Chemistry

Chemical Reactions and Equations

684 Questions

Chemical reactions and equations form a foundational chemistry topic where students identify reaction products, balance chemical formulas, and classify reaction types. It covers critical mechanisms like Markovnikov's rule, precipitation, and endothermic or exothermic processes. These questions are highly common in general science sections of state and central government competitive exams.

Endothermic reactionsPrecipitation reactionsDehydrohalogenation of alkyl halidesChemical equation balancingReaction product identification

Chemical Reactions and Equations Questions

Multiple choice

What is the chemical equation for the decomposition of water?

  1. $$2H_2O \rightarrow 2H_2 + O_2$$
  2. $$H_2O \rightarrow H_2 + OH^-$$
  3. $$2H_2O \rightarrow H_3O^+ + OH^-$$
  4. $$H_2O \rightarrow H^+ + OH^-$$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The chemical equation for the decomposition of water is $$2H_2O \rightarrow 2H_2 + O_2$$. This reaction is a decomposition reaction in which water breaks down into hydrogen and oxygen.

Multiple choice

What is the chemical equation for the single-replacement reaction between zinc and copper sulfate?

  1. $$Zn + CuSO_4 \rightarrow ZnSO_4 + Cu$$
  2. $$Zn + CuSO_4 \rightarrow ZnCu + SO_4^{2-}$$
  3. $$Zn + CuSO_4 \rightarrow ZnS + CuO$$
  4. $$Zn + CuSO_4 \rightarrow Zn(OH)_2 + CuSO_3$$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The chemical equation for the single-replacement reaction between zinc and copper sulfate is $$Zn + CuSO_4 \rightarrow ZnSO_4 + Cu$$. In this reaction, zinc replaces copper in copper sulfate to form zinc sulfate and copper.

Multiple choice

What is the chemical equation for the double-replacement reaction between sodium chloride and silver nitrate?

  1. $$NaCl + AgNO_3 \rightarrow NaNO_3 + AgCl$$
  2. $$NaCl + AgNO_3 \rightarrow NaAg + NO_3^-$$
  3. $$NaCl + AgNO_3 \rightarrow NaClO_3 + AgNO_2$$
  4. $$NaCl + AgNO_3 \rightarrow Na(OH) + AgCl$$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The chemical equation for the double-replacement reaction between sodium chloride and silver nitrate is $$NaCl + AgNO_3 \rightarrow NaNO_3 + AgCl$$. In this reaction, the cations of sodium and silver switch places to form sodium nitrate and silver chloride.

Multiple choice

What is the chemical equation for the decomposition of hydrogen peroxide?

  1. $$2H_2O_2 \rightarrow 2H_2O + O_2$$
  2. $$H_2O_2 \rightarrow H_2 + O_2$$
  3. $$2H_2O_2 \rightarrow H_2O + O$$
  4. $$H_2O_2 \rightarrow H^+ + OH^-$$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The chemical equation for the decomposition of hydrogen peroxide is $$2H_2O_2 \rightarrow 2H_2O + O_2$$. This reaction is a decomposition reaction in which hydrogen peroxide breaks down into water and oxygen.

Multiple choice

What is the chemical equation for the single-replacement reaction between magnesium and hydrochloric acid?

  1. $$Mg + HCl \rightarrow MgCl_2 + H_2$$
  2. $$Mg + HCl \rightarrow MgH_2 + Cl_2$$
  3. $$Mg + HCl \rightarrow MgO + H_2$$
  4. $$Mg + HCl \rightarrow Mg(OH)_2 + Cl_2$$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The chemical equation for the single-replacement reaction between magnesium and hydrochloric acid is $$Mg + HCl \rightarrow MgCl_2 + H_2$$. In this reaction, magnesium replaces hydrogen in hydrochloric acid to form magnesium chloride and hydrogen.

Multiple choice

What is the chemical equation for the double-replacement reaction between sodium hydroxide and sulfuric acid?

