Rates of Reaction and Energy changes Flashcards
What is the rate of reaction?
How quickly a reaction happens.
How can the rate of reaction be observed?
Either by measuring how quickly the reactants are used up or how quickly the products are formed.
What is the formula for Average rate of reaction?
Amount of reactant used or amount of product formed/Time
What are the 3 different ways the rate of reaction can be measured?
Precipitation, Change in mass or Volume of gas given off.
Explain how the precipitation method works?
Works for any reaction where mixing two see-through solutions produces a precipitate, which clouds the solution.
Mix the two reactant solutions and put the flask on a piece of paper that has a mark on it.
Observe the mark through the mixture and measure how long it takes for the mark to be covered.
The faster the mark disappears…
(Precipitation method)
the faster the reaction.
Explain how the Change in mass method works?
You can measure the rate of reaction that produces a gas using a mass balance.
As the gas is released, the lost mass is easily measured on the balance.
How do you know when the reaction has finished?
(Change in mass method)
The reading on the balance stops changing.
The quicker the reading on the balance drops…
(Change in mass method)
the faster the reaction.
How can rate of reaction be measured by Volume of gas given off?
Involves the use of a gas syringe to measure the volume of gas given off.
The more gas given off during a set time interval…
(Volume of gas given off)
the faster the reaction.
How can you tell the reaction has finished?
(Volume of gas given off)
When no more gas is produced.
How do you calculate rate of reaction?
Product made/time OR
Reactant lost/time.
How would you calculate the Mean rate of reaction after a certain amount of time from a graph?
Find out the total volume of gas produced after the certain amount of time.
The substitute the values into the equation:
Mean rate of reaction = quantity of product formed/time.
How would you calculate the Actual rate of reaction at a specified time from a graph?
Draw a tangent to the curve at the specified time.
Construct a right angled triangle.
Calculate the gradient of the tangent using the equation:
Gradient = Change in Y/ Change in X.
What does the rate of a chemical reaction depend on?
(Collision Theory)
How often reacting particles collide.
The energy transferred during a collision.
The more successful collisions there are…
the faster the reaction is.
What is the Activation energy?
The minimum energy that particles need to react when they collide.
Particles need to collide with at least the activation energy for the collision to be successful.
Why does increasing the temperature quicken rate of reaction?
The particles move faster to have a higher chance of more collisions.
Particles have more energy so collide harder.
Why does increasing the concentration of a liquid quicken rate of reaction?
There are more liquid particles closer to each other increasing chance of collisions.
Why does increasing the pressure on gas particles quicken rate of reaction?
The particles are in a smaller volume so are more likely to collide.
Why does increasing the surface area of a solid quicken rate of reaction?
More solid area is exposed for more chance of collisions.
What is a Catalyst?
A substance which increases the rate of reaction without being chemically changed or used up in the reaction.
How do Catalysts lower activation energy?
Looking for a different pathway for the reaction, making it easier to break the old bonds.
