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Questions and Answers
The instantaneous rate at 2 minutes is calculated as 30/2.9.
The instantaneous rate at 2 minutes is calculated as 30/2.9.
True
The rate of reaction is inversely proportional to the concentration of Na2S2O3.
The rate of reaction is inversely proportional to the concentration of Na2S2O3.
False
Covalent bonds break and form easily, leading to faster reactions compared to ionic bonds.
Covalent bonds break and form easily, leading to faster reactions compared to ionic bonds.
False
A catalyst is consumed during a chemical reaction.
A catalyst is consumed during a chemical reaction.
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The volume of hydrogen produced increases steadily over time in the experiment.
The volume of hydrogen produced increases steadily over time in the experiment.
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Finely divided particles can lead to dust explosions due to their high surface area.
Finely divided particles can lead to dust explosions due to their high surface area.
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The temperature of the sodium thiosulfate solution must be increased to observe a change in reaction rate.
The temperature of the sodium thiosulfate solution must be increased to observe a change in reaction rate.
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The reaction is fastest at the beginning and then becomes increasingly slower.
The reaction is fastest at the beginning and then becomes increasingly slower.
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The procedure involves adding hydrochloric acid before starting the stopwatch.
The procedure involves adding hydrochloric acid before starting the stopwatch.
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Temperature does not affect the rate of a chemical reaction.
Temperature does not affect the rate of a chemical reaction.
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Catalysts are effective in very large amounts for a reaction.
Catalysts are effective in very large amounts for a reaction.
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The disappearance of the cross on paper is a method for timing the reaction of sodium thiosulfate with hydrochloric acid.
The disappearance of the cross on paper is a method for timing the reaction of sodium thiosulfate with hydrochloric acid.
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Powdered chemicals react more slowly than large pieces of the same substance.
Powdered chemicals react more slowly than large pieces of the same substance.
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The slope of the tangent line at the two-minute mark represents the instantaneous rate of reaction.
The slope of the tangent line at the two-minute mark represents the instantaneous rate of reaction.
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The final temperature recorded should be the temperature of the hydrochloric acid.
The final temperature recorded should be the temperature of the hydrochloric acid.
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A graph of 1/time against temperature can be drawn to analyze reaction rates.
A graph of 1/time against temperature can be drawn to analyze reaction rates.
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A dust explosion can occur if there are combustible particles, a source of ignition, dry particles, and presence of carbon dioxide.
A dust explosion can occur if there are combustible particles, a source of ignition, dry particles, and presence of carbon dioxide.
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Higher concentration of reactants decreases the rate of reaction.
Higher concentration of reactants decreases the rate of reaction.
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Increasing the temperature of a reaction decreases the number of collisions between particles.
Increasing the temperature of a reaction decreases the number of collisions between particles.
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The initial concentration of sodium thiosulfate in the experiment is 0.1 M.
The initial concentration of sodium thiosulfate in the experiment is 0.1 M.
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The rate of reaction can be expressed as the change in time over the change in concentration.
The rate of reaction can be expressed as the change in time over the change in concentration.
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The mandatory experiment involves using sodium thiosulfate solution and acetic acid to study the effect of concentration on reaction rate.
The mandatory experiment involves using sodium thiosulfate solution and acetic acid to study the effect of concentration on reaction rate.
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Increasing the amount of catalyst significantly alters the rate of the reaction.
Increasing the amount of catalyst significantly alters the rate of the reaction.
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In the experiment, the cross placed on white paper disappears as the reaction proceeds, and the time taken is recorded.
In the experiment, the cross placed on white paper disappears as the reaction proceeds, and the time taken is recorded.
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A catalyst can be poisoned by substances such as lead when added to petrol.
A catalyst can be poisoned by substances such as lead when added to petrol.
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The relationship between the rate of reaction and sodium thiosulfate concentration is linear according to the graphical analysis.
The relationship between the rate of reaction and sodium thiosulfate concentration is linear according to the graphical analysis.
