Define rate of reaction .

Rate of reaction is a measure of how quickly a reaction takes place, showing how fast reactants are converted into products.

What are the four factors that can affect the rate of a reaction?

The four factors that can affect the rate of a reaction are: Concentration of reactants in solution (or pressure of reacting gases) Temperature Surface area of solid reactants Presence of a catalyst

True or False? It is of economic interest to increase the rate of a reaction because a higher rate means a higher rate of production.

True. A higher rate of reaction means a higher rate of production , making the process more efficient and cost-effective.

In the sodium thiosulfate experiment, dilute hydrochloric acid is added to sodium thiosulfate solution. The reaction is timed until a cross drawn on paper beneath the flask can no longer be .......... from above.

In the sodium thiosulfate experiment, dilute hydrochloric acid is added to sodium thiosulfate solution. The reaction is timed until a cross drawn on paper beneath the flask can no longer be seen from above.

How is the effect of surface area on rate of reaction investigated using calcium carbonate?

The experiment uses calcium carbonate chips in dilute hydrochloric acid . Gas produced is collected in an inverted measuring cylinder over water. Different sizes of calcium carbonate chips are used and the volume of gas produced in a fixed time is compared.

True or False? The mass of a catalyst is less at the end of a reaction than at the start.

False. A catalyst speeds up a reaction without being used up. Its mass at the start and end of the reaction remains the same .

Complete the table to show the measurement used in each experiment. Variable tested Method Measurement Concentration Sodium thiosulfate + HCl, observe cross Surface area CaCO 3 chips + HCl, collect gas Temperature Mg strip in HCl at different temperatures

Variable tested Method Measurement Concentration Sodium thiosulfate + HCl, observe cross Time for cross to disappear Surface area CaCO 3 chips + HCl, collect gas Volume of gas in fixed time Temperature Mg strip in HCl at different temperatures Time for Mg to dissolve

How does the rate-of-reaction graph change when concentration is increased?

At higher concentration , the graph has a steeper gradient at the start and becomes horizontal sooner, but forms the same total amount of product as at lower concentration.

How is the effect of a catalyst on rate of reaction investigated using hydrogen peroxide?

Hydrogen peroxide is added to a conical flask with manganese(IV) oxide as the catalyst . The gas produced is collected in an inverted measuring cylinder over water. The experiment is repeated without the catalyst and the volumes of gas are compared.

What is collision theory ?

Collision theory states that chemical reactions occur when reactant particles collide with sufficient energy to break bonds and form products.

How does increasing the concentration of a solution increase the rate of reaction?

Increasing concentration means more reactant particles are present in a given volume. This leads to more frequent collisions per second, resulting in more successful collisions and a faster rate of reaction.

True or False? Doubling the number of particles in a solution doubles the number of collisions per second.

True. The number of collisions is proportional to the number of particles present. If particle count doubles, the collision rate also doubles.

Increasing the .......... of a gas increases the rate of reaction because the same number of particles are in a smaller .......... , leading to more collisions per second.

Increasing the pressure of a gas increases the rate of reaction because the same number of particles are in a smaller volume , leading to more collisions per second.

Why does increasing the temperature increase the rate of reaction?

Increasing temperature gives reactant particles more kinetic energy . This leads to more frequent collisions and more collisions with enough energy to be successful, so the rate of reaction increases.

True or False? Increasing temperature increases the rate of reaction because particles have more kinetic energy.

True. A higher temperature gives particles more kinetic energy . This means more particles have energy greater than or equal to the activation energy , so there are more successful collisions per second.

How does increasing the surface area of a solid reactant increase the rate of reaction?

Increasing surface area exposes more particles of the solid to the other reactant. This causes more frequent and successful collisions per second, increasing the rate of reaction.

Temperature affects reaction rate by increasing both the number of collisions and the .......... of the collisions, but the increase in .......... is the more important factor.

Temperature affects reaction rate by increasing both the number of collisions and the energy of the collisions, but the increase in energy is the more important factor.

What happens to the number of collisions per second if the surface area of a solid reactant is doubled?

If the surface area is doubled, the number of collisions per second also doubles. This is because twice as many solid particles are exposed to the other reactant.

A catalyst is a substance that speeds up the rate of a reaction without itself being altered or consumed.

