Topic 6 Flashcards
(15 cards)
What is the rate of a chemical reaction?
how fast the reactants are changing into products
Name some examples of slow reactions.
-rusting of iron
-chemical weathering - like acid rain damage to limestone buildings
Name an examples of moderate reaction.
metal magnesium reacting with an acid to produce a gentle stream of bubbles
Name some examples of fast reactions.
burning but explosions are even faster and release a lot of gas. Explosions are over in a fraction of a second.
What happens to particles in order for them to react.
Particles must collide with enough energy to react.
What does the rate of chemical reactions depend on?
-the collision frequency of reacting particles (how often they collide). The more collisions there are the faster the reaction is. e.g. doubling the frequency of collisions doubles the rate
-the energy transferred during a collision. Particles have to collide with enough energy for the collision to be succesful.
What does the rate of a reaction depend on?
-temperature
-the concentration of solution or the pressure of gas
-surface area
-the presence of a catalyst
What is the activation energy?
the minimum amount of energy that particles need to react. particles need this much energy to break the bonds in the reactants and start the reaction
how does temperature increasing increase the rate of the reaction?
When the temperature is increased, the particles all move faster. If they’re moving faster this means they are going to collide more frequently. Also the faster they move the more energy they have, so more of the collisions will have enough energy to make the reaction happen.
how does increasing the concentration or pressure increase the rate of reaction?
If a solution is made more concentrated, it means there are more particles knocking about in the same volume of water (or other solvent). Similarly, when the pressure of a gas is increased, it means that the same number of particles occupies a smaller space. This makes the collisions between the reactant particles more frequent.
how does increasing the surface are increase the rate of reaction?
If one of the reactants is a solid, then breaking it up into smaller pieces will increase its surface area to volume ratio. This means that for the same volume of the solid, the particles around it will have more area to work on - so there will be collisions more frequently.
how does using a catalyst increase the rate of reaction?
Catalyst work by decreasing the activation energy needed for the reaction to occur. They do this by providing an alternative reaction pathway with a lower activation energy.
What is the formula to calculate rate of reaction and what is the units?
rate of reaction = amount of reactant used or amount of
product formed
3
cm or g
_______________________________________
time (s)
3
rate of reaction = cm /s or g/s
How do you know what the unit of the amount of reactant used or formed is (in the rate of reaction formula)?
when the product or reactant is a gas you usually measure the
3
amount in cm . If it’s solid then you use g.
What are the different ways of measuring rate of reaction?
1)precipitation and colour change
2)change in mass (usually gas given off)
3)the volume of gas given off
