 'have opposite charges and are equal in number'.

Tags

NGSS.HS-PS1-7

In the wave-mechanical model, which term identifies a region in an atom of lithium that is the most probable location of electrons in the ground state?

• hard sphere

• polar bond

• orbital

• spectrum

Answer explanation

In the wave-mechanical model, an 'orbital' refers to the region around the nucleus where electrons are most likely to be found in their ground state. This term accurately describes the probable locations of electrons in lithium.

An atom of C-12 in the ground state and an atom of C-13 in the ground state are defined as isotopes of carbon because these atoms have the same number of protons and ________

• the same number of neutrons

• the same number of electron shells

• a different number of neutrons

• a different number of electron shells

Answer explanation

C-12 and C-13 are isotopes of carbon because they have the same number of protons (6) but differ in the number of neutrons (C-12 has 6 neutrons, while C-13 has 7). Thus, they are defined as isotopes due to this difference.

At STP, which property can be used to differentiate between a 2.0-gram sample of oxygen, O2(g), and a 2.0-gram sample of helium, He(g)?

• mass

• temperature

• reaction with sodium

• phase of each sample

Answer explanation

At STP, helium and oxygen can be differentiated by their chemical reactivity. Helium is inert and does not react with sodium, while oxygen reacts vigorously with sodium, making this property a clear distinguishing factor.

How do the molecular structures and properties of oxygen, O2, and ozone, O3, compare?

• They have different molecular structures and the same properties.

• They have different molecular structures and different properties.

• They have the same molecular structure and the same properties.

• They have the same molecular structure and different properties.

Answer explanation

O2 (oxygen) has a diatomic structure, while O3 (ozone) has a triatomic structure. This difference leads to distinct properties: O2 is essential for respiration, whereas O3 is a pollutant and absorbs UV radiation, confirming they have different properties.

Tags

NGSS.HS-PS1-1

Which substance can be broken down by chemical means?

• aluminum

• ammonia

• argon

• arsenic

Answer explanation

Ammonia can be broken down into nitrogen and hydrogen through chemical reactions, such as decomposition. In contrast, aluminum, argon, and arsenic are elements that cannot be broken down by chemical means.

Tags

NGSS.MS-PS1-2

Which type of bonding is present in a sample of zinc at STP?

• covalent bonding

• hydrogen bonding

• ionic bonding

• metallic bonding

Answer explanation

Zinc exhibits metallic bonding, characterized by a sea of delocalized electrons that allow for conductivity and malleability. This type of bonding is typical in metals, distinguishing it from covalent, hydrogen, and ionic bonding.

Which formula represents a nonpolar molecule?

• CH4

• HCl

• H2O

• NH3

Answer explanation

CH4 (methane) is a nonpolar molecule because it has a symmetrical tetrahedral shape and the electronegativity difference between carbon and hydrogen is small, resulting in no net dipole moment. The other options are polar.

Given the equation representing a reaction: F + F → F₂ What occurs during this reaction?

• Energy is absorbed as a bond is formed.

• Energy is released as a bond is formed.

• Energy is absorbed as a bond is broken.

• Energy is released as a bond is broken.

Answer explanation

In the reaction F + F → F₂, energy is released when the bond between the two F atoms is formed, resulting in a more stable F₂ molecule. This is why the correct answer is that energy is released as a bond is formed.

Tags

NGSS.HS-PS1-4