Key Concepts in Chemistry: Master the Fundamentals of Matter and Reactions

Question 1

According to the particulate model, describe the motion of gas particles:

Accepted Answer

Moving randomly and independently

Answer

Arranged in a structured pattern

Answer

Packed closely together

Answer

Attracted to one another

Question 2

Classify the following process as either a physical or chemical change: Rusting of iron

Accepted Answer

Chemical change

Answer

Physical change

Question 3

Which scenario illustrates an exothermic reaction?

Accepted Answer

Fuel combustion

Answer

Salt dissolving in water

Answer

Alcohol evaporating

Answer

Acid-base neutralization

Question 4

Define the enthalpy change of a reaction:

Accepted Answer

Reactant and product heat content difference

Answer

Heat absorbed by reactants

Answer

Heat released by products

Answer

Total energy of the reaction

Question 5

Describe the function of a catalyst in a chemical reaction:

Accepted Answer

Decreases activation energy

Answer

Increases activation energy

Answer

Alters reaction products

Answer

Slows down reaction rate

Question 6

Classify the following acid as strong or weak: Hydrochloric acid

Accepted Answer

Strong acid

Answer

Weak acid

Question 7

Which of the following is not considered a state of matter?

Accepted Answer

Energy

Answer

Solid

Answer

Liquid

Answer

Gas

Question 8

The fundamental unit of an element that retains its chemical properties is a(n):

Accepted Answer

Atom

Answer

Molecule

Answer

Ion

Answer

Compound

Question 9

The energy required to break a bond between two atoms is known as:

Accepted Answer

Bond energy

Answer

Activation energy

Answer

Enthalpy change

Answer

Kinetic energy

Question 10

The equilibrium constant of a reaction provides information about:

Accepted Answer

The relative amounts of reactants and products at equilibrium

Answer

The direction in which the reaction will proceed

Answer

The rate at which the reaction occurs

Answer

The spontaneity of the reaction

Question 11

Which of the following is considered a weak acid?

Accepted Answer

Acetic acid

Answer

Hydrochloric acid

Answer

Sulfuric acid

Answer

Nitric acid

Question 12

Which of the following reactions is a redox reaction?

Accepted Answer

Oxidation of iron

Answer

Neutralization of an acid and a base

Answer

Precipitation of a metal hydroxide

Answer

Hydrolysis of an ester

Question 13

The empirical formula of a compound represents:

Accepted Answer

The simplest whole number ratio of atoms in a compound

Answer

The actual number and types of atoms in a molecule

Answer

The molecular mass of a compound

Answer

The percentage composition of a compound

Question 14

Which of the following is NOT a fundamental state of matter?

Accepted Answer

Plasma

Answer

Solid

Answer

Liquid

Answer

Gas

Question 15

The mass of an individual atom or molecule is typically expressed in:

Accepted Answer

Atomic mass units

Answer

Grams

Answer

Joules

Answer

Kilograms

Question 16

The change in energy of a closed system that accompanies a chemical reaction at constant temperature and pressure is known as:

Accepted Answer

Enthalpy

Answer

Entropy

Answer

Gibbs free energy

Answer

Activation energy

Question 17

Which of the following equations represents a balanced chemical equation?

Accepted Answer

H₂ + 2O → 2H₂O

Answer

2H₂ + O₂ → H₂O

Answer

H₂ + O₂ → H₂O₂

Answer

2H + O → H₂O

Question 18

A substance that increases the rate of a reaction without being consumed is called a:

Accepted Answer

Catalyst

Answer

Reactant

Answer

Product

Answer

Solvent

Question 19

The equilibrium constant for a reversible reaction represents:

Accepted Answer

The ratio of products to reactants at equilibrium

Answer

The rate of the forward reaction

Answer

The rate of the reverse reaction

Answer

The activation energy of the reaction

Question 20

Which of the following is a strong acid?

Accepted Answer

Hydrochloric acid

Answer

Ethanoic acid

Answer

Carbonic acid

Answer

Water

Question 21

The oxidation state of nitrogen in HNO₃ is:

Accepted Answer

+5

Answer

-3

Answer

0

Answer

+3

Question 22

A chemical reaction involves:

Accepted Answer

Rearrangement of atoms to form new substances with different properties

Answer

Gain or loss of electrons between atoms, resulting in the formation of ions

Answer

Change in physical state only, such as melting or freezing

Answer

Conversion of one form of energy to another, without any change in the composition of the reactants

Question 23

Exothermic reactions are characterized by the:

Accepted Answer

Release of heat into the surroundings

Answer

Absorption of heat from the surroundings

Answer

Release of light energy

Answer

Production of a gas

Question 24

Which of the following is considered a strong acid?

Accepted Answer

Hydrochloric acid

Answer

Acetic acid

Answer

Carbonic acid

Answer

Phosphoric acid

Question 25

A neutral solution has a pH of:

Accepted Answer

7

Answer

0

Answer

14

Answer

28

Question 26

Which of the following gases is a major contributor to the greenhouse effect?

Accepted Answer

Carbon dioxide

Answer

Oxygen

Answer

Nitrogen

Answer

Argon

Question 27

The mole concept is primarily used to:

Accepted Answer

Relate the mass of a substance to the number of particles (atoms or molecules) it contains

Answer

Determine the volume of a gas at a given temperature and pressure

Answer

Calculate the concentration of a solution in terms of molarity

Answer

Measure the energy released or absorbed during a chemical reaction

Question 28

Redox reactions involve:

Accepted Answer

Transfer of electrons between species, resulting in changes in their oxidation states

Answer

Neutralization of an acid and a base, leading to the formation of a salt and water

Answer

Combustion of a hydrocarbon fuel, producing carbon dioxide and water

Answer

Dissolving a salt in water, causing the ions to separate and become solvated

Question 29

Which of the following is a characteristic of a physical property?

Accepted Answer

Can be observed without changing the composition of the substance

Answer

Melting point

Answer

Solubility

Answer

Flammability

Question 30

What is the chemical formula for sodium chloride?

Accepted Answer

NaCl

Answer

Na2Cl

Answer

NaCl2

Answer

ClNa

Question 31

Which of the following is classified as a homogeneous mixture?

Accepted Answer

Salt water

Answer

Granite

Answer

Oil and water

Answer

Sand in water

Question 32

What is the energy change when a substance transforms from a liquid to a gas?

Accepted Answer

Endothermic

Answer

Adiabatic

Answer

Isothermal

Answer

Exothermic

Question 33

Which of the following chemical equations represents a redox reaction?

Accepted Answer

Fe + CuSO4 → FeSO4 + Cu

Answer

NaOH + HCl → NaCl + H2O

Answer

C + O2 → CO2

Answer

NH4Cl → NH3 + HCl

Question 34

Which of the following is considered a weak acid?

Accepted Answer

Ethanoic acid

Answer

Hydrochloric acid

Answer

Sulfuric acid

Answer

Nitric acid

Question 35

What is the pH of a 0.1 M solution of sodium hydroxide (NaOH)?

Accepted Answer

13

Answer

1

Answer

11

Answer

7

Question 36

Which of the following gases is considered a greenhouse gas?

Accepted Answer

Carbon dioxide

Answer

Oxygen

Answer

Nitrogen

Question 37

What is the term for the process by which plants utilize sunlight to convert carbon dioxide and water into glucose?

Accepted Answer

Photosynthesis

Answer

Fermentation

Answer

Combustion

Answer

Respiration