Chemistry: Chemical Reactions

Question 1

What is a chemical reaction?

Answer 1

A process that rearranges the molecular or ionic structure of a substance, as opposed to a change in physical form.

Question 2

What are reactants?

Answer 2

The starting materials in a chemical reaction, shown on the left side of the equation.

Question 3

What are products?

Answer 3

The substances formed as a result of a chemical reaction, shown on the right side of the equation.

Question 4

What is a chemical equation?

Answer 4

A symbolic representation of a chemical reaction using chemical formulas.

Question 5

What does the arrow (→) mean in a chemical equation?

Answer 5

“Yields” or “produces.”

Question 6

What is the Law of Conservation of Mass?

Answer 6

In a chemical reaction, matter is neither created nor destroyed; the total mass of the reactants equals the total mass of the products.

Question 7

What does it mean to balance a chemical equation?

Answer 7

To ensure the number of atoms for each element is the same on both the reactant and product sides.

Question 8

What are coefficients in a chemical equation?

Answer 8

The numbers placed in front of chemical formulas to balance the equation.

Question 9

What is a synthesis (or combination) reaction?

Answer 9

A reaction where two or more simple substances combine to form a more complex substance. Example: A+B→AB.

Question 10

What is a decomposition reaction?

Answer 10

A reaction where a single compound breaks down into two or more simpler substances. Example: AB→A+B.

Question 11

What is a single replacement reaction?

Answer 11

A reaction where one element replaces another element in a compound. Example: A+BC→AC+B.

Question 12

What is a double replacement reaction?

Answer 12

A reaction where two compounds exchange ions to form two new compounds. Example: AB+CD→AD+CB.

Question 13

What is a combustion reaction?

Answer 13

A reaction where a substance reacts rapidly with an oxidant, usually oxygen, to produce heat and light.

Question 14

What are the products of the complete combustion of a hydrocarbon?

Answer 14

Carbon dioxide (CO2​) and water (H2​O).

Question 15

What is an exothermic reaction?

Answer 15

A reaction that releases energy, typically in the form of heat.

Question 16

What is an endothermic reaction?

Answer 16

A reaction that absorbs energy from its surroundings, typically as heat.

Question 17

What is a catalyst?

Answer 17

A substance that increases the rate of a chemical reaction without being consumed in the process.

Question 18

What is activation energy?

Answer 18

The minimum amount of energy required to start a chemical reaction.

Question 19

What is an oxidation-reduction (redox) reaction?

Answer 19

A reaction in which electrons are transferred between atoms.

Question 20

What is oxidation?

Answer 20

The loss of electrons.

Question 21

What is reduction?

Answer 21

The gain of electrons.

Question 22

What is a precipitate?

Answer 22

An insoluble solid that forms from a solution during a chemical reaction.

Question 23

What is a spectator ion?

Answer 23

An ion that exists as a reactant and a product in a chemical equation without undergoing any change.

Question 24

What is a net ionic equation?

Answer 24

An equation that shows only the species that are directly involved in the reaction.

Question 25

What is an acid-base reaction (neutralization)?

Answer 25

A reaction between an acid and a base that produces a salt and water.

Question 26

What is an acid?

Answer 26

A substance that donates protons (H+).

Question 27

What is a base?

Answer 27

A substance that accepts protons (H+).

Question 28

What are the common signs that a chemical reaction has occurred?

Answer 28

Color change, formation of a precipitate, gas production, temperature change, and light emission.

Question 29

What is reaction rate?

Answer 29

The speed at which a chemical reaction occurs.

Question 30

What factors can affect the rate of a chemical reaction?

Answer 30

Concentration, temperature, surface area, and catalysts.

Question 31

How does increasing the concentration of reactants affect the reaction rate?

Answer 31

It increases the rate by increasing the frequency of collisions between reactant particles.

Question 32

How does increasing the temperature affect the reaction rate?

Answer 32

It increases the rate by providing more kinetic energy to particles, leading to more frequent and energetic collisions.

Question 33

What is an irreversible reaction?

Answer 33

A reaction that proceeds in one direction until the reactants are completely converted into products.

Question 34

What is a reversible reaction?

Answer 34

A reaction that can proceed in both the forward and reverse directions.

Question 35

What is chemical equilibrium?

Answer 35

The state in a reversible reaction where the rates of the forward and reverse reactions are equal.

Question 36

What is a synthesis reaction of an acid and a base?

Answer 36

A neutralization reaction.

Question 37

What is an example of a synthesis reaction?

Answer 37

2Na+Cl2​→2NaCl.

Question 38

What is an example of a decomposition reaction?

Answer 38

2H2​O→2H2​+O2​.

Question 39

What is an example of a single replacement reaction?

Answer 39

Zn+2HCl→ZnCl2​+H2​.

Question 40

What is an example of a double replacement reaction?

Answer 40

AgNO3​+NaCl→AgCl+NaNO3​.

Question 41

What is the general form of an acid-base neutralization reaction?

Answer 41

Acid + Base → Salt + Water.

Question 42

What is a salt?

Answer 42

An ionic compound formed from an acid-base neutralization reaction.

Question 43

What is an oxidation state (or oxidation number)?

Answer 43

A number assigned to an element in a compound that represents the number of electrons lost or gained.

Question 44

In a redox reaction, which substance is the oxidizing agent?

Answer 44

The substance that is reduced (it causes another substance to be oxidized).

Question 45

In a redox reaction, which substance is the reducing agent?

Answer 45

The substance that is oxidized (it causes another substance to be reduced).

Question 46

What is a polymer?

Answer 46

A large molecule (macromolecule) composed of repeating structural units called monomers.

Question 47

What is a polymerization reaction?

Answer 47

A reaction in which monomers are linked together to form a polymer.

Question 48

What is an enzyme?

Answer 48

A biological catalyst.

Question 49

What is Le Châtelier's principle?

Answer 49

When a system at equilibrium is subjected to a change, it will adjust itself to counteract the change.

Question 50

What is a limiting reactant?

Answer 50

The reactant that is completely consumed in a chemical reaction and determines the amount of product formed.

Question 51

What is an excess reactant?

Answer 51

The reactant that is not completely consumed in a chemical reaction.

Question 52

What is the theoretical yield?

Answer 52

The maximum amount of product that can be formed from a given amount of reactants.

Question 53

What is the actual yield?

Answer 53

The amount of product actually obtained from a chemical reaction.

Question 54

What is the percent yield?

Answer 54

A measure of the efficiency of a reaction, calculated as ([TheoreticalYield/ActualYield​]×100%).