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Quizzes > Science > Chemistry

Take the Chemical Reactions Quiz and Ace Balancing Equations

Ready for a chemistry quiz? Dive into balancing equations and formula practice now!

Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
paper art flasks test tubes molecular structures chemical equations on teal background for chemical reactions quiz

This Chemical Reactions Quiz helps you balance equations, spot reaction types, and write correct formulas, with extra equation practice if you want. You get instant feedback on practice questions so you can check gaps before an exam or sharpen skills fast.

In the reaction H2 + O2 -> H2O, what is the coefficient for O2 when the equation is balanced?
4
3
1
2
Balancing the reaction requires two hydrogen molecules and one oxygen molecule to produce two water molecules, giving 2H2 + O2 -> 2H2O. The coefficient for O2 is thus 1. This ensures both hydrogen and oxygen atoms are balanced on each side.
What type of reaction is represented by CH4 + 2O2 -> CO2 + 2H2O?
Synthesis
Decomposition
Single Replacement
Combustion
A combustion reaction involves a hydrocarbon reacting with oxygen to produce carbon dioxide and water. Combustion is exothermic and requires O2 as a reactant. The products CO2 and H2O are characteristic of complete combustion of methane.
What type of reaction is Zn + 2HCl -> ZnCl2 + H2?
Single Replacement
Combustion
Double Replacement
Synthesis
In a single replacement reaction, an element replaces another element in a compound. Here, zinc metal replaces the hydrogen in HCl to form ZnCl2 and hydrogen gas. Only one element and one compound are on the reactant side, characteristic of single replacement.
What is the chemical formula for magnesium chloride?
MgCl4
Mg2Cl
MgCl
MgCl2
Magnesium forms a +2 cation (Mg2+) and chlorine forms a - 1 anion (Cl - ). Two chloride ions are needed to balance one magnesium ion, giving the formula MgCl2. This follows the rules for ionic compound formation.
In the reaction N2 + H2 -> NH3, what is the coefficient for H2 when the equation is balanced?
2
4
1
3
Balancing N2 + H2 -> NH3 requires 3 molecules of H2 to give 6 hydrogen atoms for making 2 molecules of NH3. The balanced equation is N2 + 3H2 -> 2NH3. Thus, the coefficient for H2 is 3.
What is the net ionic equation for the formation of AgCl precipitate from AgNO3 and NaCl?
AgNO3 + NaCl -> AgCl + NaNO3
Ag+ + NO3- -> AgCl
Ag+ + Cl- -> AgCl
Na+ + Cl- -> NaCl
The net ionic equation shows only the species that change during precipitation. Silver ions combine with chloride ions to form solid AgCl, omitting spectator ions. Therefore, Ag+ + Cl- -> AgCl is correct.
What type of reaction is 2Na + Cl2 -> 2NaCl?
Combustion
Synthesis
Decomposition
Single Replacement
Synthesis (or combination) reactions combine two or more reactants to form a single product. Here, sodium and chlorine gas combine to form sodium chloride. This is a classic synthesis reaction.
In the reaction Zn + Cu2+ -> Zn2+ + Cu, which element is oxidized?
O2
Zn
Cu
Cl2
Oxidation is the loss of electrons. Zinc goes from 0 to +2 oxidation state, losing electrons, so Zn is oxidized. Copper ions gain those electrons to become Cu(0), so Cu is reduced.
What is the coefficient for Fe when balancing the equation Fe + O2 -> Fe2O3 as 4Fe + 3O2 -> 2Fe2O3?
2
1
3
4
To balance Fe + O2 -> Fe2O3, you need 4 iron atoms to match the two Fe2O3 units (each with two iron atoms). The balanced equation is 4Fe + 3O2 -> 2Fe2O3. Thus, the coefficient for Fe is 4.
What type of reaction is represented by 2KClO3 -> 2KCl + 3O2?
Double Replacement
Synthesis
Combustion
Decomposition
A decomposition reaction involves a single compound breaking down into two or more simpler substances. Potassium chlorate decomposes into potassium chloride and oxygen gas. This is a thermal decomposition when heated.
What is the chemical formula for barium sulfate?
BaSO4
BSO4
Ba2(SO4)
BaS
Barium forms a +2 cation (Ba2+) and sulfate is a -2 anion (SO4^2 - ). They combine in a 1:1 ratio, giving the neutral compound BaSO4. This salt is insoluble in water.
In the combustion reaction C3H8 + O2 -> CO2 + H2O, what is the coefficient for O2 when the equation is balanced?
5
4
6
3
Propane combustion balances as C3H8 + 5O2 -> 3CO2 + 4H2O. Five molecules of dioxygen provide the necessary oxygen atoms for three CO2 and four H2O molecules. Thus, the coefficient for O2 is 5.
