When solid sodium thiosulfate reacts with dilute HCl, sulfur and sulfur dioxide gas are produced. Which of the following cannot alter the rate of this reaction?

the pressure applied to the reaction mixture

the particle size of sodium thiosulfate

the concentration of hydrochloric acid

the temperature of the reaction mixture

Which of the following acids will produce the fastest initial speed of reaction when 1.0 g of calcium carbonate is added to it? (Assume that the experiments are carried out at the same temperature)

50.0 cm3 of 1.0 mol/dm3 sulfuric acid

50.0 cm3 of 1.0 mol/dm3 nitric acid

50.0 cm3 of 1.0 mol/dm3 hydrochloric acid

100.0 cm3 of 1.0 mol/dm3 ethanoic acid

Which of the following statements is true of catalyst?

The mass of a catalyst before and after a chemical reaction is the same.

A catalyst increases the yield of a product in a chemical reaction.

A catalyst increases the speed of a reaction by lowering the enthalpy change of a chemical reaction.

Copper (II) oxide is a black solid. It catalyses the decomposition of hydrogen peroxide. Some hydrogen peroxide was shaken with copper (II) oxide in a test tube. When the reaction had stopped, the test tube contained

a black solid and a colourless solution

a black solid and a blue solution

a brown solid and a colourless solution

Which of the following solutions would give the greatest initial rate of reaction and largest volume of gas when reacted with 1.0 g of calcium carbonate?

50.0 cm3 of 2.0 mol/dm3 sulfuric acid

When an excess of calcium carbonate is added to dilute HCl, the reaction gradually becomes slower and finally stops. Which statement best explains why this happens?

The concentration of HCl gradually reduces to zero.

An insoluble layer of calicum chloride is formed on the calcium carbonate.

The pieces of calcium carbonate gradually become smaller.

The calcium carbonate is covered by bubbles of carbon dioxide.

When a piece of calcium metal is added to dilute hydrochloric acid, the reaction is seen to be faster after 60 seconds than after only 10 seconds. What could explain this observation ?

Heat is produced in the reaction, which raises the temperature and so increases the rate.

The piece of calcium is smaller at 60 seconds than at 10 seconds.

The concentration of the hydrochloric acid increases during the reaction.

The reaction is catalysed by hydrogen ions from the acid.

Aqueous hydrogen peroxide decomposes to give oxygen gas. Two experiments were carried out to measure the rate of production of oxygen gas from aqueous hydrogen peroxide. The following graph was obtained. Which of the following sets of solutions have been used?

Experiment I: 75 cm3 of 0.5 mol/dm3 hydrogen peroxide Experiment II: 25 cm3 of 1.0 mol/dm3 hydrogen peroxide

Experiment I: 75 cm3 of 1.0 mol/dm3 hydrogen peroxide; Experiment II: 50 cm3 of 1.0 mol/dm3 hydrogen peroxide

Experiment I: 25 cm3 of 1.0 mol/dm3 hydrogen peroxide Experiment II: 75 cm3 of 0.5 mol/dm3 hydrogen peroxide

Experiment I: 100 cm3 of 1.0 mol/dm3 hydrogen peroxide Experiment II: 50 cm3 of 1.0 mol/dm3 hydrogen peroxide

One way to monitor the rate of a reaction is to measure the loss of mass of the reactants over a period of time. Which of the following reaction's rate cannot be monitored using this method?

Reaction of copper (II) sulfate with aqueous sodium hydroxide

Decomposition of aqueous hydrogen peroxide

Reaction of copper (II) carbonate wtih dilute HCl

Rate Of Reaction

1.

When solid sodium thiosulfate reacts with dilute HCl, sulfur and sulfur dioxide gas are produced. Which of the following cannot alter the rate of this reaction?
- A.
  
  The particle size of sodium thiosulfate
- B.
  
  The concentration of hydrochloric acid
- C.
  
  The pressure applied to the reaction mixture
- D.
  
  The temperature of the reaction mixture
Correct Answer
C. The pressure applied to the reaction mixture

Explanation
The pressure applied to the reaction mixture cannot alter the rate of this reaction because pressure does not affect the rate of a reaction involving only solids and gases. In this reaction, the reactants are solid sodium thiosulfate and dilute HCl, and the products are sulfur and sulfur dioxide gas. The rate of the reaction is determined by factors such as the particle size of sodium thiosulfate, the concentration of hydrochloric acid, and the temperature of the reaction mixture, but not the pressure.

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2.

