2B3 Basic Principles of Chemical Reactions

Question 1

What is a chemical reaction?

Answer 1

A process where reactants are transformed into new substances called products.

Chemical reactions involve the breaking and forming of chemical bonds.

Examples include combustion, synthesis, and decomposition reactions.

Question 2

What is a chemical equation?

Answer 2

A representation of a chemical reaction using symbols and formulas.

Chemical equations show the reactants, products, and their relationships in terms of atomic and molecular formulas.

Question 3

Define:

Reactant

Answer 3

A substance that undergoes transformation in a chemical reaction to form products.

Reactants are the starting materials in a chemical reaction that undergo change to form products.

Question 4

What is a product in a chemical reaction?

Answer 4

A substance that is formed as a result of a chemical reaction.

Products are the new substances produced after reactants undergo chemical change during a reaction.

Question 5

Fill in the blank:

In a chemical equation, the reactants are on the _____ side, and the products are on the _____ side.

Answer 5

left, right

Reactants are substances that undergo chemical changes, while products are the new substances formed after the reaction.

Question 6

What does the symbol “→” in a chemical equation represent?

Answer 6

Produces or yields

This arrow separates the reactants (on the left) from the products (on the right) in a chemical reaction.

Question 7

True or False:

In a chemical equation, the number of atoms of each element is conserved.

Answer 7

True

The law of conservation of mass states that matter is neither created nor destroyed in a chemical reaction, so the number of atoms of each element must remain the same before and after the reaction.

Question 8

What is the general format for writing a chemical equation?

Answer 8

Reactants → Products

Reactants are written on the left side of the equation, and products are written on the right side, separated by an arrow indicating the direction of the reaction.

Question 9

True or False:

The number of atoms of an element can change when balancing a chemical equation.

Answer 9

False

Balancing an equation involves adjusting coefficients, not changing subscripts in chemical formulas, to ensure the same number of atoms on both sides.

Question 10

How is a chemical equation balanced?

Answer 10

By adjusting the coefficients to equalize the number of atoms on both sides.

Coefficients are whole numbers used to balance the equation, ensuring the law of conservation of mass is followed.

Question 11

What is a coefficient in a chemical equation?

Answer 11

A number placed in front of a chemical formula to balance the equation.

Coefficients show the relative amounts of reactants and products involved in the reaction.

Question 12

What does the coefficient in a balanced equation represent?

Answer 12

The number of molecules or moles of a substance.

Coefficients indicate the relative amounts of reactants and products involved in the reaction, helping to balance the equation.

Question 13

Fill in the blank:

In balancing equations, coefficients must be written as _______ numbers.

Answer 13

whole

Coefficients must be integers (whole numbers) to maintain the proper ratio between reactants and products.

Question 14

In the equation 2H₂ + O₂ → 2H₂O, what is the coefficient of water (H₂O)?

Answer 14

2

The coefficient of 2 in front of H₂O indicates that two molecules of water are produced from the reaction of hydrogen and oxygen.

Question 15

True or False:

Balancing chemical equations involves changing the subscripts in chemical formulas.

Answer 15

False

Subscripts in chemical formulas represent the fixed number of atoms in a molecule and cannot be changed; only coefficients can be adjusted when balancing equations.

Question 16

Fill in the blank:

In a balanced chemical equation, the total mass of the _______ equals the total mass of the ________.

Answer 16

reactants, products

This reflects the principle of the conservation of mass, which states that mass is neither created nor destroyed during a chemical reaction.

Question 17

Define:

Stoichiometry

Answer 17

The calculation of the quantities of reactants and products in a chemical reaction.

Stoichiometry uses the relationships from a balanced equation to calculate amounts of substances involved in reactions.

Question 18

True or False:

Balancing chemical equations is necessary for performing stoichiometric calculations.

Answer 18

True

Balanced equations provide the correct proportions of reactants and products, which are crucial for determining quantities in mass-mole calculations.

Question 19

What is a combustion reaction?

Answer 19

A reaction with oxygen that produces heat, light, carbon dioxide, and water.

An example is the burning of methane: CH₄ + 2O₂ → CO₂ + 2H₂O.

