Types of Chemical Reactions
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Questions and Answers

What is the primary product of a synthesis reaction?

  • Heat and light
  • A new substance formed (correct)
  • Two or more products
  • Water and salt

    • Which of the following represents a decomposition reaction?

  • C H 4(g) + 2O2(g) → C O2(g) + 2H 2 O (l)
  • AgNO3(aq) + NaCl(aq) → NaNO3(aq) + AgCl(s)
  • AB → A + B (correct)
  • HCl(aq) + NaOH(s) → NaCl(aq) + H 2 O(l)

    • What is produced in a complete combustion reaction of methane?

  • Carbon monoxide and hydrogen
  • Only carbon dioxide
  • Carbon dioxide and water (correct)
  • Carbon and water

    • In a precipitation reaction, what happens when two soluble ionic compounds are mixed?

    <p>They can form an insoluble precipitate.</p> Signup and view all the answers

    What is the purpose of the salt bridge in a galvanic cell?

    <p>To maintain solution neutrality and complete the circuit.</p> Signup and view all the answers

    Which of the following correctly describes the net ionic equation presented?

    <p>It only shows the ions that participate in the formation of the product.</p> Signup and view all the answers

    Which of the following reactions identifies acid-carbonate reactions?

    <p>Na2CO3(s) + 2HCl(aq) → 2NaCl(aq) + H2O(l) + CO2(g)</p> Signup and view all the answers

    What do metal-water reactions typically produce?

    <p>Metal hydroxide and hydrogen gas</p> Signup and view all the answers

    What happens at the anode of a galvanic cell?

    <p>Oxidation occurs producing free electrons.</p> Signup and view all the answers

    How can a reaction be represented as a complete ionic equation?

    <p>By showing all ions present during the reaction.</p> Signup and view all the answers

    In a metal displacement reaction, what determines which metal will displace another?

    <p>The metal activity series</p> Signup and view all the answers

    In the context of redox reactions, which statement is accurate about half equations?

    <p>They illustrate the transfer of electrons for either oxidation or reduction.</p> Signup and view all the answers

    What is the outcome of an acid-metal reaction?

    <p>A metal salt and hydrogen gas are formed.</p> Signup and view all the answers

    What governs the filling order of atomic orbitals?

    <p>The Aufbau principle</p> Signup and view all the answers

    Which principle explains that two identical fermions cannot occupy the same quantum state?

    <p>The Pauli exclusion principle</p> Signup and view all the answers

    What is the significance of the exceptions to the Aufbau principle in the d block?

    <p>They occur because of Coulombic repulsion and energy distinctions.</p> Signup and view all the answers

    What determines the variable valency of an atom?

    <p>The maximum number of direct bonds formable.</p> Signup and view all the answers

    What happens to electrons when they receive energy?

    <p>They can become excited and move to higher energy levels.</p> Signup and view all the answers

    Which group of elements consists of f orbitals?

    <p>Lanthanides and actinides</p> Signup and view all the answers

    What is the relationship between elements in the same group of the periodic table?

    <p>They have the same number of valence electrons.</p> Signup and view all the answers

    What occurs during the de-excitation of an electron?

    <p>Energy is released in the form of light.</p> Signup and view all the answers

    What does a higher value of reduction potential indicate?

    <p>Stronger tendency to form the non-ionic form</p> Signup and view all the answers

    Which component is reduced in a galvanic cell?

    <p>The oxidizing agent</p> Signup and view all the answers

    What is the effect of increasing temperature on the rate of reaction according to collision theory?

    <p>Increases the kinetic energy of particles</p> Signup and view all the answers

    In a galvanic cell notation, what does the left side represent?

    <p>Oxidation half-cell</p> Signup and view all the answers

    How is the voltage of a galvanic cell calculated?

    <p>E total = E reduction + E oxidation</p> Signup and view all the answers

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

    <p>Time of day</p> Signup and view all the answers

    What happens to the anode in a typical galvanic cell reaction involving zinc and copper?

    <p>It loses electrons and becomes smaller</p> Signup and view all the answers

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

    <p>It speeds up the rate of reaction without being used up</p> Signup and view all the answers

    What role do catalysts play in chemical reactions?

    <p>They provide an alternative pathway with lower activation energy.</p> Signup and view all the answers

    Which of the following statements about exothermic reactions is true?

    <p>Energy released in making bonds is greater than energy needed to break bonds.</p> Signup and view all the answers

    How is the change in enthalpy (ΔH) calculated?

    <p>ΔH = H products − H reactants</p> Signup and view all the answers

    Which substance is an example of a biological catalyst?

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

    What does specific heat capacity measure?