Which of the following acids will produce the fastest initial speed of reaction when 1.0 g of calcium carbonate is added to it? (Assume that the experiments are carried out at the same temperature)
- A.
  
  50.0 cm3 of 1.0 mol/dm3 nitric acid
- B.
  
  50.0 cm3 of 1.0 mol/dm3 sulfuric acid
- C.
  
  50.0 cm3 of 1.0 mol/dm3 hydrochloric acid
- D.
  
  100.0 cm3 of 1.0 mol/dm3 ethanoic acid
Correct Answer
B. 50.0 cm3 of 1.0 mol/dm3 sulfuric acid

Explanation
Sulfuric acid is the correct answer because it is a strong acid and can fully dissociate in water to produce a high concentration of hydrogen ions. This high concentration of hydrogen ions increases the reaction rate with calcium carbonate, resulting in a faster initial speed of reaction. Nitric acid is also a strong acid, but the volume is half of sulfuric acid, so the concentration of hydrogen ions is lower. Hydrochloric acid is also a strong acid, but the volume is the same as sulfuric acid, so the concentration of hydrogen ions is the same. Ethanoic acid is a weak acid, so it does not fully dissociate in water and has a lower concentration of hydrogen ions, resulting in a slower reaction rate.

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3
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3.

Which of the following statements is true of catalyst?
- A.
  
  A catalyst must be a compound.
- B.
  
  A catalyst increases the yield of a product in a chemical reaction.
- C.
  
  The mass of a catalyst before and after a chemical reaction is the same.
- D.
  
  A catalyst increases the speed of a reaction by lowering the enthalpy change of a chemical reaction.
Correct Answer
C. The mass of a catalyst before and after a chemical reaction is the same.

Explanation
A catalyst is a substance that increases the speed of a chemical reaction without being consumed in the process. This means that the mass of a catalyst remains unchanged before and after the reaction. It facilitates the reaction by providing an alternative pathway with lower activation energy, thus lowering the enthalpy change of the reaction. While a catalyst can be a compound, it can also be an element or a mixture of substances. However, the statement that a catalyst increases the yield of a product is not necessarily true, as its main function is to accelerate the reaction, not to affect the overall yield.

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4.

A catalyst increases the rate of a reaction by lowering the ______________ energy of a reaction.

Correct Answer
activation

Explanation
A catalyst increases the rate of a reaction by lowering the activation energy of a reaction. Activation energy is the energy required for a reaction to occur. By lowering this energy barrier, a catalyst allows the reactant molecules to more easily reach the transition state, where the reaction can take place. This results in a faster reaction rate.

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4
5.

Copper (II) oxide is a black solid. It catalyses the decomposition of hydrogen peroxide. Some hydrogen peroxide was shaken with copper (II) oxide in a test tube. When the reaction had stopped, the test tube contained
- A.
  
  A blue solution only
- B.
  
  A black solid and a blue solution
- C.
  
  A black solid and a colourless solution
- D.
  
  A brown solid and a colourless solution
Correct Answer
C. A black solid and a colourless solution

Explanation
When hydrogen peroxide is shaken with copper (II) oxide, a reaction occurs where copper (II) oxide acts as a catalyst. The black solid is the copper (II) oxide, which does not undergo any change during the reaction. The hydrogen peroxide decomposes into water and oxygen gas, resulting in a colorless solution. Therefore, the test tube contains both the black solid (copper (II) oxide) and a colorless solution (water).

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2
0
6.

Which of the following solutions would give the greatest initial rate of reaction and largest volume of gas when reacted with 1.0 g of calcium carbonate?
- A.
  
  50.0 cm3 of 2.0 mol/dm3 sulfuric acid
- B.
  
  50.0 cm3 of 2.0 mol/dm3 HCl
- C.
  
  100 cm3 of 1.5 mol/dm3 HCl
- D.
  
  25.0 cm3 of 2.5 mol/dm3 HCl
Correct Answer
D. 25.0 cm3 of 2.5 mol/dm3 HCl

Explanation
The initial rate of a reaction is determined by the concentration of the reactants. The higher the concentration, the faster the reaction will proceed initially. In this case, the solution with 25.0 cm3 of 2.5 mol/dm3 HCl has the highest concentration of HCl, making it the solution that would give the greatest initial rate of reaction. The volume of gas produced is not directly related to the initial rate of reaction, but rather the stoichiometry of the reaction. Therefore, the volume of gas produced cannot be determined solely based on the given information.

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1
1
7.

