IBSL Chemistry Topic 6 Kinematics Multiple Choice Questions
- 1.
Reactions between aqueous solutions of sodium thiosulfate and acid can be followed by timing the appearance of the solid sulfur that is produced. The time required for the appearance of sulfur would be increased by which of the following changes?
- A.
Raising the temperature
- B.
Diluting the solution
- C.
Adding a catalyst
- D.
Increasing the concentration of the sodium thiosulfate
Correct Answer
B. Diluting the solutionExplanation
Diluting the solution would increase the time required for the appearance of sulfur. This is because diluting the solution decreases the concentration of sodium thiosulfate and acid, which in turn slows down the reaction rate. As a result, it takes longer for the reactants to come into contact and form the solid sulfur product.Rate this question:
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- 2.
The reaction between excess calcium carbonate and hydrochloric acid can be followed by measuring the volume of carbon dioxide produced with time. The results of one such reaction are shown below. How does the rate if this reaction change with time and what is the main reason for this change?
- A.
The rate increases with time because the calcium carbonate particles get smaller
- B.
The rate increases with time because the acid becomes more dilute
- C.
The rate decreases with time because the calcium carbonate particles gets smaller
- D.
The rate decreases with time because the acid becomes more dilute
Correct Answer
D. The rate decreases with time because the acid becomes more diluteExplanation
The correct answer is that the rate decreases with time because the acid becomes more dilute. This is because as the reaction progresses, the hydrochloric acid is consumed and its concentration decreases. Since the rate of a reaction is directly proportional to the concentration of the reactants, a decrease in acid concentration leads to a decrease in the reaction rate. The size of the calcium carbonate particles is not mentioned in the question and therefore cannot be the main reason for the change in reaction rate.Rate this question:
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- 3.
The rate of reaction of a strip of magnesium an 50 cm3 of 1 mol dm-3 HCl is determined at 25 C. In which case would both new conditions contribute to an increase in the rate of reaction?
- A.
Mg powder and 100 cm3 of 1 mol. dm-3 HCl
- B.
Mg powder and 50 cm3 of 0.8 mol. dm-3 HCl
- C.
100 cm3 of 1 mol dm-3 HCl at 30 C
- D.
50 cm3 of 1.2 mol dm-3 HCl at 30 C
Correct Answer
D. 50 cm3 of 1.2 mol dm-3 HCl at 30 CExplanation
In this question, the rate of reaction is determined by the concentration of the HCl solution and the temperature. Increasing the concentration of the HCl solution will increase the rate of reaction because there are more HCl particles available to react with the magnesium. Additionally, increasing the temperature will also increase the rate of reaction because it provides more energy for the particles to collide and react. Therefore, the case where both new conditions contribute to an increase in the rate of reaction is when there is 50 cm3 of 1.2 mol dm-3 HCl at 30 C.Rate this question:
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- 4.
Calcium carbonate and hydrochloric acid react according to the equation below: Which conditions will produce the fastest rate of reaction?
- A.
1 mol dm-3 HCl and CaCO3 pieces
- B.
2 mol dm-3 HCl and CaCO3 pieces
- C.
1 mol dm-3 HCl and CaCO3 powder
- D.
2 mol dm-3 HCl and CaCO3 power
Correct Answer
D. 2 mol dm-3 HCl and CaCO3 powerExplanation
The concentration of the hydrochloric acid affects the rate of reaction. A higher concentration of HCl (2 mol dm-3) will result in a faster rate of reaction compared to a lower concentration (1 mol dm-3). Additionally, using CaCO3 powder instead of pieces will also increase the rate of reaction. This is because a larger surface area is exposed to the acid when using powder, allowing for more collisions between the reactant particles and increasing the rate of reaction.Rate this question:
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- 5.
When ammonia is manufactured commercially a catalyst is used. What is the effect of this catalyst? I. to increase the rate of only the forward reaction II. to increase the rates of forward and reverse reactions III. to shift the position of equilibrium and increase the yield of ammonia
- A.
I only
- B.
II only
- C.
III only
- D.