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Homogenous catalysis involves reactants and catalysts in different phases.
Homogenous catalysis involves reactants and catalysts in different phases.
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Autocatalysis involves a product of the reaction acting as a catalyst.
Autocatalysis involves a product of the reaction acting as a catalyst.
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Surface Adsorption Theory explains most homogenous catalysis reactions.
Surface Adsorption Theory explains most homogenous catalysis reactions.
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The iodine snake experiment demonstrates heterogenous catalysis.
The iodine snake experiment demonstrates heterogenous catalysis.
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Catalysts help to achieve equilibrium more slowly in a reaction.
Catalysts help to achieve equilibrium more slowly in a reaction.
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An intermediate compound is formed when a catalyst is involved in a chemical reaction.
An intermediate compound is formed when a catalyst is involved in a chemical reaction.
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Catalytic converters contain catalysts such as Nickel, Cobalt, and Gold.
Catalytic converters contain catalysts such as Nickel, Cobalt, and Gold.
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The process in a catalytic converter involves the desorption of products from the surface of the catalyst.
The process in a catalytic converter involves the desorption of products from the surface of the catalyst.
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Carbon monoxide is converted into carbon monoxide in the catalytic converter.
Carbon monoxide is converted into carbon monoxide in the catalytic converter.
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Catalytic converters need to be replaced after approximately 80,000 Km due to catalyst poisoning.
Catalytic converters need to be replaced after approximately 80,000 Km due to catalyst poisoning.
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An effective collision is defined as a collision that does not lead to the formation of products.
An effective collision is defined as a collision that does not lead to the formation of products.
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Lead and sulfur act as catalyst poisons by forming temporary bonds on the catalyst surface.
Lead and sulfur act as catalyst poisons by forming temporary bonds on the catalyst surface.
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The reaction in a catalytic converter is enhanced by a lower concentration of reactants on the surface.
The reaction in a catalytic converter is enhanced by a lower concentration of reactants on the surface.
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A sufficient minimum energy must be exceeded for particles to undergo an effective collision in a reaction.
A sufficient minimum energy must be exceeded for particles to undergo an effective collision in a reaction.
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The Activation Energy is the maximum energy that colliding particles must have for a reaction to occur.
The Activation Energy is the maximum energy that colliding particles must have for a reaction to occur.
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A Reaction Profile Diagram depicts the change in energy of a chemical reaction over time.
A Reaction Profile Diagram depicts the change in energy of a chemical reaction over time.
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A catalyst increases the activation energy required for a reaction.
A catalyst increases the activation energy required for a reaction.
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The rate of reaction can be calculated as the change in concentration per unit time of any two reactants or products.
The rate of reaction can be calculated as the change in concentration per unit time of any two reactants or products.
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As temperature increases, the rate of reaction remains constant.
As temperature increases, the rate of reaction remains constant.
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If the experiment used a lower concentration of sodium thiosulfate, the reaction times would be shorter.
If the experiment used a lower concentration of sodium thiosulfate, the reaction times would be shorter.
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The time taken for the reaction to occur can be approximated by taking the reciprocal of the reaction rate.
The time taken for the reaction to occur can be approximated by taking the reciprocal of the reaction rate.
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The formation of sulfur during the reaction is indicated by the disappearance of a cross under the conical flask.
The formation of sulfur during the reaction is indicated by the disappearance of a cross under the conical flask.
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Study Notes
Rates of Reactions
- Chemists use the term "rate of reaction" to describe how quickly chemical changes occur.
- The rate of reaction is defined as the change in concentration per unit time of any one reactant or product.
Mandatory Experiment: Monitoring the Rate of Oxygen Production
- Materials: Hydrogen peroxide, manganese dioxide, water, conical flask, test tube, thread, stopper, graduated cylinder, beehive shelf, teat pipette, delivery tube, stop clock.
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Procedure:
- Measure and dilute hydrogen peroxide.
