The Rate and Extent of Chemical Change Flashcards
What’s the rate of reaction?
How fast reactants turn to products
What’s the equation for the rate of reaction?
the amount of reactants used/ products formed divided by time
What’s the slowest and fastest reaction?
Slowest: iron rusting
Fastest: an explosion
How to know how fast a reaction is with a graph?
The steeper the line, the faster the reaction
The fastest reactions are very steep and become flat in the shortest amount of time.
What’s the collision theory?
Reactant particles must collide with each other
They must collide with the minimum energy, activation energy, to react
What are the factors affecting the rate of reaction and how does each one do so?
HINT: Can’t Stand Chemistry Teachers, Period
Concentration (increasing):
Increasing the concentration of the solution means there are more particles are in the same volume of the solution and this makes collisions more frequent, meaning more collisions will be successful.
Surface Area (increasing): When you break down a solid, the SA:V ratio increases and more particles are exposed to the reactant and collisions will take place more frequently.
Catalyst (adding):
When you add a catalyst, it decreases the activation energy so more particles are able to collide successfully
Temperature (increasing):
When you increase the temperature, the particles gain more kinetic energy and start moving faster so they start colliding more frequently and there’ll be more successful collisions. Also, the particles will have the activation energy or more so more collisions will have enough energy to successfully collide.
Pressure (increasing):
Increasing the pressure of the gas means there are more particles are in the same volume and this makes collisions more frequent, meaning more collisions will be successful.
How do you calculate mean reaction rate between two time intervals and at a particular point of time?
- Work out the overall change in the y-value and divide it by the total time taken.
- Draw a tangent and calculate the gradient of the tangent.
What are the three ways we can measure the rate of an reaction?
Precipitation:
• Mix two reactants solutions in a flask and put the flask on a paper with a cross.
• As the reaction takes place, the solution will get cloudy and it will become harder to see the cross.
• Measure how long it takes for the cross to disappear; the faster it disappears, the faster the reaction
• NOT EVERYONE WILL AGREE ON THE SAME POINT
(can use this experiment to see how temperature affects the rate of reaction)
Change in Mass:
• Put the flask on a balance and start the reaction.
• As the gas is released, the faster the reaction.
• The reaction’s done when the mass stops changing.
• Plot a graph with the results (change in mass against time)
• GAS BEING RELEASING CAN BE HARMFUL SO DO EXPERIMENT IN A FUME CUPBOARD
(can use this reaction to see how surface area and concentration affect the rate of reaction)
Change in Volume:
• Collect the gas given off using a gas syringe.
• The more gas given off, the faster the reaction.
• The reaction’s done when no more gas is being given off.
• Plot a graph with your results (gas volume against time)
• USE THE RIGHT SIZE GAS SYRINGE AS THE ONE CAN BLOW OFF
(can use this experiment to see how surface area affect the rate of reaction)
What are reversible reactions?
Reactions that can go forward as well as backwards.
What happens in a reversible reaction?
As particles react, their concentrations falls, slowing the forward reaction down but as more products being made, the concentration rises and the backward reaction speeds up.
Soon, they’ll be happening at the same rate - the system’s at equilibrium. This means the concentrations of the products and the reactants will be the same and there’s no change.
This only happens in a closed system where nothing can enter or escape.
What’s another word to use instead of cloudiness?
Turbidity
What’s the experiment of magnesium and hydrochloric acid?
Add a set volume of hydrochloric acid in a conical flask, then add a magnesium ribbon to the acid.
Attach a gas syringe to the flask and start a stopwatch.
Then measure the volume of gas at regular time intervals.
Then you can plot a graph of time and the volume of gas.
What’s the experiment of sodium thiosulfate and hydrochloric acid?
Add a set volume of dilute sodium thiosulfate in a conical flask
Place the flask on a piece of paper with a black cross.
Add dilute hydrochloric acid to the flask and start a stopwatch.
Then measure the volume of gas at regular time intervals.
Time how long it takes for the cross to disappear.
What does it mean to say the equilibrium lies on the right?
It means the concentration of products is more than the reactants.
What does the position of equilibrium depend on?
Temperature, concentration, pressure
