True or False? All collisions between reactant particles lead to a chemical reaction.

False. Most collisions are unsuccessful because the particles do not have enough energy. Only collisions where particle energy is greater than or equal to the activation energy result in a reaction.

What is collision theory ?

Collision theory states that for a reaction to occur, particles must collide with each other and the collision must have energy greater than or equal to the activation energy. Collisions that meet this requirement are called successful collisions.

For a reaction to occur, colliding particles must have energy greater than or equal to the ______ energy. Collisions that result in a reaction are called ______ collisions.

For a reaction to occur, colliding particles must have energy greater than or equal to the activation energy. Collisions that result in a reaction are called successful collisions.

True or False? Activation energy ( E a ) is the maximum energy that colliding particles must have in order to react.

False. Activation energy is the minimum energy that particles must have to react. Particles that collide with less than this energy do not react and simply bounce off each other.

Unsuccessful collisions occur when particles collide with energy ______ than the activation energy. The particles simply ______ off each other.

Unsuccessful collisions occur when particles collide with energy less than the activation energy. The particles simply bounce off each other.

What five conditions can be changed to increase the rate of a chemical reaction?

Increasing concentration or pressure (more particles per unit volume), increasing temperature (more particles have energy ≥ E a ), increasing the surface area of a solid reactant, and using a suitable catalyst. Each change results in more successful collisions per unit time.

The rate of a chemical reaction depends on the number of ______ ______ per unit time.

The rate of a chemical reaction depends on the number of successful collisions per unit time.

What does a catalyst do?

A catalyst speeds up the rate of a reaction without being used up. It provides an alternative reaction pathway with a lower activation energy, so a higher proportion of particles have enough energy to react successfully.

Increasing the concentration of a solution increases the rate of reaction because there are more particles per ______ volume, causing more frequent ______ .

Increasing the concentration of a solution increases the rate of reaction because there are more particles per unit volume, causing more frequent collisions .

True or False? The main reason a higher temperature increases the rate of a reaction is that particles collide more frequently.

False. The main reason is that particles have more kinetic energy , so a higher proportion of collisions have energy greater than or equal to the activation energy. More collisions are successful , not just more frequent.

A catalyst lowers the ______ energy of a reaction, meaning a ______ proportion of particles have enough energy to react.

A catalyst lowers the activation energy of a reaction, meaning a higher proportion of particles have enough energy to react.

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

A greater surface area means more of the solid is exposed to the other reactant. This allows more collisions per second between reactant particles, so the rate of reaction increases.

Increasing temperature gives particles more ______ energy. A greater proportion of collisions then have energy greater than or equal to the ______ energy, so more collisions are successful.

Increasing temperature gives particles more kinetic energy. A greater proportion of collisions then have energy greater than or equal to the activation energy, so more collisions are successful.

Why does increasing the pressure of a gas increase the rate of a reaction?

Increasing pressure means the same number of gas particles occupy a smaller volume, so there are more particles per unit volume. This increases the frequency of collisions, leading to more successful collisions per second and a higher rate of reaction.

Decreasing the temperature slows the rate of a reaction because particles have less ______ energy, so fewer collisions reach the ______ energy threshold.

Decreasing the temperature slows the rate of a reaction because particles have less kinetic energy, so fewer collisions reach the activation energy threshold.

Why does decreasing the concentration of a solution (or the pressure of a gas) slow the rate of a reaction?

There are fewer particles per unit volume, so collisions between reactant particles are less frequent. Fewer successful collisions occur per second, so the rate of reaction decreases.

Name three methods that can be used to measure the rate of a chemical reaction in the laboratory.

Measuring the loss in mass on a balance. Measuring the volume of gas produced using downward displacement or a gas syringe. Measuring the time for a colour change to occur.

In the sodium thiosulfate experiment, the reaction is timed until a ______ drawn beneath the flask can no longer be ______ from above.

In the sodium thiosulfate experiment, the reaction is timed until a cross drawn beneath the flask can no longer be seen from above.

True or False? Measuring loss in mass on a balance is suitable for investigating the rate of a reaction that produces hydrogen gas.

False. Hydrogen has a very low relative formula mass ( M r ), so the loss in mass is too small to measure accurately. The mass loss method is not suitable for gases with a small M r .

Gas collected during a rate experiment can be measured using ______ displacement of water or using a ______ syringe.

Gas collected during a rate experiment can be measured using downward displacement of water or using a gas syringe.

Why is cotton wool placed in the flask opening when measuring the rate of a reaction by loss in mass?