How does a catalyst increase the rate of a reaction?

A catalyst provides an alternative reaction pathway that has a lower activation energy . This means more reactant particles have sufficient energy to collide successfully, increasing the rate.

True or False? A catalyst is permanently used up during a chemical reaction.

False. A catalyst is not consumed or altered during a reaction. Its mass at the start and end of the reaction is the same .

Catalysts do not form part of the chemical equation but are sometimes written above or below the .......... arrow.

Catalysts do not form part of the chemical equation but are sometimes written above or below the reaction arrow.

How much catalyst is typically needed to affect the rate of a reaction?

Only a small amount of catalyst is needed to have an effect. Because the catalyst is not consumed, it can continue to work throughout the reaction.

True or False? Transition metals are widely used as catalysts because they can form ions with different charges.

True. Transition metals can form ions with different charges, which means they can gain and lose electrons during reactions. This makes them effective catalysts.

Why is catalysis important in commercial chemical processes?

Catalysts increase the rate of reaction, which means a higher rate of production . They also reduce energy costs, making industrial processes more efficient and sustainable.

.......... act as catalysts in .......... systems, speeding up chemical reactions in living organisms.

Enzymes act as catalysts in biological systems, speeding up chemical reactions in living organisms.

What catalyst is used in the Haber process to make ammonia?

The Haber process uses an iron catalyst to speed up the reaction between nitrogen and hydrogen to produce ammonia (NH 3 ).

Define activation energy .

Activation energy is the minimum energy that reactant particles must have in order for a successful collision to occur and a reaction to take place.

What does a reaction profile show?

A reaction profile shows how the energy changes as a reaction progresses. It displays the relative energies of the reactants and products and the activation energy needed to start the reaction.

True or False? For an exothermic reaction, the value of ΔH is positive and the products are at a higher energy than the reactants.

False. For an exothermic reaction, the value of Δ H is negative and the arrow on the reaction profile points downwards. The products are at a lower energy than the reactants.

On a reaction profile, the initial rise in energy from the reactants to the .......... of the curve represents the .......... energy.

On a reaction profile, the initial rise in energy from the reactants to the peak of the curve represents the activation energy.

How does a catalyst affect the activation energy shown on a reaction profile?

A catalyst provides an alternative reaction pathway with a lower activation energy . On the reaction profile, this is shown as a lower peak. More molecules then have enough energy to react, increasing the rate.

True or False? Reactions with a low activation energy occur readily because little energy is needed to start them.

True. A low activation energy means that more particles have sufficient energy to collide successfully. The reaction therefore starts easily and proceeds at a faster rate.

How does the reaction profile of an endothermic reaction differ from an exothermic one?

In an endothermic reaction, the products are at a higher energy than the reactants and Δ H is positive . In an exothermic reaction, the products are lower in energy and Δ H is negative.

By lowering the activation energy, a catalyst means that a greater .......... of molecules in the reaction mixture have sufficient energy for an effective .......... .

By lowering the activation energy, a catalyst means that a greater proportion of molecules in the reaction mixture have sufficient energy for an effective collision .

What is the role of marble chips in this surface area experiment?

Marble chips ( calcium carbonate , CaCO 3 ) act as the solid reactant. By using different sizes of chips, the effect of surface area on the rate of reaction can be investigated.

What gas is produced when marble chips react with hydrochloric acid?

The gas produced is carbon dioxide (CO 2 ). This is formed when calcium carbonate reacts with dilute hydrochloric acid.

True or False? Smaller marble chips react faster than larger chips in the same amount of acid.

True. Smaller chips have a greater surface area , so more particles are exposed to the acid. This leads to more frequent and successful collisions , increasing the rate of reaction.

In the surface area experiment, marble chips are added to a conical flask containing .......... The gas produced is collected in an inverted .......... over water.

In the surface area experiment, marble chips are added to a conical flask containing hydrochloric acid . The gas produced is collected in an inverted measuring cylinder over water.

What conclusion can be drawn from the marble chips experiment about surface area and rate?

Increasing the surface area of the marble chips increases the rate of reaction . More particles are exposed to the acid, leading to more frequent and successful collisions.

