Speed Of Reactions
This quiz will check your understanding in what you have learnt.
- 1.
Which of the following statements about the effect of a catalyst is correct?
- A.
It increases the yield of the product.
- B.
It increases the speed of the reactant particles.
- C.
It increases the activation energy of the reaction.
- D.
It provides an alternative pathway for the reaction to occur.
Correct Answer
D. It provides an alternative pathway for the reaction to occur.Explanation
Some catalysts are negative catalysts, which reduces the speed of the reaction.Rate this question:
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- 2.
Dilute sulfuric acid reacts with copper(II) oxide to form copper(II) sulfate and water. What would not alter the rate of this reaction?
- A.
The concentration of the sulfuric acid
- B.
The pressure at which the reaction takes place
- C.
The size of the particles of copper(II) oxide
- D.
The temperature of the reacting mixture
Correct Answer
B. The pressure at which the reaction takes placeExplanation
The pressure at which the reaction takes place does not affect the rate of the reaction. The rate of a chemical reaction is primarily influenced by factors such as concentration, particle size, and temperature. Pressure, on the other hand, mainly affects the reaction rate in gas-phase reactions, where an increase in pressure can increase the number of collisions between gas molecules and therefore increase the reaction rate. In this case, since the reaction involves dilute sulfuric acid and copper(II) oxide, which are not in the gas phase, the pressure does not play a significant role in determining the reaction rate.Rate this question:
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- 3.
Magnesium reacts with hydrochloric acid. Which solution would give the fastest initial rate of reaction?
- A.
40 g of HCl in 1000 cm3 of water.
- B.
20 g of HCl in 1000 cm3 of water.
- C.
15 g of HCl in 500 cm3 of water.
- D.
10 g of HCl in 100 cm3 of water.
Correct Answer
D. 10 g of HCl in 100 cm3 of water.Explanation
The concentration of the hydrochloric acid affects the rate of reaction. Higher concentration means more hydrochloric acid particles are present in the solution, increasing the chances of collision with the magnesium atoms and leading to a faster reaction. Therefore, the solution with the highest concentration, which is 10 g of HCl in 100 cm3 of water, would give the fastest initial rate of reaction.Rate this question:
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- 4.
When an excess of calcium carbonate is added to dilute hydrochloric acid, the reactiongradually becomes slower and finally stops. Which statement best explains why this happens?
- A.
An insoluble layer of calcium chloride is formed on the calcium carbonate.
- B.
The pieces of calcium carbonate gradually become smaller.
- C.
The calcium carbonate is covered by bubbles of carbon dioxide.
- D.
The concentration of hydrochloric acid gradually reduces to zero.
Correct Answer
D. The concentration of hydrochloric acid gradually reduces to zero.Explanation
As the excess of calcium carbonate reacts with the hydrochloric acid, it produces carbon dioxide gas. This gas forms bubbles that adhere to the surface of the calcium carbonate, creating a layer that slows down the reaction. As the reaction progresses, the concentration of hydrochloric acid decreases as it is consumed, eventually reaching zero and causing the reaction to stop completely.Rate this question:
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- 5.
Under which of the following conditions will marble (calcium carbonate) react most rapidly with hydrochloric acid?
- A.
Marble chips and dilute acid at 40 degrees celsius.
- B.
Marble chips and concentrated acid at 20 degrees celsius.
- C.
Marble powder and dilute acid at 20 degrees celsius.
- D.
Marble powder and concentrated acid at 40 degrees celsius.
Correct Answer
D. Marble powder and concentrated acid at 40 degrees celsius.Explanation
Marble (calcium carbonate) will react most rapidly with hydrochloric acid when it is in the form of powder and the acid is concentrated, and the temperature is 40 degrees Celsius. The increased surface area of the marble powder allows for more contact between the reactants, leading to a faster reaction. Additionally, the higher concentration of the acid provides more reactant particles, increasing the likelihood of successful collisions and faster reaction rates. The higher temperature also increases the kinetic energy of the particles, resulting in more frequent and energetic collisions, further enhancing the reaction rate.Rate this question:
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- 6.