Cotton wool allows gas to escape from the flask so that mass loss can be measured, while preventing any solid or liquid from being ejected during a vigorous reaction.

To investigate the effect of temperature on rate of reaction, variables such as ______ and ______ area must be kept ______ .

To investigate the effect of temperature on rate of reaction, variables such as concentration and surface area must be kept constant .

True or False? Using powdered calcium carbonate instead of lumps produces a faster rate of reaction with hydrochloric acid, even when the mass used is the same.

True. Powdered calcium carbonate has a greater surface area than lumps of the same mass. More surface is exposed to the acid, so collisions are more frequent and the rate increases.

On a graph of volume of gas produced against time in a rate experiment, what does it mean when the curve becomes horizontal?

The curve becomes horizontal when the reaction has stopped. This happens when one of the reactants has been completely used up, so no more product can form.

On a rate of reaction graph, the ______ the gradient of the curve, the ______ the rate of reaction.

On a rate of reaction graph, the steeper the gradient of the curve, the faster the rate of reaction.

True or False? In a gas collection rate experiment, the reaction that produces the greatest total volume of gas is always the fastest.

False. The total volume of gas shows how much product forms, not the rate. The rate is shown by the steepness of the curve, particularly at the start of the reaction.

To find the rate of reaction at a specific point on a curve, draw a ______ to the curve at that point and calculate the ______ of that line.

To find the rate of reaction at a specific point on a curve, draw a tangent to the curve at that point and calculate the gradient of that line.

True or False? Increasing the amount of the limiting reactant in a rate experiment increases the total amount of product formed.

True. The limiting reactant determines how much product can form. Increasing it means more product is produced, so the curve reaches a higher maximum before levelling off.

If the amount of the reactant in ______ is increased, the total amount of product formed stays the ______ .

If the amount of the reactant in excess is increased, the total amount of product formed stays the same .

Why is the rate of reaction fastest at the very start of a reaction?

At the start, the concentration of reactants is at its highest, so particles are most crowded and collisions are most frequent. As the reaction proceeds, reactants are used up, collisions become less frequent and the rate decreases.

O LevelChemistryCambridge (CIE)Flashcards6. Chemical Reactions6.2 Rate of Reaction

6.2 Rate of Reaction (Cambridge (CIE) O Level Chemistry): Flashcards

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FrontCollision Theory
True or False?
All collisions between reactant particles lead to a chemical reaction.

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Cards in this collection (30)