Complete the table to show the expected trend in the marble chips experiment. Size of marble chip Expected volume of gas in 30 s Smallest chips Medium chips Largest chips

Size of marble chip Expected volume of gas in 30 s Smallest chips Largest Medium chips Intermediate Largest chips Smallest

What is hydrogen peroxide used for in this catalyst experiment?

Hydrogen peroxide is the reactant that decomposes in this experiment. Different catalysts are added to compare how quickly they speed up the decomposition reaction.

How is the rate compared for different catalysts in this experiment?

The volume of gas produced in a fixed time is measured for each catalyst. The results for different catalysts are plotted on the same graph and the rates compared.

True or False? In this experiment, only one type of catalyst is tested to investigate its effect on hydrogen peroxide.

False. The experiment tests several different catalysts , such as manganese(IV) oxide, lead(II) oxide, iron(III) oxide and copper(II) oxide, to compare their relative effectiveness.

In the catalyst experiment, hydrogen peroxide is added to a conical flask, a .......... is added and the bung is closed. The volume of .......... produced in a fixed time is measured.

In the catalyst experiment, hydrogen peroxide is added to a conical flask, a catalyst is added and the bung is closed. The volume of gas produced in a fixed time is measured.

How are the results of the different catalysts displayed in this experiment?

The data for each catalyst is plotted on the same graph so that the relative rates of reaction can be compared directly.

Name two catalysts that could be used in the catalytic decomposition of hydrogen peroxide experiment.

Two catalysts that could be used are: Manganese(IV) oxide Lead(II) oxide Iron(III) oxide and copper(II) oxide are also suitable options.

IGCSEChemistryEdexcelChemistry (Modular)Unit 2Flashcards7. Physical Chemistry: Part 2Rates of reaction

Rates of reaction (Edexcel IGCSE Chemistry (Modular): Unit 2): Flashcards

Exam code: 4XCH1

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FrontMeasuring Rates of Reactions
Define rate of reaction.
FrontMeasuring Rates of Reactions
What are the four factors that can affect the rate of a reaction?
BackMeasuring Rates of Reactions
The four factors that can affect the rate of a reaction are:
Concentration of reactants in solution (or pressure of reacting gases)
Temperature
Surface area of solid reactants
Presence of a catalyst

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Cards in this collection (47)

Define rate of reaction.
Rate of reaction is a measure of how quickly a reaction takes place, showing how fast reactants are converted into products.
What are the four factors that can affect the rate of a reaction?
The four factors that can affect the rate of a reaction are:
1. Concentration of reactants in solution (or pressure of reacting gases)
2. Temperature
3. Surface area of solid reactants
4. Presence of a catalyst
True or False?
It is of economic interest to increase the rate of a reaction because a higher rate means a higher rate of production.
True.
A higher rate of reaction means a higher rate of production, making the process more efficient and cost-effective.
In the sodium thiosulfate experiment, dilute hydrochloric acid is added to sodium thiosulfate solution. The reaction is timed until a cross drawn on paper beneath the flask can no longer be .......... from above.
In the sodium thiosulfate experiment, dilute hydrochloric acid is added to sodium thiosulfate solution. The reaction is timed until a cross drawn on paper beneath the flask can no longer be seen from above.
How is the effect of surface area on rate of reaction investigated using calcium carbonate?
The experiment uses calcium carbonate chips in dilute hydrochloric acid. Gas produced is collected in an inverted measuring cylinder over water. Different sizes of calcium carbonate chips are used and the volume of gas produced in a fixed time is compared.
True or False?
The mass of a catalyst is less at the end of a reaction than at the start.
False.
A catalyst speeds up a reaction without being used up. Its mass at the start and end of the reaction remains the same.

Complete the table to show the measurement used in each experiment.