I and III only
Correct Answer
B. II onlyExplanation
The catalyst used in the commercial manufacture of ammonia increases the rates of both the forward and reverse reactions. This means that it speeds up the conversion of reactants into products (forward reaction) and also the conversion of products back into reactants (reverse reaction). The catalyst does not have an effect on the position of equilibrium or the yield of ammonia.Rate this question:
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- 6.
Some collision between reactant molecules do not form products. This is most likely because
- A.
The molecules do not collide in the proper ratio
- B.
The molecules do not have enough energy
- C.
The concentration is too low
- D.
The reaction is at equilibrium
Correct Answer
B. The molecules do not have enough energyExplanation
The correct answer is that the molecules do not have enough energy. This is because for a reaction to occur, the reactant molecules must collide with sufficient energy to overcome the activation energy barrier. If the molecules do not have enough energy, the collision will not result in the formation of products. The other options, such as the molecules not colliding in the proper ratio, low concentration, or being at equilibrium, do not directly relate to the energy required for a successful reaction.Rate this question:
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- 7.
Which of the following is (are) important in determining whether a reaction occurs? I. energy of molecules II. orientation of the molecules
- A.
I only
- B.
II only
- C.
Both I and II
- D.
Neither I nor II
Correct Answer
C. Both I and IIExplanation
Both the energy of molecules and the orientation of the molecules are important in determining whether a reaction occurs. The energy of molecules is crucial because a certain amount of energy is required to break the existing bonds and form new ones. If the energy of the molecules is not sufficient, the reaction may not occur. Additionally, the orientation of the molecules is important because the reactant molecules need to collide in the correct orientation in order for the reaction to take place. If the molecules collide in an incorrect orientation, the reaction may not occur. Therefore, both factors are important in determining whether a reaction occurs.Rate this question:
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- 8.
The reaction between calcium carbonate and hydrochloric acid carried out in an open flask can be represented by the following equation: Which of the measurement below could be used to measure the rate of the reaction? I. the mass of the flask and contents II. the pH of the reaction mixture III. the volume of carbon dioxide produced
- A.
I and II only
- B.
I and III only
- C.
II and III only
- D.
I, II,III
Correct Answer
D. I, II,IIIExplanation
The mass of the flask and contents can be used to measure the rate of the reaction because as the reaction progresses, carbon dioxide gas is produced and escapes from the open flask, resulting in a decrease in the mass of the flask and contents. The pH of the reaction mixture can also be used to measure the rate of the reaction because as the reaction proceeds, hydrochloric acid is consumed and the pH of the mixture will change. Finally, the volume of carbon dioxide produced can be used to measure the rate of the reaction because as the reaction proceeds, more carbon dioxide gas will be produced.Rate this question:
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- 9.
For a given reaction, why does the rate of the reaction increase when the concentration of the reactions are increases?
- A.
The frequency of the molecular collisions increases
- B.
The activation energy increases
- C.
The average kinetic energy of the molecule increases
- D.
The rate constant increases
Correct Answer
A. The frequency of the molecular collisions increasesExplanation
When the concentration of the reactants increases, there are more molecules available to collide with each other. This leads to an increase in the frequency of molecular collisions, which in turn increases the rate of the reaction. As more collisions occur, there is a higher probability of successful collisions that lead to the formation of products. Therefore, the increase in the frequency of molecular collisions is the most likely reason for the increase in the rate of the reaction.Rate this question:
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- 10.
Based on the definition of rate of reaction, which units are used for a rate?
- A.
Mol dm-3
- B.
Mol time-1
- C.
Dm3 time -1
- D.
Mol dm-3 time-1
Correct Answer
D. Mol dm-3 time-1Explanation
The rate of a reaction is defined as the change in concentration of a reactant or product per unit time. Therefore, the units used for a rate are typically expressed in terms of concentration (mol dm-3) divided by time (s, min, etc.), which gives the rate of reaction as mol dm-3 time-1.Rate this question:
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- 11.
The rate of reaction between two gases increases when the temperature is increased and a catalyst is added. Whoch statements are both correct for the effect of these changes on the reaction?