    <p>The amount of heat needed to raise 1g of a substance by 1°C</p> Signup and view all the answers

    What is true about endothermic reactions?

    <p>They absorb heat and cannot be self-sustaining.</p> Signup and view all the answers

    Which of the following calculations uses the correct formula for heat of combustion?

    <p>Energy released = n × ΔH c</p> Signup and view all the answers

    Which of the following is true about heterogeneous catalysts?

    <p>They differ in phase from the reactants.</p> Signup and view all the answers

    Study Notes

    Types of Reactions

    • Synthesis: Two or more substances combine to form a new substance. Example: A + B → AB
    • Decomposition: Substance breaks down into two or more substances due to heat, light or electricity. Example: AB → A + B
    • Acid-base (Neutralisation): Acid reacts with a base to form salt and water. Example: HCl(aq) + NaOH(s) → NaCl(aq) + H2O(l)
    • Combustion Reactions: Substances burn in oxygen.
      • Complete Combustion: Forms carbon dioxide and water. Example: CH4(g) + 2O2(g) → CO2(g) + 2H2O(l)
      • Incomplete Combustion: Forms carbon or carbon monoxide. Examples: CH4(g) + O2(g) → C(s) + 2H2O(l) and CH4(g) + 2/3O2(g) → CO(g) + 2H2O(l)
    • Precipitation Reactions (Double Displacement): Two soluble ionic compounds react to form an insoluble precipitate (ppt) or mix completely. Example: AB + CD → AD + CB
      • Precipitation Example: AgNO3(aq) + NaCl(aq) → NaNO3(aq) + AgCl(s)
    • Acid-carbonate reactions: Acid reacts with carbonate to form water, salt, and carbon dioxide. Example: Na2CO3(s) + 2HCl(aq) → 2NaCl(aq) + H2O(l) + CO2(g)
    • Metal - Oxygen Reactions: Metal burns in oxygen to form a metal oxide. Example: 2Mg(s) + O2(g) → 2MgO(s)
    • Metal - Water Reactions: Metal reacts with water to form a metal hydroxide and hydrogen gas. Example: 2Na(s) + 2H2O(l) → 2NaOH(s) + H2(g)
    • Acid-metal Reactions: Acid reacts with metal to form a metal salt and hydrogen gas. Example: Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g)
    • Metal Displacement Reactions: More reactive metal displaces a less reactive metal in a compound. Example: A + BC → AC + B
      • Displacement Example: Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s)
      • Metal reactivity determined by the metal activity series or reduction potentials table. Lower ionisation energy, larger atomic radius, and lower electronegativities indicate higher reactivity.

    Atomic Structure

    • Principal Energy Levels (1, 2, 3…): Groupings of sublevels (s, p, d, f) with similar energy.
    • Sublevels (s, p, d, f): Groupings of individual orbital lobes.
    • Aufbau Principle: Electrons fill lowest available energy levels first before occupying higher levels.
    • Exceptions to Aufbau Principle: Occur in the d block due to reduced energy difference between s and d levels, causing Coulombic repulsion. Examples: Cu, Ag, Cr.
    • Heisenberg Uncertainty Principle: The position and momentum of a particle (like an electron) cannot be measured accurately at the same time.
    • Pauli Exclusion Principle & Hund's Rule: Each orbital within an energy level is filled first by electrons with spin +1/2 and then completed with electrons of -1/2 spin (identical fermions cannot occupy the same quantum state within the same system). Example: Oxygen
    • Valence Electrons: Electrons in the outermost shell of an atom.
    • Valency: Maximum number of direct bonds that an element can form. Variable valency can occur when an atom loses or gains more electrons than its valence shell.
    • Orbital Notation: Determined by filling orbitals based on the number of electrons or using spdf blocks on the periodic table.
      • Helium and groups 1 and 2: s orbitals from energy levels 1-7
      • Transition metals: d orbitals from energy levels 3-6
      • Groups 13-18 (excluding Helium): p orbitals from energy levels 2-7
      • Lanthanides and Actinides: f orbitals from energy levels 4-5

    Atomic Emission Spectra and Flame Tests

    • Excitation: Electrons gain energy, move to a higher energy level.
    • De-excitation: Excited electrons return to their ground state, releasing energy as different wavelengths of light.