Question 20

Fill in the blank:

A combustion reaction always involves a/an _______ and oxygen.

Answer 20

fuel

Fuels such as hydrocarbons, alcohols, or organic compounds undergo combustion with oxygen to release energy.

Question 21

What is a neutralization reaction?

Answer 21

A reaction between an acid and a base to produce water and a salt.

For example, HCl + NaOH → NaCl + H₂O, where hydrochloric acid neutralizes sodium hydroxide.

Question 22

What is a synthesis reaction?

Answer 22

Two or more substances combine to form a more complex product.

An example is 2H₂ + O₂ → 2H₂O, where hydrogen and oxygen combine to form water.

Question 23

True or False:

In a neutralization reaction, the products formed are water and a salt.

Answer 23

True

In neutralization, the hydrogen ions (H⁺) from the acid combine with hydroxide ions (OH⁻) from the base to form water.

Question 24

Fill in the blank:

A synthesis reaction is also called a ________ reaction.

Answer 24

combination

This is because two or more reactants combine to create a single product.

Question 25

What is a **decomposition** reaction?

Answer 25

A reaction where a **compound** breaks down into two or more simpler substances. ## Footnote For example, 2H₂O₂ → 2H₂O + O₂, where hydrogen peroxide decomposes into water and oxygen.

Question 26

# True or False: In a decomposition reaction, **energy** is often required to break bonds in the reactant.

Answer 26

True ## Footnote Decomposition reactions often require heat, light, or electricity to break the bonds of the reactant.

Question 27

What is a **single replacement** reaction?

Answer 27

A **reaction** where one element replaces another element in a compound. ## Footnote An example is Zn + 2HCl → ZnCl₂ + H₂, where zinc *replaces* hydrogen in hydrochloric acid.

Question 28

What is a **double replacement** reaction?

Answer 28

Two compounds **exchange** ions or elements to form two new compounds. ## Footnote An example is AgNO₃ + NaCl → AgCl + NaNO₃, where silver nitrate reacts with sodium chloride to form silver chloride and sodium nitrate.

Question 29

What type of reaction is represented by the equation, **Fe + CuSO₄ → FeSO₄ + Cu**?

Answer 29

Single replacement reaction ## Footnote In this reaction, iron (Fe) replaces copper (Cu) in copper sulfate (CuSO₄), forming iron sulfate (FeSO₄) and copper.

Question 30

What is an **oxidation-reduction** (redox) reaction?

Answer 30

A reaction where electrons are **transferred**, causing oxidation and reduction. ## Footnote Oxidation involves the loss of electrons, while reduction involves the gain of electrons.

Question 31

What is a **precipitation** reaction?

Answer 31

A reaction where two aqueous solutions **form** an insoluble solid (precipitate). ## Footnote Precipitation reactions often occur when ions in solution combine to form a compound that is not soluble in water.

Question 32

# Fill in the blank: In a **double replacement** reaction, the two compounds \_\_\_\_\_\_\_\_ ions to form new compounds.

Answer 32

exchange ## Footnote This type of reaction often produces a precipitate, gas, or water as a product.

Question 33

In an oxidation-reduction reaction, what happens to the substance that undergoes **oxidation**?

Answer 33

It **loses** electrons. ## Footnote For example, in the reaction 2Na + Cl₂ → 2NaCl, sodium (Na) loses electrons, becoming oxidized.

Question 34

What happens to the substance that undergoes **reduction** in a redox reaction?

Answer 34

It **gains** electrons. ## Footnote Reduction refers to the gain of electrons, which decreases the oxidation state of the substance involved.

Question 35

What is the term used for the substance that **gains** electrons in a redox reaction?

Answer 35

The **oxidizing** agent. ## Footnote The oxidizing agent causes the oxidation of another substance by accepting electrons.

Question 36

What is the term used for the substance that **loses** electrons in a redox reaction?

Answer 36

The **reducing** agent. ## Footnote The reducing agent causes the reduction of another substance by donating electrons.

Question 37

# Fill in the blanks: In the reaction **2Na + Cl₂ → 2NaCl**, sodium is \_\_\_\_\_\_\_\_ and chlorine is \_\_\_\_\_\_\_\_.

