Chemical Reactions: Types, Balancing Equations, and Stoichiometry

Question 1

Which equation correctly represents the balanced chemical equation for the combustion of propane?

Accepted Answer

C3H8 + 5O2 → 3CO2 + 4H2O

Answer

C3H8 + 3O2 → 2CO2 + 3H2O

Answer

C3H8 + 4O2 → 3CO + 4H2O

Answer

C3H8 + 2O2 → CO2 + 2H2O

Question 2

When sodium reacts with water, what products are formed?

Accepted Answer

Sodium hydroxide and hydrogen gas

Answer

Sodium oxide and water vapor

Answer

Sodium chloride and oxygen gas

Answer

Sodium carbonate and hydrogen gas

Question 3

In a chemical reaction, 2 moles of sodium (Na) react with excess water (H2O) to produce sodium hydroxide (NaOH). How many moles of sodium hydroxide are formed?

Accepted Answer

2 moles

Answer

1 mole

Answer

4 moles

Answer

The question cannot be answered without more information.

Question 4

Based on the collision theory, how does an increase in temperature affect the rate of a chemical reaction?

Accepted Answer

Increases the number of effective collisions and the proportion of collisions with enough energy to react.

Answer

Reduces the number of effective collisions.

Answer

Only affects the number of effective collisions.

Answer

Only affects the proportion of collisions with enough energy to react.

Question 5

How does a catalyst influence the activation energy of a chemical reaction?

Accepted Answer

Lowers the activation energy, speeding up the reaction.

Answer

Raises the activation energy, slowing down the reaction.

Answer

Has no effect on activation energy but increases the number of reactants.

Question 6

In chemical reactions, what is dynamic equilibrium? Explain how the forward and reverse reactions occur simultaneously and how the equilibrium position is established.

Accepted Answer

In dynamic equilibrium, the forward and reverse reactions occur simultaneously at equal rates, resulting in no net change in the concentrations of the reactants and products.

Answer

Dynamic equilibrium is established when the concentrations of the reactants and products become equal.

Answer

Dynamic equilibrium is only possible in closed systems where no mass can enter or leave the system.

Answer

In dynamic equilibrium, the forward reaction is always faster than the reverse reaction.

Question 7

A chemical reaction between hydrochloric acid and magnesium metal speeds up when the temperature rises. Which explanation best describes this observation?

Accepted Answer

Higher temperature gives reactant molecules more kinetic energy, helping them overcome the activation energy barrier.

Answer

Higher temperature increases reactant molecule concentration, leading to more collisions and a faster reaction.

Answer

Higher temperature weakens reactant molecule bonds, making them more likely to react.

Answer

Higher temperature increases reactant molecule surface area, providing more reaction sites.

Question 8

Consider the reversible reaction: 2NO2(g) <=> N2O4(g). According to Le Chatelier's principle, which way will the equilibrium shift if pressure is increased?

Accepted Answer

Right, favoring N2O4

Answer

Left, favoring NO2

Answer

No shift in equilibrium

Question 9

Identify the type of chemical reaction represented by the following equation:

2KClO3 -> 2KCl + 3O2

Accepted Answer

Decomposition

Answer

Combination

Answer

Single displacement

Answer

Double displacement

Question 10

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

Accepted Answer

Triple Replacement

Answer

Combination

Answer

Decomposition

Answer

Single Displacement

Question 11

In the balanced chemical equation 4Fe + 3O2 -> 2Fe2O3, what is the coefficient in front of Fe?

Accepted Answer

4

Answer

2

Answer

6

Answer

8

Question 12

In a combustion reaction, which substance reacts with oxygen?

Accepted Answer

Fuel

Answer

Product

Answer

Inert

Answer

Catalyst

Question 13

Which of the following is a strong acid?

Accepted Answer

Hydrochloric acid

Answer

Acetic acid

Answer

Carbonic acid

Answer

Ammonia

Question 14

Which of the following is a redox reaction?