- A.
Increasing temperature increases the collision frequency and adding a catalyst increases the activation energy
- B.
Increasing temperature increases the activation energy and adding a catalyst does not change the activation energy
- C.
Increasing temperature does not change the activation energy and adding a catalyst decreases the activation energy
- D.
Increasing temperature increases the activation energy and adding a catalyst increases the collision frequency
Correct Answer
C. Increasing temperature does not change the activation energy and adding a catalyst decreases the activation energyExplanation
When the temperature is increased, the rate of reaction between two gases increases because it leads to an increase in collision frequency. This is because the higher temperature causes the gas molecules to move faster, resulting in more frequent collisions. On the other hand, adding a catalyst decreases the activation energy required for the reaction to occur. A catalyst provides an alternative pathway for the reaction with a lower activation energy, allowing the reaction to occur more easily. Therefore, the correct statement is that increasing temperature does not change the activation energy and adding a catalyst decreases the activation energy.Rate this question:
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- 12.
Consider the reaction between solid CaCO3 and aqueous HCl. The reaction will be speeded up by an increase in which of the following conditions? I. concentration of the HCl II. size of the CaCO3 particles III. temperature
- A.
I only
- B.
I and III only
- C.
II and III only
- D.
I, II and III
Correct Answer
B. I and III onlyExplanation
Increasing the concentration of HCl will speed up the reaction because it provides more HCl particles for collision with CaCO3, increasing the frequency of successful collisions. Increasing the temperature will also speed up the reaction because it increases the kinetic energy of the particles, leading to more frequent and energetic collisions. However, the size of the CaCO3 particles does not affect the speed of the reaction as it does not change the concentration or kinetic energy of the reactants.Rate this question:
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- 13.
Which of the following is (are) important in determining whether a reaction occurs? I. energy of the molecules II. orientation of the molecules
- A.
I only
- B.
II only
- C.
Both I and II
- D.
Neither I nor II
Correct Answer
C. Both I and IIExplanation
Both the energy of the molecules and the orientation of the molecules are important in determining whether a reaction occurs. The energy of the molecules determines if they have enough energy to overcome the activation energy barrier and initiate the reaction. The orientation of the molecules is important because for a reaction to occur, the molecules must collide in a specific orientation that allows the necessary bonds to be broken and formed. Therefore, both factors are necessary for a reaction to take place.Rate this question:
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- 14.
As the temperature of a reaction between two gases is increased, the rate of the reaction increases. This is mainly because
- A.
The concentrations of the reactants increase.
- B.
The molecules collide more frequently.
- C.
The pressure exerted by the molecules increases.
- D.
The fraction of molecules with the energy needed to react increases
Correct Answer
D. The fraction of molecules with the energy needed to react increasesExplanation
As the temperature of a reaction between two gases is increased, the kinetic energy of the molecules also increases. This leads to a higher fraction of molecules having the energy required to overcome the activation energy barrier and react. Therefore, the rate of the reaction increases. The other options (increased concentrations, increased collisions, and increased pressure) may also have an effect on the reaction rate, but the most significant factor in this case is the increase in the fraction of molecules with sufficient energy.Rate this question:
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- 15.
Some collisions between reactant molecules do not form products. This is most likely because
- A.
The molecules do not collide in the proper ratio.
- B.
The concentration is too low.
- C.
The molecules do not have enough energy.
- D.
The reaction is at equilibrium.
Correct Answer
C. The molecules do not have enough energy.Explanation
The correct answer is that the molecules do not have enough energy. In order for a reaction to occur, the molecules must collide with enough energy to overcome the activation energy barrier. If the molecules do not have enough energy, they will not be able to break the existing bonds and form new ones to create products. The other options, such as the molecules not colliding in the proper ratio or the concentration being too low, may also affect the reaction rate, but the lack of energy is the most likely reason for the lack of product formation.Rate this question:
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- 16.
Which factor(s) will influence the rate of the reaction shown below? NO2 (g) + CO(g) -> NO(g)+ CO2 (g) I. The number of collisions per second II. The energy of the collisions III. The geometry with which the molecules collide
- A.