Answer 37

oxidized, reduced ## Footnote Sodium loses electrons (oxidation), while chlorine gains electrons (reduction) in the reaction.

Question 38

What is the **general equation** for combustion?

Answer 38

Fuel + O₂ → CO₂ + H₂O + energy ## Footnote This equation *represents* the combustion of hydrocarbons, such as methane, that produce carbon dioxide, water, and energy when they react with oxygen.

Question 39

What is the **first step** in a mass-to-mole calculation?

Answer 39

**Convert** the mass of the substance to moles using its molar mass. ## Footnote Use the formula: moles = mass (g) / molar mass (g/mol) to convert mass into moles before using stoichiometry.

Question 40

In the reaction **N₂ + 3H₂ → 2NH₃**, how many moles of nitrogen (N₂) are needed to react with 9 moles of hydrogen (H₂)?

Answer 40

3 ## Footnote According to the mole ratio, 1 mole of nitrogen reacts with 3 moles of hydrogen, so 9 moles of hydrogen would require 3 moles of nitrogen.

Question 41

# True or False: The law of conservation of mass is used in **mass-mole** calculations.

Answer 41

True ## Footnote Mass-mole calculations are based on the principle that mass is conserved in chemical reactions, meaning the mass of reactants equals the mass of products.

Question 42

If 32 grams of oxygen gas (O₂) react, how many **moles** of O₂ are involved?

Answer 42

1 ## Footnote The molar mass of O₂ is 32 g/mol, so 32 grams of O₂ is exactly 1 mole of O₂.

Question 43

What is a **mole-to-mole** ratio?

Answer 43

The **ratio** of moles of one substance to another in a balanced equation. ## Footnote It’s based on the coefficients of the balanced equation. For example, in: 2H₂ + O₂ → 2H₂O, * The ratio of H₂ to H₂O is 1:1. * The ratio of O₂ to H₂O is 1:2.

Question 44

In the reaction **N₂ + 3H₂ → 2NH₃**, how many moles of NH₃ will be produced from 6 moles of H₂?

Answer 44

4 ## Footnote The balanced equation shows a *3:2* mole ratio between H₂ and NH₃, so 6 moles of H₂ will produce 4 moles of NH₃.

Question 45

What is the mole-to-mole ratio in the reaction **2H₂ + O₂ → 2H₂O**?

Answer 45

2:1:2 (H₂:O₂:H₂O) ## Footnote The coefficients of the balanced equation give the **mole ratio**, meaning for every 2 moles of H₂, 1 mole of O₂ reacts to produce 2 moles of H₂O.

Question 46

In the equation **2H₂ + O₂ → 2H₂O**, what is the ratio of hydrogen (H₂) to oxygen (O₂)?

Answer 46

2:1 ## Footnote The coefficients show that two molecules of hydrogen react with one molecule of oxygen to form water.

Question 47

What is the **reaction rate**?

Answer 47

The **speed** at which reactants are converted into products. ## Footnote It can be measured by the change in concentration of reactants or products per unit time.

Question 48

Which **factors** can affect the rate of a chemical reaction?

Answer 48

* Concentration * Surface area * Temperature * Pressure * Activation energy * Catalysts ## Footnote These factors influence how often and how energetically particles collide.

Question 49

# True or False: Increasing the **concentration** of reactants increases the reaction rate.

Answer 49

True ## Footnote A *higher concentration* leads to more frequent collisions between reactant particles.

Question 50

# Fill in the blank: Increasing the \_\_\_\_\_\_ \_\_\_\_ of a **reactant** increases the reaction rate by exposing more particles to collisions.

Answer 50

surface area ## Footnote For example, powdered solids react faster than solid blocks because of their larger surface area.

Question 51

What is **activation energy**?

Answer 51

The **minimum** energy needed for a reaction to occur. ## Footnote If reactant particles don't have enough energy to overcome this barrier, no reaction will happen.

Question 52

How does **temperature** affect reaction rate?

Answer 52

Higher temperature **increases** reaction rate. ## Footnote Heat provides particles with more energy, making collisions more frequent and effective.

Question 53

# True or False: A catalyst is **consumed** during a reaction.

Answer 53

False ## Footnote A catalyst is a substance that increases the rate of a chemical reaction *without being consumed* in the process.