Copper(II) oxide catalyses the decomposition of aqueous hydrogen peroxide to give oxygen and water. In a laboratory experiment, aqueous hydrogen peroxide was shaken with copper(II) oxide in a test‑tube. What did the tube contain when the reaction was complete?
- A.
A black solid and a colourless liquid
- B.
A black solid and a blue liquid
- C.
A blue liquid only
- D.
A light blue solid and a colourless liquid
Correct Answer
A. A black solid and a colourless liquidExplanation
When the reaction between aqueous hydrogen peroxide and copper(II) oxide is complete, the tube would contain a black solid and a colorless liquid. This is because copper(II) oxide acts as a catalyst, speeding up the decomposition of hydrogen peroxide into oxygen and water. The black solid is the copper(II) oxide, which does not undergo any change during the reaction. The colorless liquid is the water that is formed as a product of the decomposition reaction.Rate this question:
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- 7.
If a strip of magnesium is dropped into excess hydrochloric acid, an exothermic reaction occurs. The rate of this reaction increases during the first few seconds because
- A.
The amount of magnesium is decreasing
- B.
The magnesium is acting as a catalyst
- C.
The solution is becoming hotter
- D.
The surface area of the magnesium is increasing
Correct Answer
C. The solution is becoming hotterExplanation
In an exothermic reaction, heat is released. When a strip of magnesium is dropped into excess hydrochloric acid, an exothermic reaction occurs, causing the solution to become hotter. This increase in temperature leads to an increase in the rate of the reaction during the first few seconds. As the solution gets hotter, the reactant molecules gain more kinetic energy, leading to more frequent and energetic collisions, which result in a faster reaction rate.Rate this question:
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- 8.
Why is nickel used in the hydrogenation of alkenes?
- A.
It increases the yield of the products.
- B.
It makes the reaction more exothermic (heat releasing).
- C.
It lowers the activation energy of the reaction.
- D.
It prevents a reverse reaction from occurring.
Correct Answer
C. It lowers the activation energy of the reaction.Explanation
Nickel is used in the hydrogenation of alkenes because it lowers the activation energy of the reaction. Activation energy is the minimum energy required for a reaction to occur. By lowering the activation energy, nickel catalysts facilitate the reaction by providing an alternative pathway with a lower energy barrier for the reactants to convert into products. This allows the reaction to proceed more easily and at lower temperatures, increasing the efficiency of the process.Rate this question:
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- 9.
Which of the following industrial processes does not use a catalyst?
- A.
The synthesis of ammonia
- B.
The fermentation of sugar
- C.
The oxidation of sulfur dioxide
- D.
The electrolysis of sodium chloride
Correct Answer
D. The electrolysis of sodium chlorideExplanation
The electrolysis of sodium chloride does not use a catalyst. Electrolysis is a process in which an electric current is passed through a solution to produce a chemical reaction. In the case of the electrolysis of sodium chloride, the solution is split into its constituent elements, sodium and chlorine, through the application of an electric current. This reaction does not require a catalyst to occur. In contrast, the synthesis of ammonia, fermentation of sugar, and oxidation of sulfur dioxide all involve chemical reactions that are facilitated by the presence of a catalyst.Rate this question:
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- 10.
A chemical reaction between a solid and an acid is too fast for safe use by a class of students. Which set of changes is most likely to make the reaction safe for the students to use?
- A.
Pieces of solid - larger; acid - less concentrated; temperature - lower
- B.
Pieces of solid - larger; acid - more concentrated; temperature - higher
- C.
Pieces of solid - smaller; acid - less concentrated; temperature - lower
- D.
Pieces of solid - smaller; acid - more concentrated; temperature - higher
Correct Answer
A. Pieces of solid - larger; acid - less concentrated; temperature - lowerExplanation
By increasing the size of the solid pieces, the surface area available for the reaction decreases, which slows down the reaction. Decreasing the concentration of the acid also slows down the reaction, as there are fewer acid particles available to react with the solid. Lowering the temperature further decreases the rate of the reaction. Therefore, by making these changes, the reaction becomes slower and safer for the students to use.Rate this question:
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Current Version
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Mar 21, 2023Quiz Edited by
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Mar 01, 2010Quiz Created by
Davincent
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