Chemistry Reaction Rates Quiz

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Questions and Answers

Which of the following factors can affect the speed of a chemical reaction?

  • Particle size
  • Concentration
  • Temperature
  • All of the above (correct)

Enzymes are inorganic catalysts.

False (B)

What is a catalyst?

A substance that increases the speed of a chemical reaction without being consumed in the process.

The total volume of gas produced in a reaction will ___________ as the reaction proceeds.

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

Match the following methods of measuring reaction speed with their corresponding descriptions:

<p>Measure the amount of product formed = Determine how much gas is produced over time Measure the amount of reactant used = Determine how much material is consumed over time Measure changes in mass = Observe the mass of the reaction mixture over time</p> Signup and view all the answers

What does the gradient of a volume of gas evolved against time graph indicate?

<p>The speed of the reaction (B)</p> Signup and view all the answers

The speed of reaction remains constant throughout the entire process.

<p>False (B)</p> Signup and view all the answers

At what time does the gradient of the mass against time graph become zero?

<p>5 min</p> Signup and view all the answers

The speed of reaction decreases as the reactants are _________.

<p>used up</p> Signup and view all the answers

Match the following statements regarding the reaction's progress:

<p>The gradient is steepest = The speed of the reaction is fastest The gradient decreases = Reactants being consumed The gradient becomes 0 = No more gas is being produced The reaction has stopped = Speed of reaction = 0</p> Signup and view all the answers

What happens to the amount of gas produced over time during the reaction?

<p>It increases, then levels off (D)</p> Signup and view all the answers

The apparatus can measure both volume of gas evolved and mass of the reaction mixture.

<p>True (A)</p> Signup and view all the answers

What does a horizontal line on the volume of gas evolved against time graph represent?

<p>The reaction has stopped producing gas.</p> Signup and view all the answers

Which of the following factors does NOT affect the speed of a chemical reaction?

<p>Color of the reactants (A)</p> Signup and view all the answers

The more reactant particles collide, the slower the reaction will be.

<p>False (B)</p> Signup and view all the answers

What is the term used to describe the minimum energy required for a reaction to occur?

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

The total volume of gas evolved during the reaction was _____ cm3.

<p>70</p> Signup and view all the answers

Match the following factors with their effects on the speed of a reaction:

<p>Increase in concentration = Increases effective collisions Increase in temperature = Increases particle energy Presence of a catalyst = Lowers activation energy Increase in pressure = Increases gas particle frequency</p> Signup and view all the answers

What is the expected outcome of increasing the temperature of reactants?

<p>Increased frequency of collisions (B)</p> Signup and view all the answers

Why is a catalyst used in chemical reactions?

<p>To lower the activation energy.</p> Signup and view all the answers

A fast reaction will always produce a larger volume of gas compared to a slow reaction under the same conditions.

<p>False (B)</p> Signup and view all the answers

Which factor contributes to an increased speed of reaction due to a larger surface area?

<p>Size of reacting particles (A)</p> Signup and view all the answers

Increasing the pressure of a gas decreases the speed of a chemical reaction.

<p>False (B)</p> Signup and view all the answers

What happens to the speed of reaction when the temperature increases?

<p>The speed of reaction increases.</p> Signup and view all the answers

The Haber process operates at high pressure of _____ atm.

<p>250</p> Signup and view all the answers

What is the main reason for the increase in reaction speed when particle size decreases?

<p>More collisions occur (D)</p> Signup and view all the answers

Smaller reactant particles lead to a decrease in the frequency of effective collisions.

<p>False (B)</p> Signup and view all the answers

Name one factor that increases the speed of a chemical reaction.

<p>Temperature, pressure, or concentration.</p> Signup and view all the answers

What is the primary function of a catalyst in a chemical reaction?

<p>To increase the reaction speed without being consumed (D)</p> Signup and view all the answers

Enzymes can function effectively only within a wide range of pH levels.

<p>False (B)</p> Signup and view all the answers

What term is used for substances that prevent catalysts from functioning effectively?

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

A catalyst provides an alternative pathway with a lower _________ energy for the reaction to proceed.

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

Match the following characteristics with the correct statements:

<p>Catalysts = Remain unchanged after the reaction Enzymes = Proteins that act as biological catalysts Catalysts are selective = Different reactions require different catalysts Enzymes are sensitive = Affected by temperature and pH changes</p> Signup and view all the answers

What effect does an enzyme have on a reaction?

<p>Decreases the activation energy (A)</p> Signup and view all the answers

All catalysts are transition metals or their compounds.

<p>False (B)</p> Signup and view all the answers

Enzymes generally double the rate of reaction for every _______ degree Celsius increase in temperature until denaturation occurs.

<p>10</p> Signup and view all the answers

Flashcards

Reaction Rate

The speed at which a chemical reaction occurs.

Measuring Reaction Rate

The rate of reaction is measured by the amount of reactant used up or the amount of product formed in a given time.

Factors Affecting Reaction Rate

Factors that affect the speed of a reaction, such as temperature, concentration, surface area and catalysts.

Catalyst

A substance that speeds up a reaction without being used up in the process.

