Chemical Reactions: Types, Balancing Equations, and Energy Changes

Question 1

Which chemical equation represents a combustion reaction?

Accepted Answer

CH₄ + 2O₂ → CO₂ + 2H₂O

Answer

2H₂ + O₂ → H₂O

Answer

2Na + Cl₂ → 2NaCl

Answer

CaCO₃ → CaO + CO₂

Question 2

Which of the following reactions is a double displacement reaction?

Accepted Answer

D) NaOH + HCl → NaCl + H2O

Answer

A) 2Na + Cl2 → 2NaCl

Answer

B) 2H2O → 2H2 + O2

Answer

C) C + O2 → CO2

Question 3

Identify the single-replacement reaction from the following options:

Accepted Answer

Fe + 2HCl → FeCl2 + H2

Answer

2Na + Cl2 → 2NaCl

Answer

2H2O → 2H2 + O2

Answer

NH3 + HCl → NH4Cl

Question 4

Which type of chemical reaction produces multiple products from a single reactant?

Accepted Answer

Decomposition

Answer

Combination

Answer

Single displacement

Answer

Double displacement

Question 5

Which type of chemical reaction occurs when two or more substances combine to form a single new substance?

Accepted Answer

Combination

Answer

Decomposition

Answer

Combustion

Question 6

Which chemical equation represents a combustion reaction?

Accepted Answer

CH4 + 2O2 → CO2 + 2H2O

Answer

2Na + Cl2 → 2NaCl

Answer

Fe + CuSO4 → FeSO4 + Cu

Answer

2NH3 → N2 + 3H2

Question 7

Which of the following is NOT a recognized type of chemical reaction?

Accepted Answer

Transmutation

Answer

Combination

Answer

Decomposition

Answer

Single displacement

Question 8

Which type of chemical reaction involves the combination of multiple substances to form a single product?

Accepted Answer

Combination Reaction

Answer

Decomposition Reaction

Answer

Single Displacement Reaction

Answer

Double Displacement Reaction

Question 9

Which type of chemical reaction releases energy as heat?

Accepted Answer

Exothermic

Answer

Synthesis

Answer

Decomposition

Answer

Endothermic

Question 10

Which of the following chemical equations is balanced?

Accepted Answer

2H2 + O2 -> 2H2O

Answer

H2 + O -> H2O

Answer

H2O + O2 -> H2O2

Question 11

Which reaction type is NOT included in the list?

Accepted Answer

Transmutation

Answer

Synthesis

Answer

Decomposition

Answer

Combustion

Question 12

Exothermic reactions are characterized by which of the following?

Accepted Answer

Release of heat

Answer

Absorption of heat

Answer

Formation of a precipitate

Answer

Production of a gas

Question 13

What is the term for a substance that speeds up a reaction without being consumed?

Accepted Answer

Catalyst

Answer

Reactant

Answer

Product

Answer

Inhibitor

Question 14

Differentiate between chemical and physical changes. Which statement is correct?

Accepted Answer

Chemical changes alter composition, while physical changes do not.

Answer

Physical changes alter composition, while chemical changes do not.

Answer

Both changes alter composition.

Answer

Neither change alters composition.

Question 15

In a scientific experiment, what is the purpose of a control group?

Accepted Answer

To establish a baseline for comparison

Answer

To introduce bias into the experiment

Answer

To ensure accuracy of measurements

Answer

To speed up the reaction rate

Question 16

When working with chemicals in a lab, which safety precaution is essential?

Accepted Answer

Wearing gloves and safety glasses

Answer

Mixing chemicals in a closed container

Answer

Tasting unknown substances

Answer

Using bare hands to transfer chemicals

Question 17

Why is it crucial to balance chemical equations?

Accepted Answer

To ensure conservation of mass

Answer

To predict the products of a reaction

Answer

To determine the rate of a reaction

Answer

To identify the reactants of a reaction

Question 18

Which statement accurately describes exothermic reactions?

Accepted Answer

They release heat into the surroundings.

Answer

They absorb heat from the surroundings.

Answer

They do not involve a change in temperature.

Answer

They are always spontaneous.

Question 19

What is the primary role of a catalyst in a chemical reaction?

Accepted Answer

To decrease the activation energy of the reaction.

Answer

To increase the activation energy of the reaction.

Answer

To make the reaction less exothermic.

Answer

To prevent the reaction from occurring.

Question 20

Identify the strong electrolyte in the following list:

Accepted Answer

NaCl

Answer

CH3OH

Answer

NH3

Answer

CO2

Question 21

Identify the type of chemical reaction represented by the equation: CH4 + 2O2 -> CO2 + 2H2O.

Accepted Answer

Combustion

Answer

Decomposition

Answer

Synthesis

Answer

Single Replacement

Question 22

Provide an example of an endothermic reaction.

Accepted Answer

Dissolving ammonium chloride in water

Answer

Combustion of methane

Answer

Neutralization of an acid and a base

Answer

Condensation of water vapor

Question 23

What is the primary purpose of using a catalyst in a chemical reaction?