Question 54

# Fill in the blank: **Catalysts** work by providing a/an \_\_\_\_\_\_\_ reaction pathway with lower activation energy.

Answer 54

alternative ## Footnote This pathway increases the number of effective collisions.

Question 55

How does **pressure** affect the reaction rate in gases?

Answer 55

Increasing pressure **increases** reaction rate. ## Footnote Higher pressure forces particles closer together, leading to more frequent collisions.

Question 56

What is chemical **equilibrium**?

Answer 56

A **state** where the forward and reverse reaction rates are equal. ## Footnote At equilibrium, the concentrations of reactants and products remain constant over time.

Question 57

# Fill in the blank: **Le Chatelier's Principle** states that a system at equilibrium will adjust to \_\_\_\_\_\_\_ a disturbance.

Answer 57

counteract ## Footnote The system shifts to reduce the impact of changes in concentration, temperature, or pressure.

Question 58

What happens when **more reactants** are added to a system at equilibrium?

Answer 58

It shifts toward the **products**. ## Footnote Increasing reactant concentration drives the reaction forward to balance the system.

Question 59

What happens to equilibrium in an **exothermic reaction** if the temperature is increased?

Answer 59

It shifts toward the **reactants**. ## Footnote Heat acts as a **product** in exothermic reactions, so adding heat pushes the equilibrium backward.

Question 60

# Fill in the blank: In a system involving **gases**, increasing the pressure shifts equilibrium toward the side with \_\_\_\_\_\_\_ gas molecules.

Answer 60

fewer ## Footnote Higher pressure reduces the volume, so the system adjusts by favoring the side with fewer molecules.

Question 61

# True or False: Catalysts **change** the position of equilibrium.

Answer 61

False ## Footnote Catalysts **speed up** the attainment of equilibrium but do not alter the equilibrium position.

Question 62

What happens to equilibrium if the **concentration** of a product is increased?

Answer 62

It shifts toward the **reactants**. ## Footnote The system reduces the product concentration by favoring the reverse reaction.

Question 63

What is the effect of adding an **inert gas** at constant volume on the equilibrium position?

Answer 63

It has **no effect**. ## Footnote Inert gases *do not participate* in the reaction or alter the concentrations of reactants or products.

Question 64

In the reaction **N₂ + 3H₂ ⇌ 2NH₃**, what happens if the concentration of ammonia (NH₃) is **increased**?

Answer 64

The equilibrium shifts toward the **reactants**. ## Footnote According to *Le Chatelier's Principle*, increasing the concentration of products drives the reaction toward the reactants to balance the system.

Question 65

What is the **common ion** effect?

Answer 65

The **shift** in equilibrium caused by adding an ion already present in the system. ## Footnote For example, adding NaCl to a solution of AgCl decreases AgCl's solubility by increasing the concentration of Cl⁻ ions.

Question 66

# True or False: Catalysts are widely used in industrial processes to **increase** reaction rates.

Answer 66

True ## Footnote Catalysts like platinum in catalytic converters speed up reactions and save energy.

Question 67

Why does **refrigeration** slow down food spoilage?

Answer 67

Lower temperature **decreases** reaction rates. ## Footnote Cold temperatures *reduce* the energy of particles, making enzymatic and microbial reactions slower.

Question 68

What role do **catalysts** play in industrial processes like combustion?

Answer 68

It can **optimize** processes. ## Footnote In combustion, catalysts do not directly affect the combustion reaction itself but can help reduce harmful emissions and make the process more efficient.

Question 69

# True or False: **Enzymes** are biological catalysts that speed up reactions in the body.

Answer 69

True ## Footnote Enzymes lower activation energy, enabling faster biological processes like digestion.

Question 70

What happens to **equilibrium** in carbonated drinks when the bottle is opened?

Answer 70

Equilibrium shifts to **release** more CO₂ gas. ## Footnote In carbonated drinks, the dissolved CO₂ gas (carbon dioxide) is in equilibrium with the gas above the liquid. Lower pressure upon opening the bottle causes the system to shift, releasing CO₂ gas, which forms bubbles and creates the characteristic fizz.