Chemistry Unit 6 Flashcards
Kinetics (62 cards)
What is rate the reciprocal of?
Time
In a chemical reaction, as the concentration of the reactants decrease, the concentration of the products _______
Increase
When is the rate the greatest, and why is it then?
It is greatest at the start of a reaction because the concentration of the reactants is at its highest
Why would a graph showing the concentration of the products/reactants versus time plateau after a little while?
The reaction hits equilibrium and the concentrations are constant
List the five main ways to measure the rate of a reaction in a lab
- Change in volume of gas produced
- Change in mass
- Color change (spectrophotometer)
- Change in concentration
- Clock reaction
What are the two ways to measure a change in volume of gas produced?
- Use gas syringe to collect gas being produced at regular time intervals
- Collect gas over water (displacement), gas must have low solubility
What must be present in order to measure the change in volume of gas produced?
One product must be a gas
What are the two ways to measure change in concentration?
- Titration
- Conductivity - ions and charge allow for a solution to conduct
Does a decrease in number of ions mean a decrease or increase in conductivity?
Less ions means less conductivity!
What three things are listed in the collision theory?
- Particles must collide
- Particles must collide with appropriate orientation so that the reactive parts of the particles come into contact with each other
- Particles must collide with enough energy to react
Define Maxwell Boltzman Distribution and what it shows
The moving particles of a liquid or gas are not moving with the same velocity, some are moving faster and others slower. The faster they move the more kinetic energy they have. The Maxwell Boltzman Distribution shows the kinetic energy of particles
What does the area under the curve represent in a Maxwell Boltzman Distribution?
The area represents the number of particles with enough energy to react. As temp increases, the number of particles stays the same but the number of particles with more kinetic energy increases, which is why the higher temperature has a greater area.
How does the temperature affect the rate of a reaction?
Higher temperature = more particles with more kinetic energy = more effective collisions = faster rate
The rate of the reaction doubles for about every ___ degrees celsius the temp increases
10
How does the surface area affect the rate of a reaction?
More surface area = more places for collisions = faster rate
How does concentration affect the rate of a reaction?
Higher concentration = more particles to collide = faster reaction rate
What causes the initial rate of a reaction to be faster?
A greater concentration because there are more particles to collide.
If they have the same number of moles but one has a greater concentration, they will start apart but end at the same spot
As the reaction happens does the concentration of the reactants increase or decrease?
Decrease
If the two reactions have different numbers of moles of reactants, will they end at the same spot?
No, the one with more moles will be greater
How does a catalyst affect the rate of a reaction?
A catlyst increases the rate of a reaction by providing an alternative pathway
Does a catalyst cause a reaction to need more or less activation energy?
Less!
Is the catalyst ever seen in a reaction?
No!
Does a catalyst change the heat of reaction?
No!
Define reaction mechanisms
A series of simple steps involved in a reaction