What type of reaction is H2SO4 + 2NaOH -> Na2SO4 + 2H2O?
Combustion
Decomposition
Neutralization
Synthesis
Neutralization reactions occur when an acid reacts with a base to form salt and water. Sulfuric acid neutralizes sodium hydroxide to yield sodium sulfate and water. This is a specific type of double replacement reaction.
What is the net ionic equation for the reaction between HCl and NaOH?
Cl- + Na+ -> NaCl
H+ + OH- -> H2O
H+ + Cl- + Na+ + OH- -> Na+ + Cl- + H2O
HCl + NaOH -> NaCl + H2O
The net ionic equation for an acid-base neutralization shows only hydrogen ions reacting with hydroxide ions to form water. Spectator ions (Na+ and Cl - ) are omitted. Hence H+ + OH - -> H2O is correct.
What is the oxidation state of sulfur in H2SO4?
+1
+6
+2
+4
Assigning oxidation states in H2SO4, hydrogen is +1 (two H give +2 total) and oxygen is -2 (four O give -8). To balance, sulfur must be +6. Sulfur's +6 oxidation state is common in sulfate.
When balancing Al + HCl -> AlCl3 + H2, what is the coefficient for HCl in the balanced equation?
4
2
3
6
Balancing Al + HCl -> AlCl3 + H2 gives 2Al + 6HCl -> 2AlCl3 + 3H2. Six molecules of HCl provide three chloride ions per aluminum atom. The coefficient for HCl is therefore 6.
In acidic solution, the redox reaction MnO4- + Fe2+ -> Mn2+ + Fe3+ is balanced as MnO4- + 5Fe2+ + 8H+ -> Mn2+ + 5Fe3+ + 4H2O. What is the coefficient for H+?
4
8
5
10
Balancing redox in acidic solution requires adding H+ to balance hydrogen and charge. The half-reactions combine to give 8H+ on the reactant side. Thus the coefficient for H+ is 8.
What type of reaction is CH3COOH + C2H5OH -> CH3COOC2H5 + H2O?
Oxidation
Precipitation
Hydrolysis
Esterification
Esterification is the reaction of a carboxylic acid with an alcohol to form an ester and water. Acetic acid and ethanol combine to produce ethyl acetate and water. This is typically acid-catalyzed.
What is the chemical formula for ammonium phosphate?
(NH4)3PO4
NH4(PO4)3
(NH4)2PO4
NH4PO4
Ammonium is NH4+ (charge +1) and phosphate is PO4^3 - (charge -3). Three ammonium ions balance one phosphate ion, yielding (NH4)3PO4. This ensures electrical neutrality.
Balance the reaction K2Cr2O7 + HCl -> KCl + CrCl3 + Cl2 + H2O. What is the coefficient for HCl?
21
7
10
14
The balanced redox reaction in acidic medium is K2Cr2O7 + 14HCl -> 2KCl + 2CrCl3 + 3Cl2 + 7H2O. Fourteen HCl molecules supply the necessary chloride and protons. The coefficient for HCl is 14.
What type of reaction is 2H2O2 -> 2H2O + O2?
Combustion
Decomposition
Single Replacement
Synthesis
Hydrogen peroxide breaks down into water and oxygen gas in a decomposition reaction. This occurs spontaneously or catalyzed by substances like manganese dioxide. It involves breaking a single reactant into multiple products.
In the reaction 2Na + 2H2O -> 2NaOH + H2, which species acts as the oxidizing agent?
Na
H2O
NaOH
H2
An oxidizing agent gains electrons and is reduced. Water is reduced to hydrogen gas (H2), gaining electrons from sodium. Sodium is oxidized, so water is the oxidizing agent.
When balancing P4 + O2 -> P2O5, what is the coefficient for O2?
5
2
10
4
The balanced equation is P4 + 5O2 -> 2P2O5. Five diatomic oxygen molecules provide the ten oxygen atoms needed for two molecules of P2O5. Thus the coefficient for O2 is 5.
What is the oxidation state of chromium in Cr2O7^2-?
+2
+6
+3
+4
In dichromate, each oxygen is -2 (7 O give -14). The overall charge is -2, so the total oxidation of two Cr atoms must be +12. Each chromium has an oxidation state of +6.
In basic solution, balance the redox reaction MnO4- + SO3^2- -> MnO2 + SO4^2-. What is the coefficient for OH- in the balanced equation 2MnO4- + 3SO3^2- + H2O -> 2MnO2 + 3SO4^2- + 2OH-?
1
4
2
3
Balancing redox in basic medium requires adding OH- to neutralize excess H+. After combining half-reactions, two OH- appear on the product side. Hence the coefficient for OH- is 2.
What type of reaction is represented by 3C + 2FeO -> Fe3O4 + 2CO?
Redox
Neutralization
Decomposition
Precipitation
This reaction involves electron transfer: carbon reduces iron(II) oxide to form magnetite (Fe3O4) and carbon monoxide. Both oxidation and reduction occur, defining it as a redox reaction. There is no formation of acids, bases, or precipitates.
0
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Study Outcomes

