Chemistry Chapter on Reaction Rates and Enzymes
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Questions and Answers

Which factor does NOT affect the speed of a reaction?

  • Particle size
  • Color of reactants (correct)
  • Temperature
  • Concentration

    • Increasing the temperature of a reaction generally speeds up the rate of reaction.

    True

    What are the two main methods to measure the speed of a reaction?

    Timing the reaction completion and measuring the amount of product or reactant.

    The ______ of a reactant can significantly influence the speed of a reaction.

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

    Match the following speed of reaction factors with their description:

    <p>Particle Size = Smaller particles increase surface area for reactions. Concentration = Higher amounts of reactants lead to faster reactions. Pressure = Increased pressure can speed up reactions involving gases. Temperature = Higher temperatures typically increase reaction rates.</p> Signup and view all the answers

    Which of the following is an example of an exothermic reaction?

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

    Exothermic reactions result in a positive ΔH value.

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

    What is the primary function of enzymes in industrial applications?

    <p>To catalyze chemical reactions.</p> Signup and view all the answers

    Yeast convert sugars into __________ and carbon dioxide by fermentation.

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

    Match the following enzymes with their industrial uses:

    <p>Protease = Tenderizing tough meat Amylase = Converting starches to sugars Lipase = Breaking down fats Cellulase = Digesting cellulose in plant materials</p> Signup and view all the answers

    What is a common product of an exothermic reaction?

    <p>Heat energy</p> Signup and view all the answers

    Fungal enzymes can be used to produce antibiotics like penicillin.

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

    What type of reaction occurs when products have less energy than the reactants?

    <p>Exothermic reaction</p> Signup and view all the answers

    What is the catalyst used in the manufacture of ethanol from ethene and steam?

    <p>Phosphoric acid</p> Signup and view all the answers

    The reaction to produce ethanol is non-reversible.

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

    What is the chemical equation for the production of ethanol from ethene?

    <p>C2H4(g) + H2O &lt;=&gt; C2H5OH(g)</p> Signup and view all the answers

    Ethanol can be manufactured by reacting ethene and _____ in the presence of phosphoric acid.

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

    Match the temperature with the corresponding percentage of ethanol produced at 60 atmospheres:

    <p>200°C = 49% 260°C = 38% 320°C = 34%</p> Signup and view all the answers

    What effect does increasing pressure have on the equilibrium in a reaction that produces ethanol?

    <p>It shifts the equilibrium to the right.</p> Signup and view all the answers

    At what temperature does the production of ethanol yield the highest percentage?

    <p>200°C</p> Signup and view all the answers

    Is the formation of ethanol exothermic or endothermic?

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

    The formation of ethanol is an endothermic process.

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

    One use of ethanol is the manufacture of _____ acid.

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

    What type of acid is mentioned as a product in the reaction described?

    <p>ethanoic acid</p> Signup and view all the answers

    The bond energy of H - H is _____ kJ/mol.

    <p>436</p> Signup and view all the answers

    Match the following bonds with their corresponding bond energy in kJ/mol:

    <p>H - Cl = 431 C - H = 412 N = N = 409 Cl - Cl = 242</p> Signup and view all the answers

    What is the bond energy of the C - C bond?

    <p>348 kJ/mol</p> Signup and view all the answers

    As temperature increases, the amount of ethanol produced increases.

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

    What is the primary reaction in engines that creates heat energy?

    <p>2H<del>2</del> (g) + O<del>2 (g) ightarrow 2H</del>2~O (g) + heat</p> Signup and view all the answers

    Fuel cells convert chemical energy directly into heat energy.

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

    What type of ion reacts with hydrogen in a fuel cell to produce water and electrons?

    <p>hydroxide ion</p> Signup and view all the answers

    In a fuel cell, hydrogen and hydroxide ions react on a _________ to generate negatively charged electrodes.

    <p>platinum catalyst</p> Signup and view all the answers

    Match the components or terms related to fuel cells with their correct descriptions:

    <p>Anode = The negatively charged electrode Electrolyte = Conducts ions within the fuel cell Fuel Cell = Device converting chemical energy to electrical energy Cathode = The positively charged electrode</p> Signup and view all the answers

    What is the result of hydrogen reacting with hydroxide ions in the fuel cell?

    <p>Electrons are released</p> Signup and view all the answers

    Heat energy is primarily used for daily appliances.

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

    The main purpose of the heat generated in engines is to ________ the vehicle forward.

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

    What happens when bonds are formed in a reaction?

    <p>Heat is released and ΔH is negative.</p> Signup and view all the answers

    Breaking bonds in a reaction is an exothermic process.

