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CHEMISTRY, M3 EQ-Bank 15

Using collision theory, explain how increasing the temperature of a reaction mixture affects the rate of the reaction.   (3 marks)

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→ According to collision theory, increasing the temperature of a reaction mixture raises the kinetic energy of the reactant molecules.

→ As the molecules move faster, the frequency of collisions increases. In addition, a higher proportion of the molecules have enough energy to overcome the activation energy barrier.

→ As a result, there are more successful collisions per unit of time, leading to a faster reaction rate.

Show Worked Solution

→ According to collision theory, increasing the temperature of a reaction mixture raises the kinetic energy of the reactant molecules.

→ As the molecules move faster, the frequency of collisions increases. In addition, a higher proportion of the molecules have enough energy to overcome the activation energy barrier.

→ As a result, there are more successful collisions per unit of time, leading to a faster reaction rate.

CHEMISTRY, M3 EQ-Bank 14

A student conducted an experiment to investigate how the concentration of hydrochloric acid affects the rate of its reaction with magnesium ribbon. They measured the volume of hydrogen gas produced at regular intervals in reactions using 1.0 M, 2.0 M, and 3.0 M hydrochloric acid, keeping other variables constant.

  1. Explain how the concentration of hydrochloric acid influences the rate of reaction with magnesium, using collision theory.   (2 marks)
  1. Describe how the student could modify the experiment to investigate the effect of temperature on the reaction rate.   (2 marks)
  1. Identify and explain one advantage of a student using digital technologies such as a gas pressure sensor to collect or analyse data from the experiment.   (2 marks)
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a.   \(\ce{[HCl]} influence on the rate of reaction:

→ As the concentration increases, the number of acid particles in a given volume also increases.

→ This leads to more frequent collisions between hydrochloric acid molecules and the magnesium surface.

→ As a result, a higher concentration of hydrochloric acid increases the chance of successful collisions, which increases the reaction rate and causes hydrogen gas to be produced more quickly.
 

b.   Experiment modifications:

→ To investigate the effect of temperature on the reaction rate, the student could modify the experiment by conducting the reaction at different temperatures while keeping the concentration of hydrochloric acid constant.

→ They could use a water bath or hot plate to control the temperature for each trial. For example, the student could perform the reaction at 20°C, 30°C, and 40°C, then measure and compare the volume of hydrogen gas produced over time at each temperature.
 

c.   Advantage of digital technologies:

→ Using a gas pressure sensor in the experiment allows for continuous and precise data collection without human intervention.

→ This reduces the chances of human error when measuring the volume of gas produced manually at intervals, leading to more accurate and reliable results.

→ Additionally, the sensor can automatically record data over time, providing detailed information about the reaction rate that can be easily analysed using digital tools such as graphing software.

Show Worked Solution

a.   \(\ce{[HCl]} influence on the rate of reaction:

→ As the concentration increases, the number of acid particles in a given volume also increases.

→ This leads to more frequent collisions between hydrochloric acid molecules and the magnesium surface.

→ As a result, a higher concentration of hydrochloric acid increases the chance of successful collisions, which increases the reaction rate and causes hydrogen gas to be produced more quickly.
 

b.   Experiment modifications:

→ To investigate the effect of temperature on the reaction rate, the student could modify the experiment by conducting the reaction at different temperatures while keeping the concentration of hydrochloric acid constant.

→ They could use a water bath or hot plate to control the temperature for each trial. For example, the student could perform the reaction at 20°C, 30°C, and 40°C, then measure and compare the volume of hydrogen gas produced over time at each temperature.
 

c.   Advantage of digital technologies:

→ Using a gas pressure sensor in the experiment allows for continuous and precise data collection without human intervention.

→ This reduces the chances of human error when measuring the volume of gas produced manually at intervals, leading to more accurate and reliable results.

→ Additionally, the sensor can automatically record data over time, providing detailed information about the reaction rate that can be easily analysed using digital tools such as graphing software.

CHEMISTRY, M3 EQ-Bank 5 MC

Which of the following best explains how an increase in temperature affects the rate of a chemical reaction?

  1. It increases the energy of the products, making the reaction proceed faster.
  2. It increases the frequency and energy of collisions between reactant molecules.
  3. It decreases the activation energy needed for the reaction.
  4. It decreases the concentration of the reactants, slowing the reaction.
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\(B\)

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→ Increasing the temperature raises the kinetic energy of the reactant molecules, which increases both the frequency of collisions and the energy of these collisions.

→ More frequent and higher-energy collisions result in a higher likelihood of successful collisions that overcome the activation energy, thereby speeding up the reaction.

→ Therefore, the rate of reaction increases with temperature.

\(\Rightarrow B\)

CHEMISTRY, M3 EQ-Bank 1 MC

According to Collision Theory, to increase the rate of a reaction, which of the following must occur? 

  1. A decrease in temperature
  2. An increase in the concentration of a reactant
  3. An increase in the surface area of a reactant
  4. An increase in the frequency of successful collisions
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\(D\)

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→ Options A and C will increase the rate of a reaction but neither “must” occur for the rate of a reaction to increase.

→ The frequency of successful collisions defines the rate of reaction.

\(\Rightarrow D\)

CHEMISTRY, M3 EQ-Bank 8

Collision Theory is a principle of chemistry that can be used to predict the rates of chemical reactions.

Explain how this theory works with reference to an increase in reactant concentration and a decrease in temperature.   (4 marks)

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→ Collision Theory states that for a chemical reaction to occur, reactant particles must collide. A reaction will then only proceed if:

    • Particles collide with sufficient energy \((\text{E}_\text{a}) \)
    • Particles collide with the proper orientation

→ All reactions have a certain amount of particles colliding and exceeding \(\ce{E_{a}}\) which defines the reaction rate. Increasing the rate is achieved through increasing the amount of successful collisions.