Accepted Answer

Fe + CuSO4 -> FeSO4 + Cu

Answer

2Na + 2H2O -> 2NaOH + H2

Answer

NaCl + AgNO3 -> AgCl + NaNO3

Answer

CH4 + 2O2 -> CO2 + 2H2O

Question 15

What is the hybridization of the carbon atom in methane (CH4)?

Accepted Answer

sp3

Answer

sp

Answer

sp2

Answer

sp3d

Question 16

Which of the following is a polar molecule?

Accepted Answer

H2O

Answer

CO2

Answer

CH4

Answer

N2

Question 17

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

Accepted Answer

Decreases the activation energy

Answer

Increases the activation energy

Answer

Changes the products of the reaction

Answer

Decreases the rate of the reaction

Question 18

`Which of the following is a type of chemical reaction in which two or more substances combine to form a single product?`

Accepted Answer

Synthesis

Answer

Decomposition

Answer

Single displacement

Answer

Double displacement

Question 19

`An endothermic reaction is one in which heat is: `

Accepted Answer

Absorbed

Answer

Released

Answer

Neither absorbed nor released

Answer

Always released

Question 20

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

Accepted Answer

Fe2O3 + 3CO → 2Fe + 3CO2

Answer

2Na + Cl2 → 2NaCl

Answer

CH4 + 2O2 → CO2 + 2H2O

Answer

HCl + NaOH → NaCl + H2O

Question 21

`What is the oxidation number of nitrogen in NH3?`

Accepted Answer

-3

Answer

+3

Answer

-5

Answer

+5

Question 22

`Which of the following is a catalyst?`

Accepted Answer

A substance that speeds up a reaction

Answer

A substance that slows down a reaction

Answer

A substance that is consumed in a reaction

Answer

A substance that is produced in a reaction

Question 23

`The activation energy of a reaction is:`

Accepted Answer

The minimum amount of energy required for a reaction to occur

Answer

The maximum amount of energy released in a reaction

Answer

The difference in energy between the reactants and products

Answer

The energy of the transition state

Question 24

How do catalysts affect chemical reactions?

Accepted Answer

Provide an alternative pathway with lower activation energy, increasing the reaction rate

Answer

Increase activation energy, slowing the reaction

Answer

Are consumed during the reaction, altering stoichiometry

Answer

Increase the number of collisions between reactant molecules, enhancing the reaction rate

Question 25

Which of the following actions will reduce the solubility of PbCl2 in water?

Accepted Answer

Adding Pb2+ ions

Accepted Answer

Adding Cl- ions

Answer

Adding HCl

Answer

Adding Pb(NO3)2

Question 26

Which intermolecular force (IMF) creates the strongest attraction between molecules?

Accepted Answer

Hydrogen bonding

Answer

Dipole-dipole interactions

Answer

London dispersion forces

Question 27

What formula calculates the percent yield of a chemical reaction?

Accepted Answer

Percent yield = (Actual yield / Theoretical yield) x 100%

Answer

Percent yield = (Theoretical yield / Actual yield) x 100%

Answer

Percent yield = Actual yield - Theoretical yield

Question 28

In the balanced chemical equation 2Al + 3Cl₂ → 2AlCl₃, what is the mole ratio of aluminum (Al) to chlorine (Cl₂)?

Accepted Answer

2:3

Answer

1:1

Answer

1:2

Answer

3:2

Question 29

In the reaction 2A + B → C + D, which change would speed up the reaction?

Accepted Answer

Adding a catalyst

Answer

Lowering the temperature

Answer

Reducing the amount of reactant A

Answer

Decreasing the surface area of reactant B

Question 30

Which graph accurately depicts the relationship between temperature and reaction rate?