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

    What is the bond energy of H–H?

    <p>436 kJ/mol</p> Signup and view all the answers

    In an endothermic reaction, ΔH is ______.

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

    Which bond requires the least amount of energy to break?

    <p>Br–Br</p> Signup and view all the answers

    Match the following terms with their correct descriptions:

    <p>Exothermic = Heat is released and ΔH is negative Endothermic = Heat is absorbed and ΔH is positive Bond breaking = Absorption of heat energy Bond formation = Release of heat energy</p> Signup and view all the answers

    The reaction that forms HBr from H2 and Br2 is exothermic.

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

    Study Notes

    Rate of Reaction

    • Rate of reaction is inversely proportional to time taken; the shorter the time needed for reaction to complete, the faster the speed of the reaction.
    • Speed of reaction = 1/time taken
    • Measuring the amount of product produced in a period of time or measuring the amount of reactant remaining in a period of time is another method.
    • This can be measured by plotting changes in volume of gas evolved, mass of reaction mixture, or changes in pressure of gas formed.
    • Measuring evolved gas: A common example includes the reaction of limestone with acid which produces carbon dioxide. A syringe is used for measurement of gas produced at time intervals. The volume of gas is graphed against time.
    • Measuring changes in mass: Marble reacted with acid in a flask with cotton wool to prevent splashing. The readings on a balance are plotted on a graph at time intervals

    Factors Affecting Speed of Reaction

    • Particle size of reactant: Smaller particles result in a faster reaction rate. This is because a larger surface area allows for more collisions between reactant particles.
    • Concentration of reactant: Higher concentration increases reaction rate. Increased reactant particles in a given volume results in more frequent collisions.
    • Pressure of reactant: Higher pressure increases the reaction rate, especially for gaseous reactions. The molecules are forced to move closely, leading to more collisions.
    • Temperature: Increased temperature increases reaction rate. Increased temperature supplies more energy for the particle collisions. The collisions are more forceful.
    • Effect of catalyst: Catalysts speed up reactions without being consumed in the process. They provide an alternative reaction pathway with a lower activation energy.
    • Enzymes*: biological catalysts
      • Specific to one type of reaction
    • Sensitive to temperature (40°C usually)
    • Sensitive to pH level

    Exothermic and Endothermic Reactions

    • Exothermic reactions: Release heat energy, ΔΗ (heat change) has a negative value. The energy released from forming products is greater than the energy absorbed from breaking bonds in reactants
    • Endothermic reactions: Absorb heat energy, ΔΗ has a positive value. The energy absorbed to break bonds in reactants is greater than the energy released from forming products.
    • Examples of exothermic changes: Changes of state (gas to liquid or solid), combustion (burning) reactions, and dissolving of anhydrous salts/acids in water; Example: dissolving of Na2CO3 in water or CuSO4.
    • Examples of endothermic reactions: Melting, evaporation, photolysis (reaction with light), decomposition using heat, dissolving ionic compounds, and acid reacting with bicarbonates. Example: Reaction of light sensitive silver chloride in a camera.

    Fuels

    • Fuels are substances that release energy when burned (oxidized).
    • Common fuels include methane, wood, oil, natural gas, and hydrogen
    • Combustion in air provides energy and gives out heat

    Hydrogen as a Fuel

    • Hydrogen burns cleanly in air forming steam.
    • Hydrogen provides double the heat energy per gram compared to other fuels). Hydrogen production (methods): Electrolysis of water, or cracking of hydrocarbons.

    Fuel Cells

    • Fuel cells directly convert chemical energy into electrical energy.
    • Hydrogen reacts with hydroxide ions to form water and release electrons
    • Oxygen takes in electrons to create hydroxide ions

    Petroleum

    • A mixture of hydrocarbons, refined (separated into different fractions)
    • Crude oil heated to 350°C, vapors rise.
    • Different fractions condense at different temperatures, collected in a fractionating column

    Photosynthesis

    • Plants take in carbon dioxide and water in presence of sunlight and chlorophyll to synthesize glucose and release oxygen.
    • This is crucial as glucose provides plants energy.

    Additional Topics

    • Measuring time for completion of reaction
    • Activation energy
    • Factors influencing rate of reaction
    • Energy profile diagram for reaction

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    Chemical Reaction PDF

    Description

    Explore the fundamental concepts of chemical reactions, including factors that influence their speed, catalytic processes, and the role of enzymes in industry. This quiz covers exothermic reactions and methods to measure reaction rates. Test your knowledge about reaction dynamics and industrial applications of biochemistry.

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