    Redox Reactions

    • Half-Equations: Show electron transfer.
    • Neutral Species Equations: Show compounds involved.
    • Complete Ionic Equation: Shows all ions in the reaction mixture.
    • Net Ionic Equation: Shows only the ions undergoing the reaction, excluding spectator ions.
    • Deriving Equations:
      1. Balanced Formula (Neutral Species) Equation: 2KI(aq) + Pb(NO2)3(aq) → PbI2(s) + 2KNO3(aq)
      2. Total Ionic Equation (Complete Ionic): 2K+(aq) + 2I-(aq) + Pb2+(aq) + 2NO3-(aq) → PbI2(s) + 2K+(aq) + 2NO3-(aq)
      3. Net Ionic Equation: Pb2+(aq) + 2I-(aq) → PbI2(s)

    Galvanic Cells and Standard Electrode Potentials

    • Galvanic Cells: Generate electricity via redox reactions.
      • Anode: Oxidation occurs, producing free electrons in the more reactive metal.
      • Cathode: Electrons flow to the cathode, resulting in reduction.
      • Salt Bridge: Completes the circuit, conserving solution neutrality.
        • Anions flow toward the anode to balance positive ions.
        • Cations flow toward the cathode to balance negative charges.
    • Standard Hydrogen Half-Cell: Platinum metal in a 1 mol/L H+ solution with hydrogen gas bubbled over at 100 kPa.
    • Standard Electrode Potentials: Higher values indicate a stronger tendency to form the non-ionic form; lower values suggest a tendency to form ions.
    • Voltage of a Galvanic Cell under Standard Conditions: Etotal = E°reduction + E°oxidation
      • Galvanic cells are spontaneous when cell voltage is positive.
      • Oxidizing agents are reduced, and vice versa.
    • Galvanic Cell Notation: X(s) | X+(aq) || Y+(aq) | Y(s) with the anode/oxidation on the left.
    • Galvanic Cell Example:
      • Copper gains electrons at the cathode.
      • Zinc loses electrons at the anode.
      • Notation for Zn(s) | Zn2+(aq)(1M) || Cu2+(aq)(1M) | Cu(s)

    Rates of Reactions

    • Collision Theory: Reactions occur due to collisions between reactant particles.
      • Requires:
        • Collisions between particles
        • Sufficient energy to break bonds and reach activation energy
        • Correct orientation to break bonds and form products
    • Activation Energy: Minimum energy required for a collision to lead to reaction.
    • Measuring Reaction Rates: Use time or loss of mass.
    • Factors Influencing Reaction Rates:
      • Surface Area: Higher surface area leads to more collisions.
      • Temperature: Higher temperature increases kinetic energy, increasing collision probability.
      • Concentration: Higher concentration means more particles, increasing collision probability.
      • Pressure (Gases): Higher pressure brings particles closer, increasing collision probability.
      • Presence of a Catalyst: Catalysts speed up reactions, but are not consumed. They provide an alternative pathway with lower activation energy.
      • Examples:
        • Iron (Fe) in ammonia production: N2(g) + 3H2(g) → 2NH3(g) ΔH = -92 kJ/mol
        • Platinum (Pt) in carbon monoxide to carbon dioxide: CO(g) + 1/2 O2(g) → CO2(g)
        • Potassium permanganate (KMnO4) in hydrogen peroxide decomposition: 2H2O2(aq) → 2H2O(l) + O2(g)
        • Chlorophyll in leaves for photosynthesis
      • Heterogeneous Catalysts: Different phase from reactants (e.g. gas - liquid)
      • Homogeneous Catalysts: Same phase as reactants (e.g. liquid - liquid)
      • Homogeneous Reactions: Occur in a single phase (e.g. liquid - liquid)

    Drivers of Reactions

    • Chemical Potential Energy: All substances hold chemical potential energy.
    • Bond Breaking: Requires energy.
    • Bond Making: Releases energy.
    • Exothermic Reactions: Release heat into the surroundings.
      • Energy released during bond making is greater than the energy needed to break bonds.
    • Endothermic Reactions: Absorb heat from the surroundings.
      • Energy required to break bonds is greater than the energy released during bond making.
    • Enthalpy: Total heat content of a system, measured in joules (J).
    • Change in Enthalpy (ΔH): ΔH = Hproducts - Hreactants where H is heat content.
    • Heat of Combustion (ΔHc): Energy released when 1 mol of a substance combusts completely at SLC.
      • Energy released for n moles of fuel burning: Energy released = n x ΔHc (when ΔHc is known)
    • Determining Heat of Combustion Experimentally: q = mcΔT where q is energy, c is specific heat capacity (often 4.18 for water), and ΔT is temperature change.
    • Specific Heat Capacity: Amount of energy to raise the temperature of 1g of a substance by 1K. Water has a high specific heat capacity (4.18), requiring lots of energy for temperature increases.

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    Description

    This quiz covers the various types of chemical reactions including synthesis, decomposition, acid-base, combustion, and precipitation reactions. Understand the examples and characteristics of each reaction type to enhance your chemistry knowledge. Test your comprehension with this engaging quiz!

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