Variable tested	Method	Measurement
Concentration	Sodium thiosulfate + HCl, observe cross
Surface area	CaCO₃ chips + HCl, collect gas
Temperature	Mg strip in HCl at different temperatures

Variable tested	Method	Measurement
Concentration	Sodium thiosulfate + HCl, observe cross	Time for cross to disappear
Surface area	CaCO₃ chips + HCl, collect gas	Volume of gas in fixed time
Temperature	Mg strip in HCl at different temperatures	Time for Mg to dissolve

How does the rate-of-reaction graph change when concentration is increased?
At higher concentration, the graph has a steeper gradient at the start and becomes horizontal sooner, but forms the same total amount of product as at lower concentration.
How is the effect of a catalyst on rate of reaction investigated using hydrogen peroxide?
Hydrogen peroxide is added to a conical flask with manganese(IV) oxide as the catalyst. The gas produced is collected in an inverted measuring cylinder over water. The experiment is repeated without the catalyst and the volumes of gas are compared.
What is collision theory?
Collision theory states that chemical reactions occur when reactant particles collide with sufficient energy to break bonds and form products.
How does increasing the concentration of a solution increase the rate of reaction?
Increasing concentration means more reactant particles are present in a given volume. This leads to more frequent collisions per second, resulting in more successful collisions and a faster rate of reaction.
True or False?
Doubling the number of particles in a solution doubles the number of collisions per second.
True.
The number of collisions is proportional to the number of particles present. If particle count doubles, the collision rate also doubles.
Increasing the .......... of a gas increases the rate of reaction because the same number of particles are in a smaller .........., leading to more collisions per second.
Increasing the pressure of a gas increases the rate of reaction because the same number of particles are in a smaller volume, leading to more collisions per second.
Why does increasing the temperature increase the rate of reaction?
Increasing temperature gives reactant particles more kinetic energy. This leads to more frequent collisions and more collisions with enough energy to be successful, so the rate of reaction increases.
True or False?
Increasing temperature increases the rate of reaction because particles have more kinetic energy.
True.
A higher temperature gives particles more kinetic energy. This means more particles have energy greater than or equal to the activation energy, so there are more successful collisions per second.
How does increasing the surface area of a solid reactant increase the rate of reaction?
Increasing surface area exposes more particles of the solid to the other reactant. This causes more frequent and successful collisions per second, increasing the rate of reaction.
Temperature affects reaction rate by increasing both the number of collisions and the .......... of the collisions, but the increase in .......... is the more important factor.
Temperature affects reaction rate by increasing both the number of collisions and the energy of the collisions, but the increase in energy is the more important factor.
What happens to the number of collisions per second if the surface area of a solid reactant is doubled?
If the surface area is doubled, the number of collisions per second also doubles. This is because twice as many solid particles are exposed to the other reactant.
Define catalyst.
A catalyst is a substance that speeds up the rate of a reaction without itself being altered or consumed.
How does a catalyst increase the rate of a reaction?
A catalyst provides an alternative reaction pathway that has a lower activation energy. This means more reactant particles have sufficient energy to collide successfully, increasing the rate.
True or False?
A catalyst is permanently used up during a chemical reaction.
False.
A catalyst is not consumed or altered during a reaction. Its mass at the start and end of the reaction is the same.
Catalysts do not form part of the chemical equation but are sometimes written above or below the .......... arrow.
Catalysts do not form part of the chemical equation but are sometimes written above or below the reaction arrow.
How much catalyst is typically needed to affect the rate of a reaction?
Only a small amount of catalyst is needed to have an effect. Because the catalyst is not consumed, it can continue to work throughout the reaction.
True or False?
Transition metals are widely used as catalysts because they can form ions with different charges.
True.
Transition metals can form ions with different charges, which means they can gain and lose electrons during reactions. This makes them effective catalysts.
Why is catalysis important in commercial chemical processes?
Catalysts increase the rate of reaction, which means a higher rate of production. They also reduce energy costs, making industrial processes more efficient and sustainable.
.......... act as catalysts in .......... systems, speeding up chemical reactions in living organisms.
Enzymes act as catalysts in biological systems, speeding up chemical reactions in living organisms.
What catalyst is used in the Haber process to make ammonia?
The Haber process uses an iron catalyst to speed up the reaction between nitrogen and hydrogen to produce ammonia (NH₃).
Define activation energy.