Increase in reactant concentration:

→ Increases the number of reactant particles.

→ This increases the number of collisions, which leads to more successful collisions and a higher reaction rate.

Decrease in temperature

→ Decreases the kinetic energy of colliding particles.

→ As the kinetic energy of particles is decreased, they are less likely to exceed the \(\ce{E_{a}}\) required for a successful collision and a lower reaction rate results.

Show Worked Solution

→ Collision Theory states that for a chemical reaction to occur, reactant particles must collide. A reaction will then only proceed if:

    • Particles collide with sufficient energy \((\text{E}_\text{a}) \)
    • Particles collide with the proper orientation

→ All reactions have a certain amount of particles colliding and exceeding \(\ce{E_{a}}\) which defines the reaction rate. Increasing the rate is achieved through increasing the amount of successful collisions.
 

Increase in reactant concentration:

→ Increases the number of reactant particles.

→ This increases the number of collisions, which leads to more successful collisions and a higher reaction rate.
 

Decrease in temperature

→ Decreases the kinetic energy of colliding particles.

→ As the kinetic energy of particles is decreased, they are less likely to exceed the \(\ce{E_{a}}\) required for a successful collision and a lower reaction rate results.

CHEMISTRY M3 EQ-Bank 6

The following graph represents the number of collisions between reactant molecules as a function of their kinetic energy at two different temperatures.

Using collision theory, explain why \(\ce{T_{2}}\) results in a greater number of successful reactant molecule collisions.   (3 marks)
 

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→ Successful reactant collisions occur when the kinetic energy of the reactant particles the activation energy required \( (\text{E}_\text{a})\).

→ From the above graph, we can see that at the kinetic energy level \( (\text{E}_\text{a})\), the \(\ce{T_{2}}\) graph has more reactant particles colliding. It follows that \(\ce{T_{2} > T_{1}}\).

→ Collision theory states that an increase in temperature increases the kinetic energy of reactant particles and thus the force of their collision. Increasing the force of collision means that the amount of successful collisions converting reactants into products is greater, increasing the reaction rate. 

Show Worked Solution

→ Successful reactant collisions occur when the kinetic energy of the reactant particles the activation energy required \( (\text{E}_\text{a})\).

→ From the above graph, we can see that at the kinetic energy level \( (\text{E}_\text{a})\), the \(\ce{T_{2}}\) graph has more reactant particles colliding. It follows that \(\ce{T_{2} > T_{1}}\).

→ Collision theory states that an increase in temperature increases the kinetic energy of reactant particles and thus the force of their collision. Increasing the force of collision means that the amount of successful collisions converting reactants into products is greater, increasing the reaction rate. 

CHEMISTRY, M3 EQ-Bank 2

Explain how decreasing temperature in an exothermic reaction influences the rate of a chemical reaction.   (2 marks)

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→ In an exothermic reaction, heat is released as the reaction progresses from the reactants to the products.

→ Decreasing the temperature in an exothermic reaction leads to a decrease in the reaction rate.

→ A decrease in temperature lowers the kinetic energy of particles which leads to less successful collisions that exceed activation energy \(\ce{(E_{a})}\) and therefore decreases the reaction rate.

Show Worked Solution

→ In an exothermic reaction, heat is released as the reaction progresses from the reactants to the products.

→ Decreasing the temperature in an exothermic reaction leads to a decrease in the reaction rate.

→ A decrease in temperature lowers the kinetic energy of particles which leads to less successful collisions that exceed activation energy \(\ce{(E_{a})}\) and therefore decreases the reaction rate.

CHEMISTRY, M3 EQ-Bank 1

Explain how increasing temperature in an endothermic reaction influences the rate of a chemical reaction.  (2 marks)

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Show Worked Solution

→ In an endothermic reaction heat is absorbed as the reaction progresses from reactants to products.

→ An increase in temperature raises the kinetic energy of particles and leads to more successful particle collisions that exceed activation energy \(\ce{(E_{a})}\) thus increasing the reaction rate.

CHEMISTRY, M3 2013 VCE 14-15 MC

\(\ce{Cu(s) + 4HNO3(aq)\rightarrow Cu(NO3)2(aq) + 2NO2(g) + 2H2O(l)}\)
 

\(\text{Question 14}\)

Which one of the following will not increase the rate of the above reaction?

  1. decreasing the size of the solid copper particles
  2. increasing the temperature of \(\ce{HNO3}\) by 20 °C
  3. increasing the concentration of \(\ce{HNO3}\)
  4. allowing \(\ce{NO2}\) gas to escape

 
\(\text{Question 15}\)

In the above reaction, the number of successful collisions per second is a small fraction of the total number of collisions.

The major reason for this is that

  1. the nitric acid is ionised in solution.
  2. some reactant particles have too much kinetic energy.
  3. the kinetic energy of the particles is reduced when they collide with the container’s walls.
  4. not all reactant particles have the minimum kinetic energy required to initiate the reaction.
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\(\text{Question 14:}\ D\)

\(\text{Question 15:}\ D\)

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\(\text{Question 14}\)

→ Options \(A, B\) and \(C\) will all increase the rate of the given chemical reaction.

\(\Rightarrow D\)
 

\(\text{Question 15}\)

→ Successful collisions occur only if the particles involved have at least the minimum kinetic energy required and the correct orientation.

\(\Rightarrow D\)