When an excess of calcium carbonate is added to dilute HCl, the reaction gradually becomes slower and finally stops. Which statement best explains why this happens?
- A.
  
  An insoluble layer of calicum chloride is formed on the calcium carbonate.
- B.
  
  The concentration of HCl gradually reduces to zero.
- C.
  
  The pieces of calcium carbonate gradually become smaller.
- D.
  
  The calcium carbonate is covered by bubbles of carbon dioxide.
Correct Answer
B. The concentration of HCl gradually reduces to zero.

Explanation
When an excess of calcium carbonate is added to dilute HCl, the reaction gradually becomes slower and finally stops. This is because the calcium carbonate reacts with the HCl to form calcium chloride and carbon dioxide gas. As the reaction progresses, the concentration of HCl gradually reduces to zero as it is completely consumed by the reaction with calcium carbonate. This decrease in concentration of HCl leads to a decrease in the rate of reaction until it eventually stops when all the HCl is used up.

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1
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8.

When a piece of calcium metal is added to dilute hydrochloric acid, the reaction is seen to be faster after 60 seconds than after only 10 seconds. What could explain this observation ?
- A.
  
  The piece of calcium is smaller at 60 seconds than at 10 seconds.
- B.
  
  The concentration of the hydrochloric acid increases during the reaction.
- C.
  
  The reaction is catalysed by hydrogen ions from the acid.
- D.
  
  Heat is produced in the reaction, which raises the temperature and so increases the rate.
Correct Answer
D. Heat is produced in the reaction, which raises the temperature and so increases the rate.

Explanation
The observation can be explained by the fact that heat is produced in the reaction, which raises the temperature. An increase in temperature generally leads to an increase in the rate of a chemical reaction. Therefore, after 60 seconds, when more heat has been produced, the temperature is higher, resulting in a faster reaction compared to the initial 10 seconds.

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1
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9.

Aqueous hydrogen peroxide decomposes to give oxygen gas. Two experiments were carried out to measure the rate of production of oxygen gas from aqueous hydrogen peroxide. The following graph was obtained. Which of the following sets of solutions have been used?
- A.
  
  Experiment I: 75 cm3 of 1.0 mol/dm3 hydrogen peroxide; Experiment II: 50 cm3 of 1.0 mol/dm3 hydrogen peroxide
- B.
  
  Experiment I: 75 cm3 of 0.5 mol/dm3 hydrogen peroxide Experiment II: 25 cm3 of 1.0 mol/dm3 hydrogen peroxide
- C.
  
  Experiment I: 25 cm3 of 1.0 mol/dm3 hydrogen peroxide Experiment II: 75 cm3 of 0.5 mol/dm3 hydrogen peroxide
- D.
  
  Experiment I: 100 cm3 of 1.0 mol/dm3 hydrogen peroxide Experiment II: 50 cm3 of 1.0 mol/dm3 hydrogen peroxide
Correct Answer
B. Experiment I: 75 cm3 of 0.5 mol/dm3 hydrogen peroxide Experiment II: 25 cm3 of 1.0 mol/dm3 hydrogen peroxide

Explanation
The correct answer is Experiment I: 75 cm3 of 0.5 mol/dm3 hydrogen peroxide and Experiment II: 25 cm3 of 1.0 mol/dm3 hydrogen peroxide. This is because the graph shows that the rate of production of oxygen gas is higher in Experiment I compared to Experiment II. This suggests that the concentration of hydrogen peroxide is higher in Experiment I. Additionally, the volume of hydrogen peroxide used is also higher in Experiment I, further supporting this explanation.

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2
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10.

One way to monitor the rate of a reaction is to measure the loss of mass of the reactants over a period of time. Which of the following reaction's rate cannot be monitored using this method?
- A.
  
  Decomposition of aqueous hydrogen peroxide
- B.
  
  Reaction of Mg with dilute HCl
- C.
  
  Reaction of copper (II) sulfate with aqueous sodium hydroxide
- D.
  
  Reaction of copper (II) carbonate wtih dilute HCl
Correct Answer
C. Reaction of copper (II) sulfate with aqueous sodium hydroxide

Explanation
The reaction of copper (II) sulfate with aqueous sodium hydroxide cannot be monitored by measuring the loss of mass of the reactants over a period of time because this reaction does not involve the loss of mass. Instead, it involves a precipitation reaction where a solid (copper (II) hydroxide) is formed. Therefore, the change in mass cannot be used to monitor the rate of this reaction.

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