Chemical Reactions and Stoichiometry Quiz
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Questions and Answers

What are the reactants in a chemical reaction?

  • The evidence of a reaction
  • The new substances formed
  • The heat absorbed or released
  • The substances that undergo a change (correct)

    • Which of the following is NOT a type of physical evidence indicating a chemical reaction has occurred?

  • Formation of a gas
  • Dissolution in water (correct)
  • Formation of a solid
  • Color change

    • Which statement best describes stoichiometry?

  • The study of temperature changes in reactions
  • The examination of quantities in chemical reactions (correct)
  • The observation of physical state changes
  • The measurement of reaction rates

    • According to the Law of Conservation of Mass, what remains constant during a chemical reaction?

    <p>The total mass of matter</p> Signup and view all the answers

    In a balanced chemical equation, what does the term 'coefficients' refer to?

    <p>The numbers of molecules of each reactant and product</p> Signup and view all the answers

    What is necessary for a chemical reaction to occur?

    <p>Evidence such as a color change</p> Signup and view all the answers

    How does one balance a chemical equation?

    <p>By changing the coefficients of reactants and products</p> Signup and view all the answers

    What separates the reactants from the products in a chemical equation?

    <p>An arrow (→)</p> Signup and view all the answers

    What occurs in a decomposition reaction?

    <p>A single substance breaks down into two or more different substances.</p> Signup and view all the answers

    In a single displacement reaction, what is exchanged?

    <p>Ions between two compounds.</p> Signup and view all the answers

    What distinguishes a double displacement reaction?

    <p>The positive and negative ions in the two compounds switch places.</p> Signup and view all the answers

    What is a common product of combustion reactions?

    <p>Water and carbon dioxide</p> Signup and view all the answers

    Which of the following represents a single displacement reaction?

    <p>Fe + CuSO4 ⟶ Cu + FeSO4</p> Signup and view all the answers

    What is the result when less reactive elements attempt to displace ions in a reaction?

    <p>No reaction occurs.</p> Signup and view all the answers

    Which of the following is a characteristic feature of a synthesis reaction?

    <p>It forms a single product from multiple reactants.</p> Signup and view all the answers

    In the reaction 2H2O2 ⟶ 2H2O + O2, what type of reaction does this illustrate?

    <p>Decomposition</p> Signup and view all the answers

    What is the formula weight of sucrose (C12H22O11)?

    <p>342.297 amu</p> Signup and view all the answers

    Which element has the highest percent mass composition in sucrose?

    <p>Carbon</p> Signup and view all the answers

    What is the percentage of oxygen by mass in sucrose?

    <p>51.41%</p> Signup and view all the answers

    Which calculation method is used to find the percent mass composition of an element in a compound?

    <p>(Number of atoms)(Atomic weight) / Formula weight of compound</p> Signup and view all the answers

    In the calculation of mass composition for H2SO4, what percentage of sulfur is found?

    <p>32.69%</p> Signup and view all the answers

    What is the percent mass composition of hydrogen in sucrose?

    <p>6.479%</p> Signup and view all the answers

    Why do we often not work with individual molecules in the lab?

    <p>They are too small</p> Signup and view all the answers

    In the formula for calculating percent mass composition, what does FW represent?

    <p>Formula weight</p> Signup and view all the answers

    What is the molar mass of carbon dioxide (CO2)?

    <p>44.009 g/mol</p> Signup and view all the answers

    How is the mass of oxygen (O) calculated from the sample?

    <p>mass of O = mass of the sample – (mass of C + mass of H)</p> Signup and view all the answers

    What is the empirical formula derived from the sample calculations?

    <p>C2H4O</p> Signup and view all the answers

    What should be the next step after determining the empirical formula?

    <p>Calculate the molar mass of the empirical formula.</p> Signup and view all the answers

    If the empirical formula of a compound is C2H4O and the molar mass is 156 g/mol, what is its molecular formula?

    <p>C4H8O2</p> Signup and view all the answers

    During the combustion of menthol, which of the following products is formed?

