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Quizzes > Science

Decomposition Reaction Quiz: Which Feature Identifies It?

Quick chemical reactions quiz to check your understanding. Instant results.

Editorial: Review CompletedCreated By: Alex McfallerUpdated Aug 25, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
paper art quiz illustration with chemistry glassware molecules testing reaction skills on a golden yellow background.

This quiz helps you spot the key feature of a decomposition reaction and practice classifying reaction types. For mixed practice on synthesis, single replacement, and more, try the types of reactions quick check, and review changes in matter with the physical vs chemical change quiz.

Which type of reaction involves two or more reactants combining to form a single product?
Double replacement reaction
Single replacement reaction
Synthesis reaction
Decomposition reaction
A synthesis reaction, also known as a combination reaction, occurs when two or more reactants form a single product. These reactions follow the general equation A + B ? AB and are commonly used in industrial processes to produce compounds. This type of reaction contrasts with decomposition and replacement reactions, which break down compounds or swap elements, respectively. For more details see .
What type of reaction is represented by the equation 2KClO3 ? 2KCl + 3O2?
Single replacement reaction
Synthesis reaction
Combustion reaction
Decomposition reaction
This equation shows a single reactant breaking down into multiple products, which defines a decomposition reaction. Such reactions often require energy input, like heat or a catalyst, to proceed. Decomposition of potassium chlorate is commonly used to generate oxygen in laboratory settings. See for further reading.
Which reaction type produces an insoluble solid when two aqueous solutions are mixed?
Acid-base neutralization
Redox reaction
Hydrolysis reaction
Precipitation reaction
A precipitation reaction forms an insoluble solid (precipitate) when two soluble reactants in aqueous solutions combine. The general form is AB(aq) + CD(aq) ? AD(s) + CB(aq). Precipitation reactions are used in analytical chemistry to identify ions in solution. More information at .
What distinguishes an exothermic reaction from an endothermic reaction?
Exothermic reactions always form a precipitate
Exothermic reactions change the pH of a solution
Exothermic reactions absorb heat from the surroundings
Exothermic reactions release heat to the surroundings
Exothermic reactions release energy, usually in the form of heat, to the surroundings and result in a temperature increase. In contrast, endothermic reactions absorb energy, causing the surroundings to feel colder. This distinction is important in thermochemistry and is described by enthalpy changes (?H). For details, visit .
Which of the following is an example of a single replacement reaction?
CaCO3 ? CaO + CO2
Na2SO4 + BaCl2 ? BaSO4 + 2NaCl
H2 + Cl2 ? 2HCl
Zn + 2HCl ? ZnCl2 + H2
In a single replacement reaction, one element replaces another in a compound, as zinc (Zn) replaces hydrogen in hydrochloric acid to form zinc chloride and hydrogen gas. This reaction follows the general form A + BC ? AC + B. It differs from synthesis, decomposition, and double replacement reactions. More on this at .
What type of reaction occurs when CH4 burns in oxygen to produce CO2 and H2O?
Synthesis reaction
Redox reaction
Combustion reaction
Decomposition reaction
A combustion reaction involves a substance reacting rapidly with oxygen to produce energy, carbon dioxide, and water, as shown by CH4 + 2O2 ? CO2 + 2H2O. Combustion reactions are both redox processes and energy-releasing. They are widely studied in both theory and practical applications like fuel combustion. For more, see .
Which of the following best describes a catalyst in a chemical reaction?
Shifts the equilibrium constant
Increases the temperature of the reaction
Speeds up the reaction without being consumed
Is consumed to form the product
A catalyst provides an alternative pathway with lower activation energy, increasing the reaction rate without being consumed. Catalysts do not alter the equilibrium position but help the system reach equilibrium faster. They are essential in many industrial and biological processes. Read more at .
According to the law of conservation of mass, during a chemical reaction:
The mass of the reactants equals the mass of the products
The total mass decreases
The total mass increases
Mass is not conserved if gases are released
The law of conservation of mass states that mass is neither created nor destroyed during a chemical reaction, so the total mass of reactants must equal the total mass of products. This principle is fundamental in balancing chemical equations. Any discrepancy usually arises from measurement error or unaccounted gases. More information is available at .
In the reaction 3H2 + O2 ? 2H2O, if you start with 3 moles of H2 and 1 mole of O2, which reagent is the limiting reagent?
Hydrogen (H2)
There is no limiting reagent
Water (H2O)
Oxygen (O2)
The stoichiometry requires 3 moles of H2 for each mole of O2 to produce water. With 3 moles of H2 and 1 mole of O2, oxygen is fully consumed first, making it the limiting reagent. The limiting reagent dictates the maximum product formation. More on limiting reagents at .
Which reagent determines the maximum amount of product formed in a chemical reaction?
Solvent
Limiting reagent
Excess reagent
Catalyst
The limiting reagent is completely consumed first during a chemical reaction and thus limits the amount of product formed. Excess reagents remain after the reaction is complete. Identifying the limiting reagent is critical for calculating theoretical yield. For details see .
Which test identifies the presence of carbonate ions in a solution?
Addition of silver nitrate producing a white precipitate
Addition of dilute acid resulting in effervescence
Flame test showing green color
Addition of barium chloride producing a white precipitate