Accepted Answer

Graph with a linear increase in reaction rate as temperature rises

Answer

Graph with a parabolic increase in reaction rate as temperature rises

Answer

Graph with a constant reaction rate regardless of temperature

Question 31

Balance the following chemical equation: Fe + O2 -> Fe2O3

Accepted Answer

4Fe + 3O2 -> 2Fe2O3

Answer

Fe + O2 -> Fe2O3

Answer

2Fe + O2 -> Fe2O3

Answer

8Fe + 6O2 -> 4Fe2O3

Question 32

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

Accepted Answer

Melting of ice

Answer

Combustion of propane

Answer

Dissolution of salt in water

Answer

Formation of sodium chloride

Question 33

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

Accepted Answer

To speed up the reaction

Answer

To slow down the reaction

Answer

To change the products of the reaction

Answer

To prevent the reaction from occurring

Question 34

Which of the following factors does NOT affect the rate of a chemical reaction?

Accepted Answer

Volume of the reaction vessel

Answer

Concentration of reactants

Answer

Temperature

Answer

Nature of the catalyst

Question 35

What is the main purpose of a titration experiment?

Accepted Answer

To determine the concentration of an unknown solution

Answer

To prepare a solution with a known concentration

Answer

To measure the volume of a gas

Answer

To identify an unknown compound

Question 36

What is the oxidation state of nitrogen in HNO3?

Accepted Answer

+5

Answer

-3

Answer

-2

Answer

+3

Question 37

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

Accepted Answer

7

Answer

0

Answer

14

Answer

-7

Question 38

In the reaction A(g) + 2B(g) → C(g) + D(g), the rate law is determined to be Rate = k[A][B]². What is the reaction order with respect to reactant A and reactant B, respectively?

Accepted Answer

First order with respect to A and second order with respect to B

Answer

Zero order with respect to A and first order with respect to B

Answer

Second order with respect to A and zero order with respect to B

Answer

First order with respect to both A and B

Question 39

Which of the following is the odd one out among types of chemical reactions?

Accepted Answer

Evaporation

Answer

Synthesis

Answer

Decomposition

Answer

Combustion

Question 40

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

Accepted Answer

2

Answer

1

Answer

3

Answer

4

Question 41

Calculate the molar mass of sodium chloride (NaCl) to the nearest whole number.

Accepted Answer

58 g/mol

Answer

23 g/mol

Answer

35 g/mol

Answer

71 g/mol

Question 42

In the reaction 2Mg + O2 → 2MgO, if 2.4 g of Mg and 1.6 g of O2 are used, which reactant is limiting?

Accepted Answer

Magnesium (Mg)

Answer

Oxygen (O2)

Answer

Neither Mg nor O2

Answer

Cannot be determined

Question 43

Which type of reaction is observed when sodium metal reacts explosively with water?

Accepted Answer

Redox reaction

Answer

Acid-base reaction

Answer

Precipitation reaction

Answer

Combustion reaction

Question 44

Which of the following factors does NOT affect the rate of a chemical reaction?

Accepted Answer

Color of the container

Answer

Temperature

Answer

Concentration

Answer

Surface area

Question 45

What is the enthalpy change for an exothermic reaction?

Accepted Answer

Negative

Answer

Positive

Answer

Zero

Answer

Cannot be determined

Question 46

Balance the following redox reaction in a basic solution: MnO₄^- + I^- → MnO₂ + I₂

Accepted Answer

2 MnO₄^- + 10 I^- + 8 OH^- → 2 MnO₂ + 5 I₂ + 4 H₂O

Answer

MnO₄^- + 2 I^- + 2 H⁺ → MnO₂ + I₂ + H₂

Answer

2 MnO₄^- + 5 I^- + 6 H⁺ → 2 MnO₂ + 5 I₂ + 3 H₂O

Answer

MnO₄^- + 4 I^- → MnO₂ + 4 I₂ + O₂

Question 47

How does an increase in temperature typically impact the rate of a chemical reaction?

Accepted Answer

It lowers the activation energy, resulting in a faster reaction rate.

Answer

It raises the activation energy, causing the reaction rate to decrease.

Answer

It has no effect on the activation energy, and the reaction rate stays the same.