    <p>CO2 and H2O</p> Signup and view all the answers

    What is the final mass of oxygen in the menthol sample if combusted producing specified CO2 and H2O?

    <p>0.800 g</p> Signup and view all the answers

    What is the limiting reactant when 3.0 mol of N2 and 6.0 mol of H2 are used in the reaction to form ammonia?

    <p>H2</p> Signup and view all the answers

    What happens when there is an excess of a reactant in a chemical reaction?

    <p>It remains unreacted after the reaction.</p> Signup and view all the answers

    Why do power plants operate with an excess of O2(g)?

    <p>To minimize harmful byproducts.</p> Signup and view all the answers

    In the calculation of how much CaH2 is needed, what must you first determine?

    <p>The limiting reactant.</p> Signup and view all the answers

    What is the role of a limiting reactant in a chemical reaction?

    <p>It determines the amount of product formed.</p> Signup and view all the answers

    Study Notes

    Chemical Reactions

    • A chemical reaction transforms reactants into products, indicating a chemical change.
    • Evidence of a reaction includes:
      • Color change
      • Formation of a precipitate
      • Gas production
      • Heat evolution or absorption

    Stoichiometry

    • Studies the quantities of substances in chemical reactions.
    • Based on the Law of Conservation of Mass, asserting that mass is conserved during reactions.

    Chemical Equations

    • Represent chemical reactions using symbols and formulas; reactants on the left, products on the right.
    • Balancing equations requires adjusting coefficients (the numbers before substances), not subscripts (the numbers in formulas).
    • Follow the conservation of mass to ensure equal numbers of each atom on both sides.

    Decomposition Reactions

    • Break a compound into two or more simpler substances.
    • General formula: AB ⟶ A + B.
    • Example: 2H2O2 ⟶ 2H2O + O2 (decomposition of hydrogen peroxide).

    Single Displacement Reactions

    • An element reacts with a compound, replacing one of its components.
    • General formula can involve cation or anion exchange:
      • Cation: A + BC ⟶ B + AC
      • Anion: A + BC ⟶ C + BA.
    • Reactivity series determines if one element can replace another.

    Activity Series

    • More reactive elements can replace less reactive ones in reactions.
    • Example of cation exchange: Fe + CuSO4 ⟶ Cu + FeSO4.
    • Example of anion exchange: Cl2 + 2NaBr ⟶ 2NaCl + Br2.
    • Less reactive elements do not displace others; e.g., I2 + 2KBr ⟶ No Reaction.

    Double Displacement Reactions

    • Occurs when positive and negative ions in two compounds switch places.
    • General formula: AB + CD ⟶ AD + CB.
    • Examples include neutralization reactions like HCl + NaOH ⟶ NaCl + H2O.

    Combustion Reactions

    • A substance reacts with oxygen, releasing energy and producing CO2 and H2O.
    • General formula: CxHy + O2 ⟶ CO2 + H2O.
    • Examples include cellular respiration and methane combustion.

    Types of Chemical Reactions

    • Combination/Synthesis: A + B → AB.
    • Analysis/Decomposition: AB → A + B.
    • Single Displacement: A + BC → AC + B.
    • Double Displacement: AB + CD → AD + CB.

    Mass Composition Calculations

    • Percentage mass composition formula:
      • % mass = (number of atoms x atomic weight) / formula weight of compound x 100%.
    • Example: In H2SO4, %H = 2.056%, %S = 32.69%, %O = 65.25%.

    The Mole and Avogadro’s Number

    • Used to calculate amounts in stoichiometric relationships.
    • Example of determining the mass of carbon from the combustion of CO2.

    Limiting and Excess Reactants

    • The limiting reactant is present in the smallest amount and determines the extent of the reaction.
    • Example: In the formation of ammonia (NH3) from N2 and H2, the limiting reactant can be found by calculating the required moles based on the stoichiometry of the reaction.

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    Description

    Test your knowledge on key concepts of chemical reactions, stoichiometry, and chemical equations. This quiz covers evidence of reactions, balancing equations, and types of reactions including decomposition and single displacement. Challenge yourself and see how well you understand these fundamental chemistry topics!

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