22 Questions
What is the role of catalysts in a reaction?
Increase the rate of reaction by lowering the activation energy
Why are catalysts not included in the reaction equation?
Because they remain unchanged throughout the reaction
How do catalysts affect the activation energy of a reaction?
Lower the activation energy
Which statement is true about enzymes acting as catalysts in biological systems?
Enzymes speed up reactions in biological systems
What happens to the rate of a reaction when a catalyst is present?
The rate increases
Why do more particles have energy greater than the activation energy when a catalyst is present?
Because catalysts provide an alternative pathway with lower activation energy
How does increasing the concentration of reacting solutions affect the rate of reaction?
Increases the rate by increasing collision frequency
What effect does increasing the pressure of reacting gases have on the rate of reaction?
Increases the rate by enhancing collision frequency
How does a greater surface area to volume ratio of a solid affect the rate of reaction?
Increases the rate by providing more surfaces for reactions to occur on
What are catalysts?
Substances that speed up reactions without being consumed
Which factor related to reacting solids affects the rate of reaction?
Surface area to volume ratio
What happens to catalysts during a chemical reaction?
They remain unchanged and can be reused
What can be used to measure the rate of reaction by recording the total volume of gas collected at regular intervals?
Burette
What units may be used to express the rate of reaction?
m/s
What does the gradient of a rate of reaction graph represent?
Rate of reaction
How does increasing temperature affect the rate of reaction?
Increases the rate of reaction
In terms of frequency and energy of collision between particles, what effect does an increase in pressure have on the rate of reaction?
Increases both frequency and energy of collisions
What would be the most appropriate unit to measure the amount of product formed over time?
$mol/s$
How is the rate of reaction calculated when using the volume of gas produced as a measure?
$volume-of-gas/time$
Which factor does NOT typically increase the rate of reaction?
Decreased concentration
'1/t is proportional to rate and gradients of graphs' implies what relationship between time and rate?
$t imes Rate = k$
What effect does increasing the surface area have on the rate of reaction?
$Increases$
Study Notes
Catalysts in Reactions
- Catalysts are substances that increase the rate of a reaction without being consumed or altered in the process.
- They are not included in the reaction equation because they are not reactants or products.
- Catalysts lower the activation energy required for a reaction to occur, allowing more particles to react.
Enzymes as Catalysts
- Enzymes are biological molecules that act as catalysts, increasing the rate of reactions in biological systems.
- They are highly specific, meaning each enzyme only catalyzes one specific reaction.
Effect of Catalysts on Reaction Rate
- When a catalyst is present, the rate of a reaction increases.
- This is because more particles have energy greater than the activation energy, allowing them to react.
Factors Affecting Reaction Rate
- Increasing the concentration of reacting solutions increases the rate of reaction.
- Increasing the pressure of reacting gases increases the rate of reaction by increasing the frequency and energy of collisions between particles.
- A greater surface area to volume ratio of a solid increases the rate of reaction by providing more sites for reaction to occur.
Measuring Reaction Rate
- The rate of reaction can be measured by recording the total volume of gas collected at regular intervals using a gas syringe.
- The rate of reaction can be expressed in units such as mol/L/s or cm³/s.
- The gradient of a rate of reaction graph represents the rate of reaction.
Temperature and Reaction Rate
- Increasing the temperature increases the rate of reaction by increasing the energy of particles and the frequency of collisions.
Calculating Reaction Rate
- When using the volume of gas produced as a measure, the rate of reaction can be calculated by dividing the volume of gas produced by the time taken.
Factors Not Affecting Reaction Rate
- Increasing the volume of the reaction vessel does not typically increase the rate of reaction.
Time and Rate Relationship
- The relationship between time and rate is inverse, meaning that as time increases, the rate of reaction decreases.
This quiz covers the identification of catalysts in reactions, and explains how catalysts work by lowering activation energy and providing an alternative pathway for the reaction to occur. Catalysts remain unchanged throughout the reaction and are not included in the reaction equation.
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