Accepted Answer

To decrease the activation energy of the reaction

Answer

To increase the activation energy of the reaction

Answer

To change the products of the reaction

Answer

To prevent the reaction from occurring

Question 24

Which of the following is a chemical property of potassium?

Accepted Answer

Highly reactive with water

Answer

Silvery-white appearance

Answer

Low melting point

Answer

High density

Question 25

Explain the fundamental difference between a chemical change and a physical change.

Accepted Answer

Chemical changes involve a change in the composition of matter, while physical changes do not.

Answer

Physical changes involve a change in the composition of matter, while chemical changes do not.

Answer

Chemical changes are always irreversible, while physical changes are always reversible.

Answer

Physical changes are always irreversible, while chemical changes are always reversible.

Question 26

Identify an example of a redox reaction.

Accepted Answer

Electrolysis of water

Answer

Precipitation of calcium carbonate

Answer

Dissolution of sugar in tea

Answer

Melting of ice

Question 27

Which of the following is NOT a type of chemical reaction?

Accepted Answer

Nuclear fusion: Two atomic nuclei combine to form a single, heavier nucleus.

Answer

Combination: Two or more substances combine to form a single, more complex substance.

Answer

Decomposition: A single substance breaks down into two or more simpler substances.

Answer

Single replacement: One element takes the place of another element in a compound.

Question 28

Which of the following is an exothermic reaction?

Accepted Answer

Burning of wood releases heat into the surroundings.

Answer

Dissolving sugar in water absorbs heat from the surroundings.

Answer

Freezing of water releases heat into the surroundings.

Answer

Melting of ice absorbs heat from the surroundings.

Question 29

What is the oxidation number of chromium in Cr₂O₇²⁻?

Accepted Answer

+6: Chromium has lost six electrons.

Answer

+3: Chromium has lost three electrons.

Answer

-3: Chromium has gained three electrons.

Answer

-6: Chromium has gained six electrons.

Question 30

Which of the following is a strong acid?

Accepted Answer

Hydrochloric acid ionizes completely in water, releasing H+ ions.

Answer

Acetic acid partially ionizes in water, releasing H+ ions.

Answer

Carbonic acid partially ionizes in water, releasing H+ ions.

Answer

Ammonia is a weak base and does not ionize significantly in water.

Question 31

Which of the following is a homogeneous mixture?

Accepted Answer

Salt dissolved in water forms a homogeneous mixture with no visible particles.

Answer

Sand and water form a heterogeneous mixture with visible particles.

Answer

Oil and vinegar form a heterogeneous mixture with visible layers.

Answer

Iron filings and sulfur powder form a heterogeneous mixture with visible components.

Question 32

What is the empirical formula for a compound with a molecular formula of C₆H₁₂O₆?

Accepted Answer

CH₂O: The empirical formula represents the simplest whole-number ratio of atoms.

Answer

C₂H₄O₂: This is not the simplest whole-number ratio of atoms.

Answer

C₃H₆O₃: This is not the simplest whole-number ratio of atoms.

Answer

C₄H₈O₄: This is not the simplest whole-number ratio of atoms.

Question 33

Which of the following is a limiting reactant in the reaction: 2Al + 3Cl₂ → 2AlCl₃?

Accepted Answer

Al: Aluminum is consumed completely before all the chlorine is used up.

Answer

Cl₂: Chlorine is consumed completely before all the aluminum is used up.

Answer

Both Al and Cl₂: Both reactants are consumed completely at the same time.

Answer

Neither Al nor Cl₂: Neither reactant is limiting in this reaction.

Question 34

Which of the following is NOT a type of chemical reaction?

Accepted Answer

Physical Transformation

Answer

Combination

Answer

Decomposition

Answer

Single-Replacement

Question 35

Which of the following is an example of an endothermic reaction?

Accepted Answer

Photosynthesis

Answer

Burning methane

Answer

Dissolving salt in water

Answer

Neutralizing acid and base

Question 36

What is the function of a catalyst in a chemical reaction?

Accepted Answer

Speeds up the reaction

Answer

Slows down the reaction

Answer

Changes products

Answer

Prevents the reaction

Question 37

What is the product of a neutralization reaction?

Accepted Answer

Salt

Answer

Acid

Answer

Base

Answer

Water

Question 38

Calculate the molar mass of sodium chloride (NaCl):

Accepted Answer

58.5 g/mol

Answer

23 g/mol

Answer

35.5 g/mol

Answer

117 g/mol

Question 39

Which of the following is an example of a redox reaction?

Accepted Answer

Rusting of iron

Answer

Burning methane

Answer

Dissolving sugar in water

Answer

Evaporation of water

Question 40

What is the pH of a solution with a hydrogen ion concentration of 1 x 10^-7 M?

Accepted Answer

7

Answer

0

Answer

14

Answer

Insufficient information

Question 41

Which of the following is NOT a type of chemical reaction commonly taught in high school chemistry?

