Kinetics, Equilibria And Redox Reactions Flashcards
How to calculate rate of reaction?
Amount of reactant used or product formed / time
Describe collision theory
Particles must collide at the right orientation with a correct speed and sufficient energy
Define activation energy
Minimum amount of kinetic energy that particles need to react
In a Maxwell Boltzmann distribution curve, what does the area under the curve represent?
Total number of molecules
Why does the Maxwell Boltzmann curve start at 0,0?
No molecules have zero energy
What does the peak of the Maxwell Boltzmann curve represent?
The most likely energy of any single molecule
Increasing the temperature makes reactions _____
Faster
As they have more activation energy so more frequent successful collisions
What happens to the shape of Maxwell Boltzmann curve when the temp is increased?
It shifts to the right
Increasing conc and pressure ______ the rate of reaction
Increases
Increasing conc means that particles are closer together so more frequent successful collisions
Increasing pressure is the same
How does a catalyst work?
Increases the rate of reaction by providing an alternate pathway and lowering activation energy
Chemically unchanged after the reaction
What are the different ways to measure reaction rates ?
Timing how long a precipitate takes to form.
1) You can use this method when the product is a precipitate which clouds a solution.
2) You watch a mark through the solution and time how long it takes to be obscured.
Measuring a decrease in mass.
1) When one or more of the products is a gas, you can measure the rate of formation using a mass balance.
2) As gas is given off, the mass of the reaction mixture decreases.
3) This method is accurate and easy to do. But it does release gas into the atmosphere, so it’s usually done in a fume cupboard.
Measuring the volume of gas given off.
1) This involves using a gas syringe to measure the volume of gas being produced.
2) You can only use this method when one or more of the products is a gas.
3) Gas syringes usually give volumes to the nearest 0.1 cm?, so this method is accurate.
How to carry out reaction between sodium thiosulfate and hydrochloric acid?
The an use the amount of time that if takes for the precipitate to forne as se measure of the rate of this reaction
1) Measure out fixed volumes of sodium thiosulfate and hydrochloric acid, using a measuring cylinder,
2) Use a water bath to gently heat both solutions to the desired temperature before you mix them.
3) Mix the solutions in a conical flask. Place the flask over a black cross which can be seen through the solution. Watch the black cross disappear through the cloudy sulfur and time how long it takes to go.
4) The reaction can be repeated for solutions at different temperatures. The depth of liguid must be kept the same each time. The concentrations of the solutions must also be kept the same.
5) The results should show that the higher the temperature, the faster the reaction rate and therefore the less time it takes for the mark to disappear.
Reversible reactions can reach _______ equilibrium
Dynamic
A dynamic equilibrium can only happen in a ______ system
Closed
What does Le Chateliers principle tell you?
If a reaction at equilibrium is subjected to a change in conc, pressure or temp, the posterior of equilibrium will move to counteract the change