  1. Apply Balanced Equations -

    Use the law of conservation of mass to accurately balance chemical equations, ensuring reactant and product atom counts match.

  2. Identify Reaction Types -

    Classify chemical reactions into categories such as synthesis, decomposition, single replacement, double replacement, and combustion.

  3. Distinguish Physical vs Chemical Changes -

    Differentiate between physical and chemical changes by analyzing evidence of new substance formation and energy changes.

  4. Write Chemical Formulas -

    Construct correct chemical formulas for compounds and reactants using element symbols and oxidation states.

  5. Predict Reaction Products -

    Anticipate the products of common reaction types based on reactant information and reaction rules.

  6. Reinforce Problem-Solving Skills -

    Apply step-by-step strategies to tackle complex balance chemical equations quiz problems and improve speed and accuracy.

Cheat Sheet

  1. Law of Conservation of Mass -

    Every balanced chemical equation must obey the Law of Conservation of Mass, which states that atoms are neither created nor destroyed. For example, the combustion of hydrogen is balanced as 2H₂ + O₂ → 2H₂O, ensuring equal counts of H and O on both sides (source: MIT OpenCourseWare).

  2. Common Reaction Types -

    Recognize synthesis (A + B → AB), decomposition (AB → A + B), single”displacement (A + BC → AC + B), double”displacement (AB + CD → AD + CB), and combustion reactions. Identifying the pattern helps predict products quickly and is reinforced by practice quizzes on chemistry department websites like UC Berkeley's ChemWiki.

  3. Balancing Tips & Mnemonics -

    Use the inspection method: balance one element at a time, leaving pure elements for last. A handy mnemonic is "OIL RIG" (Oxidation Is Loss, Reduction Is Gain) to track electron shifts in redox reactions (reference: American Chemical Society).

  4. Physical vs Chemical Changes -

    Distinguish physical changes (e.g., melting ice) from chemical changes (e.g., rusting iron) by looking for new substance formation, color changes, or gas evolution. The mnemonic "CLAP" (Color, Loss/Gain of heat, Appearance of gas, Precipitate) can help you spot chemical changes (source: Royal Society of Chemistry).

  5. Writing Chemical Formulas -

    Combine element symbols and their valencies using the criss”cross method: swap charges to subscripts, then simplify. For instance, Al³❺ and SO₄²❻ give Al₂(SO₄)₃, a trick covered in depth by Khan Academy's formula tutorials.

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