I only
- B.
II only
- C.
I and II only
- D.
I, II and III
Correct Answer
D. I, II and IIIExplanation
The rate of the reaction shown will be influenced by the number of collisions per second, the energy of the collisions, and the geometry with which the molecules collide. The number of collisions per second is important because a higher collision frequency increases the chances of successful collisions. The energy of the collisions is crucial because it determines whether the collisions have enough energy to overcome the activation energy barrier and proceed with the reaction. The geometry with which the molecules collide is significant because it affects the orientation of the reactant molecules during collision, which can impact the reaction rate.Rate this question:
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- 17.
The reaction between nitrogen and oxygen in the atmosphere under normal conditions is extremely slow. Which statement best explains this?
- A.
The concentration of oxygen is much lower than that of nitrogen
- B.
The molar mass of nitrogen is less than that of oxygen
- C.
The frequency of collisions between nitrogen and oxygen molecules is lower than that between nitrogen molecules themselves
- D.
Very few nitrogen and oxygen molecules have sufficient energy to react
Correct Answer
D. Very few nitrogen and oxygen molecules have sufficient energy to reactExplanation
The statement "Very few nitrogen and oxygen molecules have sufficient energy to react" best explains why the reaction between nitrogen and oxygen in the atmosphere under normal conditions is extremely slow. This suggests that the majority of nitrogen and oxygen molecules do not possess the necessary energy to overcome the activation energy barrier and initiate a reaction.Rate this question:
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- 18.
Sn(s) +2Fe3+ (aq) → Sn +2 (aq) 2Fe2+ (aq) Tin metal reacts with aqueous Fe3+ ions according to the equation above. Which of the following factors will increase the rate of this reaction? I. Increasing the Fe3+ ion concentration II. Decreasing the size of the tin pieces
- A.
I only
- B.
II only
- C.
Both I and II
- D.
Neither I nor II
Correct Answer
C. Both I and IIExplanation
Increasing the Fe3+ ion concentration will increase the rate of the reaction because there will be more Fe3+ ions available to react with the tin metal. This will increase the frequency of successful collisions between the reactant particles and therefore increase the rate of the reaction. Decreasing the size of the tin pieces will also increase the rate of the reaction because it will increase the surface area of the tin metal available for reaction. This will increase the number of active sites for the reaction to occur, leading to an increase in the rate of the reaction.Rate this question:
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- 19.
The following graph was plotted from the results of an experiment to find the rate of reaction between solid calcium carbonate and aqueous hydrochloric acid. It can be deduced from the graph that
- A.
The rate of the reaction increases with time.
- B.
The concentration of the acid decreases with time.
- C.
The reaction is reversible.
- D.
The reaction is exothermic.
Correct Answer
B. The concentration of the acid decreases with time.Explanation
The graph shows a decrease in the concentration of the acid over time, indicating that it is being consumed in the reaction. This suggests that the acid is reacting with the calcium carbonate to form a product, causing the concentration of the acid to decrease. The other options cannot be deduced from the information given in the question.Rate this question:
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- 20.
In general, the rate of a reaction can be increased by all of the following except
- A.
Increasing the temperature.
- B.
Increasing the concentration of reactants
- C.
Increasing the activation energy.
- D.
Increasing the surface area of the reactants.
Correct Answer
C. Increasing the activation energy.Explanation
Increasing the activation energy does not increase the rate of a reaction. Activation energy is the minimum energy required for a reaction to occur. By increasing the activation energy, it becomes more difficult for the reactants to reach the required energy level, thus slowing down the reaction rate. Therefore, increasing the activation energy does not contribute to increasing the rate of a reaction.Rate this question:
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- 21.
Under what conditions is the rate of reaction of magnesium with HCl(aq) fastest?
- A.
10ml of 1.0 mol dm-3 HCl(aq) at 25oC
- B.
10ml of 2.0 mol dm-3 HCl(aq) at 35 oC
- C.
10ml of 2.0 mol dm-3 HCl(aq) at 25oC
- D.