Question 48

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

Accepted Answer

Oxidation

Answer

Combination

Answer

Decomposition

Answer

Single-replacement

Question 49

When balancing chemical equations, the coefficients represent the:

Accepted Answer

Molar ratios of reactants and products

Answer

Mass ratios of reactants and products

Answer

Volume ratios of reactants and products

Answer

Concentration ratios of reactants and products

Question 50

Which of the following is the balanced chemical equation for the combustion of methane?

Accepted Answer

CH4 + 2O2 -> CO2 + 2H2O

Answer

CH4 + O2 -> CO2 + H2O

Answer

CH4 + 3O2 -> CO2 + 2H2O

Answer

2CH4 + 3O2 -> 2CO2 + 2H2O

Question 51

Stoichiometry is the study of:

Accepted Answer

The quantitative relationships between reactants and products in chemical reactions

Answer

The rates of chemical reactions

Answer

The equilibrium of chemical reactions

Answer

The energy changes in chemical reactions

Question 52

In a combustion reaction, a substance reacts with:

Accepted Answer

Oxygen

Answer

Water

Answer

Carbon dioxide

Answer

Hydrogen

Question 53

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

Accepted Answer

Fe2O3 + 3CO -> 2Fe + 3CO2

Answer

2Na + Cl2 -> 2NaCl

Answer

CH4 + 2O2 -> CO2 + 2H2O

Answer

HCl + NaOH -> NaCl + H2O

Question 54

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

Accepted Answer

Releases heat

Answer

Absorbs heat

Answer

No change in temperature

Answer

Increases in volume

Question 55

The activation energy of a reaction is the:

Accepted Answer

Minimum energy required for a reaction to occur

Answer

Maximum energy released in a reaction

Answer

Rate constant for a reaction

Answer

Equilibrium constant for a reaction

Question 56

How does resonance contribute to the stability of benzene?

Accepted Answer

Resonance delocalizes electrons, which lowers the potential energy and increases the stability of the molecule.

Answer

Resonance allows electrons to flow more freely, making the molecule more reactive.

Answer

Resonance creates a permanent dipole moment in the molecule, making it more polar and stable.

Answer

Resonance is a phenomenon unique to small, cyclic molecules like benzene.

Question 57

Which process combines light atomic nuclei, releasing significant energy?

Accepted Answer

Nuclear fusion

Answer

Nuclear fission

Answer

Combustion

Question 58

In modern society, chemicals and chemical reactions are widely used. What ethical considerations and potential risks should be taken into account?

Accepted Answer

Ethical considerations and risk management are essential for responsible chemical use.

Answer

Ethical issues are irrelevant in industrial chemical use.

Answer

Chemical reactions should be avoided due to their inherent risks.

Answer

The benefits of chemical use outweigh any ethical or environmental concerns.

Question 59

According to collision theory, which factors directly affect the speed of a chemical reaction?

Accepted Answer

Temperature and concentration

Answer

Activation energy

Answer

Surface area of reactants

Answer

Only the concentration of the reactants

Question 60

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

Accepted Answer

The total mass of the reactants is always greater than the total mass of the products.

Answer

The formation of new substances with different properties.

Answer

The rearrangement of atoms.

Question 61

What type of reaction is represented by the following equation: AB → A + B?

Accepted Answer

Decomposition

Answer

Single displacement

Answer

Synthesis

Question 62

Which of the following is an example of a single displacement reaction?

Accepted Answer

Zn + CuSO₄ → ZnSO₄ + Cu

Answer

NaOH + HCl → NaCl + H₂O

Answer

CaCO₃ → CaO + CO₂

Answer

2H₂ + O₂ → 2H₂O

Question 63

In a chemical reaction, the limiting reactant is the one that...

Accepted Answer

is completely consumed first, determining the amount of product formed.

Answer

has the lowest molar mass.

Answer

is present in the largest amount.

Question 64

What is the theoretical yield of a reaction if 10 grams of reactant A completely react with reactant B to produce 15 grams of product C?

Accepted Answer

15 grams

Answer

5 grams

Answer

10 grams

Answer

25 grams