Activation energy is the minimum energy that reactant particles must have in order for a successful collision to occur and a reaction to take place.
What does a reaction profile show?
A reaction profile shows how the energy changes as a reaction progresses. It displays the relative energies of the reactants and products and the activation energy needed to start the reaction.
True or False?
For an exothermic reaction, the value of ΔH is positive and the products are at a higher energy than the reactants.
False.
For an exothermic reaction, the value of ΔH is negative and the arrow on the reaction profile points downwards. The products are at a lower energy than the reactants.
On a reaction profile, the initial rise in energy from the reactants to the .......... of the curve represents the .......... energy.
On a reaction profile, the initial rise in energy from the reactants to the peak of the curve represents the activation energy.
How does a catalyst affect the activation energy shown on a reaction profile?
A catalyst provides an alternative reaction pathway with a lower activation energy. On the reaction profile, this is shown as a lower peak. More molecules then have enough energy to react, increasing the rate.
True or False?
Reactions with a low activation energy occur readily because little energy is needed to start them.
True.
A low activation energy means that more particles have sufficient energy to collide successfully. The reaction therefore starts easily and proceeds at a faster rate.
How does the reaction profile of an endothermic reaction differ from an exothermic one?
In an endothermic reaction, the products are at a higher energy than the reactants and ΔH is positive. In an exothermic reaction, the products are lower in energy and ΔH is negative.
By lowering the activation energy, a catalyst means that a greater .......... of molecules in the reaction mixture have sufficient energy for an effective .......... .
By lowering the activation energy, a catalyst means that a greater proportion of molecules in the reaction mixture have sufficient energy for an effective collision.
What is the role of marble chips in this surface area experiment?
Marble chips (calcium carbonate, CaCO₃) act as the solid reactant. By using different sizes of chips, the effect of surface area on the rate of reaction can be investigated.
What gas is produced when marble chips react with hydrochloric acid?
The gas produced is carbon dioxide (CO₂). This is formed when calcium carbonate reacts with dilute hydrochloric acid.
True or False?
Smaller marble chips react faster than larger chips in the same amount of acid.
True.
Smaller chips have a greater surface area, so more particles are exposed to the acid. This leads to more frequent and successful collisions, increasing the rate of reaction.
In the surface area experiment, marble chips are added to a conical flask containing .......... The gas produced is collected in an inverted .......... over water.
In the surface area experiment, marble chips are added to a conical flask containing hydrochloric acid. The gas produced is collected in an inverted measuring cylinder over water.
What conclusion can be drawn from the marble chips experiment about surface area and rate?
Increasing the surface area of the marble chips increases the rate of reaction. More particles are exposed to the acid, leading to more frequent and successful collisions.
Complete the table to show the expected trend in the marble chips experiment.
Size of marble chip
Expected volume of gas in 30 s
Smallest chips
Medium chips
Largest chips
Size of marble chip
Expected volume of gas in 30 s
Smallest chips
Largest
Medium chips
Intermediate
Largest chips
Smallest
What is hydrogen peroxide used for in this catalyst experiment?
Hydrogen peroxide is the reactant that decomposes in this experiment. Different catalysts are added to compare how quickly they speed up the decomposition reaction.
How is the rate compared for different catalysts in this experiment?
The volume of gas produced in a fixed time is measured for each catalyst. The results for different catalysts are plotted on the same graph and the rates compared.
True or False?
In this experiment, only one type of catalyst is tested to investigate its effect on hydrogen peroxide.
False.
The experiment tests several different catalysts, such as manganese(IV) oxide, lead(II) oxide, iron(III) oxide and copper(II) oxide, to compare their relative effectiveness.
In the catalyst experiment, hydrogen peroxide is added to a conical flask, a .......... is added and the bung is closed. The volume of .......... produced in a fixed time is measured.
In the catalyst experiment, hydrogen peroxide is added to a conical flask, a catalyst is added and the bung is closed. The volume of gas produced in a fixed time is measured.
How are the results of the different catalysts displayed in this experiment?
The data for each catalyst is plotted on the same graph so that the relative rates of reaction can be compared directly.
Name two catalysts that could be used in the catalytic decomposition of hydrogen peroxide experiment.
Two catalysts that could be used are:
1. Manganese(IV) oxide
2. Lead(II) oxide
Iron(III) oxide and copper(II) oxide are also suitable options.

Size of marble chip	Expected volume of gas in 30 s
Smallest chips
Medium chips
Largest chips

Size of marble chip	Expected volume of gas in 30 s
Smallest chips	Largest
Medium chips	Intermediate
Largest chips	Smallest

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