10ml of 1.0 mol dm-3 HCl(aq) at 35oC
Correct Answer
B. 10ml of 2.0 mol dm-3 HCl(aq) at 35 oCExplanation
The rate of reaction between magnesium and HCl increases with an increase in concentration of HCl and temperature. In this case, the highest concentration of HCl is 2.0 mol dm-3 and the highest temperature is 35oC, so the rate of reaction will be fastest under these conditions.Rate this question:
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- 22.
CaCO3 (s) + 2HCl(aq) → CaCl2 (aq) + H2O(l) + CO2 (g) Which change will increase the rate of the reaction when 50 cm3 of 1.0 mol dm−3 HCl is added to 1.0 g of CaCO3 ?
- A.
The volume of HCl is increased.
- B.
The concentration of HCl is decreased.
- C.
The size of the CaCO3 solid particles is decreased.
- D.
The pressure of the CO2 is increased. The pressure of the CO2 is increased.
Correct Answer
C. The size of the CaCO3 solid particles is decreased.Explanation
By decreasing the size of the CaCO3 solid particles, the surface area of the particles is increased. This allows for more contact between the CaCO3 and the HCl, increasing the frequency of successful collisions and therefore increasing the rate of the reaction. Increasing the pressure of the CO2 would not affect the rate of the reaction as it is a gas and does not directly interact with the solid CaCO3 or the HCl.Rate this question:
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- 23.
Which statement(s) about the following reaction at 100OC is/are correct? N2 (g) + 3H2(g) ↔ 2NH3 (g) I. Every collision between N2 and H2 molecules is expected to produce NH3. II. This reaction must involve a collision between one N2 and three H2 molecules.
- A.
I only
- B.
II only
- C.
Both I and II
- D.
Neither I nor II
Correct Answer
D. Neither I nor IIExplanation
Neither statement I nor statement II is correct. In a chemical reaction, not every collision between N2 and H2 molecules will produce NH3. The reaction requires the collision between one N2 molecule and three H2 molecules, which is stated incorrectly in statement II. Therefore, the correct answer is Neither I nor II.Rate this question:
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- 24.
The rate of reaction of a strip of magnesium and 50 cm3 of 1 mol dm-3 HCl is measured at 25°C. In which case would both new conditions contribute to an increase in the rate of reaction?
- A.
Mg powder and 100 cm3of 1 mol dm-3 HCl
- B.
Mg powder and 50 cm3 of 0.8 mol dm-3 HCl
- C.
100 cm3 of 1 mol dm-3 HCl at 30° C
- D.
50 cm3 of 1.2 mol dm-3 HCl at 30° C
Correct Answer
D. 50 cm3 of 1.2 mol dm-3 HCl at 30° CExplanation
In this question, the rate of reaction is being measured for the reaction between magnesium and hydrochloric acid. Generally, an increase in the concentration of the reactants or an increase in temperature leads to an increase in the rate of reaction.
Among the given options, the condition that would contribute to an increase in the rate of reaction is "50 cm3 of 1.2 mol dm-3 HCl at 30° C". This is because the concentration of HCl is higher (1.2 mol dm-3) compared to the other options, and the temperature is also higher (30° C) compared to the initial condition (25° C). Both of these factors would increase the rate of reaction.Rate this question:
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- 25.
The addition of a catalyst to a chemical reaction alters the rate primarily by
- A.
Changing the enthalpy of the reaction.
- B.
Increasing the number of collisions between the reactant molecules in a given time.
- C.
Increasing the fraction of reactant molecules with a given kinetic energy.
- D.
Providing a different reaction pathway.
Correct Answer
D. Providing a different reaction pathway.Explanation
The addition of a catalyst to a chemical reaction alters the rate primarily by providing a different reaction pathway. A catalyst works by lowering the activation energy required for the reaction to occur, allowing the reaction to proceed more quickly. It does this by providing an alternative pathway with a lower activation energy, which allows more reactant molecules to overcome the energy barrier and react. This increases the rate of the reaction by increasing the number of successful collisions between reactant molecules.Rate this question:
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