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Enzymes

Biological catalysts, typically proteins, that speed up biochemical reactions in living organisms.

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Gradient

The steepness of a line on a graph, calculated by dividing the change in the y-axis by the change in the x-axis.

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Speed of Reaction

How fast a chemical reaction happens. Measured by how quickly the products are formed or reactants disappear.

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Start of Reaction

The speed of reaction is fastest at the beginning because all reactants are present and available for interaction.

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As Reaction Proceeds

As the reaction proceeds, the concentration of reactants decreases, causing the speed of reaction to slow down.

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Reaction Ends

The speed of reaction reaches zero when the reaction is complete and no more reactants remain.

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Volume of Gas vs. Time Graph

A graph showing the relationship between the volume of gas produced and the time taken for a reaction.

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Mass vs. Time Graph

A graph showing the mass of reactants against time, depicting how the mass changes as the reaction progresses.

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Change in Mass

A way to measure the reaction rate by observing the change in mass over time. The steepest gradient indicates the fastest reaction.

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Activation Energy

The minimum amount of energy required for a chemical reaction to occur.

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Collision Theory

A theory that explains how chemical reactions occur. It states that reactant particles must collide with sufficient energy to break bonds and form new ones.

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Effect of Concentration on Reaction Rate

Increasing the concentration of reactants increases the frequency of collisions between reactant particles, leading to a faster rate of reaction.

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Effect of Temperature on Reaction Rate

Increasing the temperature increases the kinetic energy of reactant particles, making them more likely to collide with sufficient energy to react. This increases the reaction rate.

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Volume of Gas Evolved

The volume of gas produced at the end of a reaction is the same, regardless of the time taken. A fast reaction produces the same amount of gas as a slow reaction, but in a shorter time.

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How does particle size affect reaction rate?

Smaller particle size leads to a larger surface area exposed for reactions. This increases the frequency of collisions, resulting in more effective collisions and a faster reaction.

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How does pressure affect reaction rate?

Increasing pressure on gaseous reactants forces particles closer together, increasing their concentration. This leads to more frequent collisions and a faster reaction.

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How does temperature affect reaction rate?

Higher temperature means faster-moving particles with more energy. This increases the likelihood of successful collisions that overcome the activation energy barrier, making the reaction faster.

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What is activation energy?

The minimum energy required for reactants to collide and initiate the reaction.

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Why is pressure only relevant for reactions involving gases?

Reactions involving gases are more likely to be affected by pressure because increasing pressure allows particles to collide more frequently due to increased concentration.

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How does the Haber process illustrate pressure's effect on reaction rate?

The Haber process is a reaction that produces ammonia from nitrogen and hydrogen gas. It requires high pressure (250 atm) to speed up the reaction.

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What is the marble and acid reaction?

The reaction between marble (calcium carbonate) and hydrochloric acid, producing carbon dioxide gas.

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How does the size of marble affect the reaction rate with acid?

The larger the surface area of the marble, the more readily it reacts with the acid. Breaking the marble into smaller pieces provides a greater surface area, leading to faster reaction rate.

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How Catalysts Work

Catalysts lower the activation energy of a reaction, providing an alternative pathway for it to proceed.

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Substrate

The molecule that an enzyme acts upon.

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Enzyme Specificity

Enzymes are highly specific, meaning each enzyme works on a specific type of substrate.

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Temperature and Enzyme Activity

Enzymes function best within a narrow range of temperatures.

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pH and Enzyme Activity

Enzymes function best within a narrow pH range.

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Study Notes

Speed of Reaction

  • Reactions proceed at different rates, ranging from very fast (explosions) to very slow (rusting).
  • Methods to measure reaction rate include measuring product formation, reactant consumption, or changes during the reaction over time.

Measuring Reaction Rate

  • Reaction rate can be measured by monitoring the volume of gas produced (e.g., using a gas syringe) or the mass loss (e.g., using a balance) over time.
  • Data collected can be plotted as graphs (volume/mass vs. time)
  • The gradient of the graph represents the reaction rate (steeper gradient = faster reaction).

Factors Affecting Reaction Rates

  • Particle Size: Smaller particles have a larger surface area, leading to more frequent collisions and faster reactions.
  • Concentration: Higher concentration means more particles per unit volume, increasing collision frequency and reaction rate.
  • Temperature: Higher temperatures provide particles with more kinetic energy, leading to more frequent and energetic collisions. Increasing temperature generally doubles reaction rate with every 10°C increase.
  • Pressure: Increasing pressure for gaseous reactants increases the concentration, increasing the frequency of collisions.
  • Catalysts: Catalysts speed up reactions by providing an alternative reaction pathway with lower activation energy. Catalysts are unchanged after the reaction.
  • Enzymes: Enzymes are biological catalysts that work by lowering activation energy, speeding up biochemical reactions. Their activity is affected by temperature and pH.

Collision Theory

  • Reactions only occur when reacting particles collide with sufficient energy (activation energy).
  • The more collisions per unit time and the more energetic the collisions, the faster the reaction.
  • Collision theory explains how factors such as concentration, temperature, and particle size affect reaction rates.

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