- Weigh and suspend manganese dioxide in the flask.
- Fill a graduated cylinder with water and invert over a beehive shelf.
- Inject air into the cylinder to mark the initial water level.
- Allow the thread to fall and shake vigorously, starting the stop clock.
- Record the total volume of oxygen produced every 30 seconds.
- Plot a graph of total volume of oxygen against time.
Instantaneous Rate of Reaction
- The instantaneous rate of reaction is the rate at any one particular time during the reaction.
Factors Affecting Rates of Reactions
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Nature of Reactants:
- The rate depends on the bonds involved (some bonds are easier to break/form than others).
- Ionic bonds are faster than covalent bonds.
- The nature of the reactants makes a difference in the rate that the reaction takes place.
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Particle Size:
- Smaller particles lead to faster reactions due to higher surface area, increasing collisions.
- Powdered chemicals react faster than larger pieces.
- Dust explosions can occur with finely divided particles (combustible particles, ignition source, dry particles, and oxygen are required).
-
Concentration:
- Higher concentrations lead to faster rates as more particles mean greater collision chances.
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Temperature:
- Increased temperatures increase the rate of reaction. This is due to higher kinetic energy and more frequent and energetic collisions, increasing the number of successful collisions.
-
Catalysts:
- Catalysts speed up reactions without being consumed.
Other Experiments (using sodium thiosulfate, hydrochloric acid)
- Purpose: To study the effect of concentration on reaction rate.
- Materials: Sodium thiosulfate solution, hydrochloric acid, conical flask, stop clock, cross on paper.
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Procedure:
- Use different concentrations of sodium thiosulfate.
- Add hydrochloric acid to each.
- Record the time it takes for the cross to disappear.
- Plot a graph of 1/time against concentration.
- Conclusion: The rate of the reaction is directly proportional to the concentration of sodium thiosulfate: a graph of 1/time against concentration shows a direct relationship; if concentration doubles, the reaction rate doubles.
Effect of Temperature on Reaction Rate (using sodium thiosulfate and hydrochloric acid)
- Purpose: To study the effect of temperature on a reaction rate.
- Materials: Sodium thiosulfate solution, hydrochloric acid, conical flask, stop clock, cross on paper, thermometer.
-
Procedure:
- Use different temperatures of sodium thiosulfate.
- Add hydrochloric acid to each, starting the stop clock.
- Record time the cross disappears.
- Conclusion: the graph plots 1/time against temperature shows a relationship where increasing temperature causes rate to increase. Increasing temperature will causes reaction rate to increase exponentially.
Catalysts
- Definition: A substance which alters the rate of reaction but is not consumed in the reaction.
- Homogeneous catalysis: Reactants and catalyst are in the same phase. (e.g., iodine clock experiment, hydrogen peroxide).
- Heterogeneous catalysis: Reactants and catalyst are in different phases. (e.g., oxidation of methanol to methanal).
- Catalyst properties: Catalysts are specific (act on only one type of reaction), only need small amounts to function, and are recovered chemically unchanged.
- Catalytic converters: The platinum, palladium, and rhodium in catalytic converters reduce exhaust pollutants (e.g., carbon monoxide, nitrogen oxides, and hydrocarbons).
Collision Theory and Activation Energy
- Effective collisions: Collisions with sufficient energy to result in product formation.
- Activation energy (Ea): Minimum energy required for an effective collision.
- Reaction profile diagrams: Show the energy change during a reaction, with and without a catalyst. A catalyst lowers the activation energy.
Other Concepts
- Autocatalysis: When one of the products acts as a catalyst for the reaction.
- Catalyst poisons substances that reduce a catalyst's efficiency. (e.g., lead and sulfur).
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Description
This quiz covers the concept of reaction rates in chemistry and focuses on a mandatory experiment involving the monitoring of oxygen production. It explores the defined rate of reaction, materials used, and procedures to accurately measure gas evolution. Test your understanding of how chemical reactions can be quantitatively analyzed.