True or False?
All collisions between reactant particles lead to a chemical reaction.
False.
Most collisions are unsuccessful because the particles do not have enough energy. Only collisions where particle energy is greater than or equal to the activation energy result in a reaction.
What is collision theory?
Collision theory states that for a reaction to occur, particles must collide with each other and the collision must have energy greater than or equal to the activation energy. Collisions that meet this requirement are called successful collisions.
For a reaction to occur, colliding particles must have energy greater than or equal to the ______ energy. Collisions that result in a reaction are called ______ collisions.
For a reaction to occur, colliding particles must have energy greater than or equal to the activation energy. Collisions that result in a reaction are called successful collisions.
True or False?
Activation energy (E_a) is the maximum energy that colliding particles must have in order to react.
False.
Activation energy is the minimum energy that particles must have to react. Particles that collide with less than this energy do not react and simply bounce off each other.
Unsuccessful collisions occur when particles collide with energy ______ than the activation energy. The particles simply ______ off each other.
Unsuccessful collisions occur when particles collide with energy less than the activation energy. The particles simply bounce off each other.
What five conditions can be changed to increase the rate of a chemical reaction?
Increasing concentration or pressure (more particles per unit volume), increasing temperature (more particles have energy ≥ E_a), increasing the surface area of a solid reactant, and using a suitable catalyst. Each change results in more successful collisions per unit time.
The rate of a chemical reaction depends on the number of ______ ______ per unit time.
The rate of a chemical reaction depends on the number of successful collisions per unit time.
What does a catalyst do?
A catalyst speeds up the rate of a reaction without being used up. It provides an alternative reaction pathway with a lower activation energy, so a higher proportion of particles have enough energy to react successfully.
Increasing the concentration of a solution increases the rate of reaction because there are more particles per ______ volume, causing more frequent ______.
Increasing the concentration of a solution increases the rate of reaction because there are more particles per unit volume, causing more frequent collisions.
True or False?
The main reason a higher temperature increases the rate of a reaction is that particles collide more frequently.
False.
The main reason is that particles have more kinetic energy, so a higher proportion of collisions have energy greater than or equal to the activation energy. More collisions are successful, not just more frequent.
A catalyst lowers the ______ energy of a reaction, meaning a ______ proportion of particles have enough energy to react.
A catalyst lowers the activation energy of a reaction, meaning a higher proportion of particles have enough energy to react.
Why does increasing the surface area of a solid reactant increase the rate of a reaction?
A greater surface area means more of the solid is exposed to the other reactant. This allows more collisions per second between reactant particles, so the rate of reaction increases.
Increasing temperature gives particles more ______ energy. A greater proportion of collisions then have energy greater than or equal to the ______ energy, so more collisions are successful.
Increasing temperature gives particles more kinetic energy. A greater proportion of collisions then have energy greater than or equal to the activation energy, so more collisions are successful.
Why does increasing the pressure of a gas increase the rate of a reaction?
Increasing pressure means the same number of gas particles occupy a smaller volume, so there are more particles per unit volume. This increases the frequency of collisions, leading to more successful collisions per second and a higher rate of reaction.
Decreasing the temperature slows the rate of a reaction because particles have less ______ energy, so fewer collisions reach the ______ energy threshold.
Decreasing the temperature slows the rate of a reaction because particles have less kinetic energy, so fewer collisions reach the activation energy threshold.
Why does decreasing the concentration of a solution (or the pressure of a gas) slow the rate of a reaction?
There are fewer particles per unit volume, so collisions between reactant particles are less frequent. Fewer successful collisions occur per second, so the rate of reaction decreases.
Name three methods that can be used to measure the rate of a chemical reaction in the laboratory.
1. Measuring the loss in mass on a balance.
2. Measuring the volume of gas produced using downward displacement or a gas syringe.
3. Measuring the time for a colour change to occur.
In the sodium thiosulfate experiment, the reaction is timed until a ______ drawn beneath the flask can no longer be ______ from above.
In the sodium thiosulfate experiment, the reaction is timed until a cross drawn beneath the flask can no longer be seen from above.
True or False?
Measuring loss in mass on a balance is suitable for investigating the rate of a reaction that produces hydrogen gas.
False.
Hydrogen has a very low relative formula mass (M_r), so the loss in mass is too small to measure accurately. The mass loss method is not suitable for gases with a small M_r.
Gas collected during a rate experiment can be measured using ______ displacement of water or using a ______ syringe.
Gas collected during a rate experiment can be measured using downward displacement of water or using a gas syringe.
Why is cotton wool placed in the flask opening when measuring the rate of a reaction by loss in mass?
Cotton wool allows gas to escape from the flask so that mass loss can be measured, while preventing any solid or liquid from being ejected during a vigorous reaction.
To investigate the effect of temperature on rate of reaction, variables such as ______ and ______ area must be kept ______.
To investigate the effect of temperature on rate of reaction, variables such as concentration and surface area must be kept constant.
True or False?
Using powdered calcium carbonate instead of lumps produces a faster rate of reaction with hydrochloric acid, even when the mass used is the same.
True.
Powdered calcium carbonate has a greater surface area than lumps of the same mass. More surface is exposed to the acid, so collisions are more frequent and the rate increases.
On a graph of volume of gas produced against time in a rate experiment, what does it mean when the curve becomes horizontal?
The curve becomes horizontal when the reaction has stopped. This happens when one of the reactants has been completely used up, so no more product can form.
On a rate of reaction graph, the ______ the gradient of the curve, the ______ the rate of reaction.
On a rate of reaction graph, the steeper the gradient of the curve, the faster the rate of reaction.
True or False?
In a gas collection rate experiment, the reaction that produces the greatest total volume of gas is always the fastest.
False.
The total volume of gas shows how much product forms, not the rate. The rate is shown by the steepness of the curve, particularly at the start of the reaction.
To find the rate of reaction at a specific point on a curve, draw a ______ to the curve at that point and calculate the ______ of that line.
To find the rate of reaction at a specific point on a curve, draw a tangent to the curve at that point and calculate the gradient of that line.
True or False?
Increasing the amount of the limiting reactant in a rate experiment increases the total amount of product formed.
True.
The limiting reactant determines how much product can form. Increasing it means more product is produced, so the curve reaches a higher maximum before levelling off.
If the amount of the reactant in ______ is increased, the total amount of product formed stays the ______.
If the amount of the reactant in excess is increased, the total amount of product formed stays the same.
Why is the rate of reaction fastest at the very start of a reaction?
At the start, the concentration of reactants is at its highest, so particles are most crowded and collisions are most frequent. As the reaction proceeds, reactants are used up, collisions become less frequent and the rate decreases.

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