Accepted Answer

Nuclear fusion

Answer

Combination

Answer

Decomposition

Answer

Single displacement

Question 42

Balance the following chemical equation for the combustion of methane: CH₄ + O₂ → CO₂ + H₂O

Accepted Answer

CH₄ + 2O₂ → CO₂ + 2H₂O

Answer

CH₄ + O₂ → CO₂ + H₂O

Answer

CH₄ + 2O₂ → CO + 2H₂O

Answer

CH₄ + O₂ → C + 2H₂O

Question 43

Which of the following is a characteristic of an exothermic reaction?

Accepted Answer

Releases heat

Answer

Absorbs heat

Answer

No change in temperature

Answer

Produces a precipitate

Question 44

Which of the following substances is commonly used as a catalyst in the Haber process?

Accepted Answer

Nickel

Answer

Iron

Answer

Hydrogen

Answer

Nitrogen

Question 45

Identify the redox reaction among the following options:

Accepted Answer

Fe + 2HCl → FeCl₂ + H₂

Answer

NaOH + HCl → NaCl + H₂O

Answer

CH₄ + 2O₂ → CO₂ + 2H₂O

Answer

2Na + Cl₂ → 2NaCl

Question 46

Which of the following is a strong acid?

Accepted Answer

Hydrochloric acid

Answer

Acetic acid

Answer

Carbonic acid

Answer

Phosphoric acid

Question 47

In the equation CH4 + 2O2 → CO2 + 2H2O, what is the coefficient in front of the methane molecule?

Accepted Answer

1

Answer

2

Answer

3

Answer

4

Question 48

When hydrogen and oxygen combine to form water, what type of reaction occurs?

Accepted Answer

Synthesis

Answer

Decomposition

Answer

Displacement

Answer

Combustion

Question 49

Which reaction releases energy in the form of heat?

Accepted Answer

Burning of wood

Answer

Melting of ice

Answer

Dissolving of salt

Answer

Formation of water from hydrogen and oxygen

Question 50

What do catalysts do in chemical reactions?

Accepted Answer

Decrease activation energy

Answer

Increase activation energy

Answer

Change the products

Answer

Provide energy

Question 51

What is the pH of a solution with a hydrogen ion concentration of 1 x 10^-9 M?

Accepted Answer

9

Answer

7

Answer

14

Answer

2

Question 52

Which compound contains only carbon and hydrogen atoms?

Accepted Answer

CH4

Answer

NaCl

Answer

CO2

Answer

H2O

Question 53

What is the hybridization of the nitrogen atom in ammonia?

Accepted Answer

sp3

Answer

sp

Answer

sp2

Answer

sp3d

Question 54

Identify the option that is NOT a recognized type of chemical reaction.

Accepted Answer

Evaporation

Answer

Combination

Answer

Decomposition

Answer

Neutralization

Question 55

In the chemical equation: 2H2 + O2 → 2H2O, what is the numerical coefficient that precedes oxygen (O2)?

Accepted Answer

2

Answer

1

Answer

3

Answer

4

Question 56

Which of the following reactions is endothermic in nature?

Accepted Answer

Melting of ice

Answer

Burning of propane

Answer

Dissolving sodium chloride in water

Answer

Condensation of water vapor

Question 57

What is the primary function of a catalyst in a chemical reaction?

Accepted Answer

To lower the activation energy required for the reaction

Answer

To increase the activation energy required for the reaction

Answer

To alter the products formed in the reaction

Answer

To prevent the reaction from taking place

Question 58

Calculate the molarity of a solution containing 0.1 moles of solute dissolved in 1 liter of solution.

Accepted Answer

0.1 M

Answer

0.01 M

Answer

1 M

Answer

10 M

Question 59

Identify the strong acid from the following options:

Accepted Answer

Hydrochloric acid

Answer

Acetic acid

Answer

Carbonic acid

Answer

Hydrofluoric acid

Question 60

Which of the following reactions is classified as a redox reaction?

Accepted Answer

Combustion of propane

Answer

Neutralization of an acid with a base

Answer

Dissolving sodium chloride in water

Answer

Condensation of water vapor

Question 61

Determine the oxidation number of nitrogen in nitric acid (HNO3).

Accepted Answer

+7

Answer

-3

Answer

+3

Answer

+5

Question 62

Which type of chemical reaction occurs when propane (C3H8) burns in the presence of oxygen (O2), resulting in the formation of carbon dioxide (CO2) and water (H2O)?

Accepted Answer

Combination Reaction

Answer

Decomposition Reaction

Answer

Single Displacement Reaction

Question 63

In a chemical reaction, reactants transform into products. What is the primary reason for balancing a chemical equation?

Accepted Answer

To ensure the conservation of mass and energy in the reaction

Answer

To predict the qualitative aspects of a chemical reaction

Answer

To determine the rate of a reaction

Answer

To understand the quantitative aspects of chemical reactions without balancing

Question 64

Identify the type of chemical reaction where two or more substances combine to form a single product:

Accepted Answer

Synthesis

Answer

Decomposition

Answer

Single-displacement

Answer

Double-displacement