  1. $$NaOH + H_2SO_4 \rightarrow Na_2SO_4 + H_2O$$
  2. $$NaOH + H_2SO_4 \rightarrow NaHSO_4 + H_2O$$
  3. $$NaOH + H_2SO_4 \rightarrow Na_2S + H_2O$$
  4. $$NaOH + H_2SO_4 \rightarrow Na(OH)_2 + SO_2$$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The chemical equation for the double-replacement reaction between sodium hydroxide and sulfuric acid is $$NaOH + H_2SO_4 \rightarrow Na_2SO_4 + H_2O$$. In this reaction, the cations of sodium and hydrogen switch places to form sodium sulfate and water.

Multiple choice

Which of the following reactions is an example of a homogeneous equilibrium?

  1. CaCO3(s) <=> CaO(s) + CO2(g)

  2. H2(g) + Cl2(g) <=> 2HCl(g)

  3. Fe(s) + CuSO4(aq) <=> FeSO4(aq) + Cu(s)

  4. CH3COOH(aq) + H2O(l) <=> CH3COO-(aq) + H3O+(aq)
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A homogeneous equilibrium is a reaction in which all of the reactants and products are in the same phase. In the reaction H2(g) + Cl2(g) <=> 2HCl(g), all of the reactants and products are gases.

Multiple choice

Which of the following reactions is an example of a heterogeneous equilibrium?

  1. CaCO3(s) <=> CaO(s) + CO2(g)

  2. H2(g) + Cl2(g) <=> 2HCl(g)

  3. Fe(s) + CuSO4(aq) <=> FeSO4(aq) + Cu(s)

  4. CH3COOH(aq) + H2O(l) <=> CH3COO-(aq) + H3O+(aq)
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A heterogeneous equilibrium is a reaction in which the reactants and products are in different phases. In the reaction CaCO3(s) <=> CaO(s) + CO2(g), the reactants are in the solid phase and the product is in the gas phase.

Multiple choice

What is the balanced chemical equation for the combustion of methane?

  1. CH₄ + 2O₂ → CO₂ + 2H₂O

  2. CH₄ + O₂ → CO + 2H₂

  3. CH₄ + 2O₂ → CO₂ + H₂O

  4. CH₄ + O₂ → C + 2H₂O
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The balanced chemical equation for the combustion of methane is CH₄ + 2O₂ → CO₂ + 2H₂O. This equation shows that one molecule of methane reacts with two molecules of oxygen to produce one molecule of carbon dioxide and two molecules of water.

Multiple choice

Which of the following is an example of a homogeneous AOP?

  1. Ozonation

  2. Hydrogen Peroxide/UV

  3. Fenton Process

  4. Heterogeneous Photocatalysis
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The Fenton Process is an example of a homogeneous AOP as the reactants (ferrous iron and hydrogen peroxide) are uniformly distributed throughout the water.

Multiple choice

Which of the following is an example of a heterogeneous AOP?

  1. Ozonation

  2. Hydrogen Peroxide/UV

  3. Fenton Process

  4. Heterogeneous Photocatalysis
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Heterogeneous photocatalysis, typically involving a semiconductor catalyst such as titanium dioxide (TiO2), is an example of a heterogeneous AOP.

Multiple choice

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

  1. Synthesis reaction

  2. Decomposition reaction

  3. Single-replacement reaction

  4. Double-replacement reaction
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Single-replacement reaction is a type of chemical reaction in which one element replaces another element in a compound.

Multiple choice

What is the term for the photochemical reaction in which two molecules combine to form a single molecule?

  1. Photodimerization

  2. Photocycloaddition

  3. Photopolymerization

  4. Photoaddition
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Photocycloaddition is the term for the photochemical reaction in which two molecules combine to form a single molecule, typically involving a [2+2] or [4+2] cycloaddition reaction.

Multiple choice

What is the term for the photochemical reaction in which a molecule undergoes oxidation?

  1. Photooxidation

  2. Photoreduction

  3. Photodissociation

  4. Photoionization
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Photooxidation is the term for the photochemical reaction in which a molecule undergoes oxidation, typically involving the transfer of electrons to an oxidizing agent.

Multiple choice

What is the overall reaction that takes place in a Zinc-Air battery during discharge?

  1. Zn + O2 → ZnO

  2. Zn + 2OH- → Zn(OH)2 + 2e-

  3. 2Zn + O2 → 2ZnO

  4. Zn + 2H2O → Zn(OH)2 + H2
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The overall reaction in a Zinc-Air battery during discharge is the combination of zinc and oxygen to form zinc oxide.