Carbonate ions react with acids like HCl to produce CO2 gas, observed as effervescence (bubbling). This is a classic qualitative test for carbonates. Silver nitrate and barium chloride test for halides and sulfates, respectively. More on qualitative analysis at .
According to collision theory, which factor does NOT affect the rate of a chemical reaction?
Total mass of reactants
Frequency of collisions
Energy of collisions
Orientation of collisions
Collision theory states that reaction rate depends on collision frequency, orientation, and sufficient energy, but not on the total mass of reactants. Mass is related to the number of particles but is not a direct factor in collision efficiency. More on collision theory at .
Which term describes the minimum energy that reacting molecules must have to form products?
Potential energy
Activation energy
Binding energy
Lattice energy
Activation energy is the minimum energy barrier that reactant molecules must overcome for a reaction to proceed. It determines the reaction rate and is lowered by catalysts. This concept is central to understanding reaction kinetics. See for more.
In the rate law Rate = k[A]^2[B], what is the overall order of the reaction?
3
2
4
1
The overall reaction order is the sum of the exponents in the rate law, here 2 (for A) + 1 (for B) = 3. The reaction order impacts how rate responds to concentration changes. Rate laws are determined experimentally. More at .
What is the effect on the rate of a first-order reaction when the reactant concentration is doubled?
The rate quadruples
The rate halves
The rate doubles
The rate remains unchanged
For first-order reactions, the rate is directly proportional to reactant concentration. Doubling the concentration doubles the rate. This relationship follows Rate = k[A]^1. For more detail see .
Which characteristic describes a second-order reaction with respect to concentration and half-life?
Half-life is independent of concentration
Half-life is equal to the reaction rate constant
Half-life increases linearly with concentration
Half-life is inversely proportional to initial concentration
For a second-order reaction, the half-life (t1/2) depends on the initial concentration according to t1/2 = 1/(k[A]0). Thus, as initial concentration increases, the half-life decreases. This contrasts with first-order reactions. Read more at .
According to Hess's law, how does the total enthalpy change of a reaction relate to its reaction pathway?
It is independent of the pathway taken
It changes with temperature only
It depends on the pathway taken
It applies only under constant pressure
Hess's law states that the total enthalpy change for a reaction is the same regardless of the number of steps or the pathway taken, because enthalpy is a state function. This allows indirect calorimetry methods to calculate enthalpies for complex reactions. More at .
What is the relationship between standard Gibbs free energy change (?G°) and the equilibrium constant (K)?
?G° = K + RT
?G° = RT ln K
?G° = -K/RT
?G° = -RT ln K
The equation ?G° = -RT ln K links thermodynamics and equilibrium, where R is the gas constant and T is temperature. A negative ?G° indicates K > 1 and products are favored. This relationship is fundamental in predicting reaction spontaneity. Further info at .
Which change will shift the equilibrium of an endothermic reaction toward the products?
Decreasing the temperature
Increasing the temperature
Adding more products
Removing some reactants
For endothermic reactions (heat absorbed), raising the temperature adds heat, which Le Chatelier's principle predicts will shift the equilibrium toward the products. Conversely, lowering temperature favors reactants. More on equilibrium shifts at .
In an electrochemical cell, which electrode is the site of oxidation?
Electrolyte
Cathode
Anode
Salt bridge
Oxidation occurs at the anode, where electrons are lost. In galvanic cells, the anode is negative because it donates electrons, while the cathode receives electrons and is positive. This concept is key in electrochemistry. See .
According to Faraday's first law of electrolysis, the mass of substance deposited at an electrode is:
Inversely proportional to the quantity of electricity passed
Directly proportional to the quantity of electricity passed
Independent of current
Dependent only on electrode potential
Faraday's first law states that the mass of a substance altered at an electrode during electrolysis is directly proportional to the total electric charge passed through the circuit. This forms the basis for quantitative electrochemical analysis. More details at .
What is the oxidation state of sulfur in H2SO4?
+2
-2
+4
+6
In H2SO4, hydrogen has an oxidation state of +1 and oxygen -2. Summing 2(+1) + S + 4(-2) = 0 gives S = +6. Determining oxidation states is crucial in redox chemistry. For more, see .
What is a transition state in the context of reaction kinetics?
The final arrangement of products
A stable intermediate compound
A high-energy, unstable arrangement of atoms during a reaction
The reactant molecule before collision
The transition state is the highest energy point along the reaction path, representing an unstable arrangement of atoms as old bonds break and new ones form. It is not an isolated species and exists only momentarily. Activation energy corresponds to the energy needed to reach this state. Learn more at .
Which species acts as a spectator ion in the reaction between HCl and NaOH?
Na+
OH-
Cl-
H+
In the neutralization reaction HCl + NaOH ? NaCl + H2O, the sodium ion (Na+) remains unchanged in solution and does not participate in the acid-base reaction. Chloride, H+, and OH- are directly involved in forming water. Spectator ions are common in ionic reactions. See .
Which equation is used to calculate the cell potential of an electrochemical cell under nonstandard conditions?
Michaelis-Menten equation
Henderson-Hasselbalch equation
Arrhenius equation
Nernst equation
The Nernst equation, E = E° - (RT/nF) ln Q, relates cell potential to standard potential, temperature, reaction quotient Q, and the number of electrons transferred. It is fundamental for predicting cell behavior under nonstandard conditions. More details at .
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Study Outcomes

  1. Identify Reaction Types -

    List and recognize common chemical reaction types such as synthesis, decomposition, single and double replacement, and combustion when presented with reagents and products.

  2. Differentiate Reaction Categories -

    Distinguish between reaction classes by analyzing reactant and product patterns, enabling quick categorization during the chemical reaction exam.

  3. Analyze Chemical Equations -

    Interpret balanced chemical equations to determine the reaction type and understand the underlying stoichiometric relationships.

  4. Apply Reaction Tests -

    Use diagnostic methods like flame tests, precipitate formation, and gas evolution to confirm reaction occurrence and identify products.

  5. Predict Reaction Products -

    Anticipate likely products from given reactants and classify the resulting reaction type to reinforce predictive skills.

  6. Identify Knowledge Gaps -

    Assess strengths and uncover areas for review by analyzing quiz results, guiding targeted study before the exam.

Cheat Sheet

  1. Master the Six Major Reaction Types -

    University courses (e.g., MIT OpenCourseWare) categorize reactions into synthesis, decomposition, single-replacement, double-replacement, combustion, and acid - base neutralization. Use the mnemonic "S D SR DR C AB" to recall each type quickly for your chemical reaction exam. Writing one balanced equation per category will boost retention and prep you for any types of reactions quiz.

  2. Balance Equations with Systematic Steps -

    Balancing obeys the law of conservation of mass: atoms in = atoms out. Follow a methodical approach - start with metals, then nonmetals, finish with hydrogen and oxygen - to avoid trial and error (University of California guidelines). Mastery here is key for high scores on any quiz on types of chemical reactions or chemical reactions test.

  3. Understand Energetics: Exothermic vs. Endothermic -

    Reaction enthalpy (ΔH) tells you if energy is released (exothermic, ΔH<0) or absorbed (endothermic, ΔH>0); see data tables from NIST. Visualize energy profiles with activation energy peaks to predict reaction spontaneity. This concept often appears in chemical reaction exam questions about heat flow and equilibrium.

  4. Apply Collision Theory to Reaction Rates -

    According to collision theory (Royal Society of Chemistry), rate depends on frequency of effective collisions with proper orientation and energy. Factors like temperature, concentration, surface area, and catalysts all influence rate constants (k) in the rate law. Correlate these factors with real-world scenarios to ace your quiz chemical reactions section.

  5. Practice Common Reaction Tests -

    Identify products with tests like flame tests for metal ions, precipitation reactions for halides, and redox titrations (e.g., KMnO₄). pH indicators and conductivity measurements further confirm acid - base and ionic reactions (American Chemical Society resources). Hands-on familiarity ensures confidence when tackling a chemical reactions test or quiz on types of chemical reactions.

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