C6 Rates of Reaction (page 142) Flashcards
What is meant by ‘The rate of a Chemical Reaction’?
It is how fast the reactant are changed into products
(rates of reacton are pretty important. In the chemical industry, the faster you make chemicals, the faster you make money)!
What is one of the slowest chemical reactions?
one of the slowest is the rusting of Iron
Apart from Iron, what other slow reaction include chemical weathering?
Acid rain damage to limestone buildings
What is an example of a moderate speed reaction?
This would be the metal magnesium reacting with an acid to produce a gentle steam of bubbles.
What would be a fast chemical reaction?
Burning is a fast reaction, but explosions are even faster and release a lot of gas. Explosive reactions are all over in a fraction of a second.
What do you need to understand for the ‘Rate of Reaction’?
Graphs need to be understood
How can you find the speed of a reaction?
you can find this by recording the amount of product formed, or the amount of reactant used up over time (see page 144)
When you look at a graph (see diagram on page 142), what do the graph tell you?
The steeper the line on the graph, the faster the rate of reaction. Over time the line becomes less steep as the reactants are used up.
See graph on page 142, and explain what the graph shows for the quickest reactions?
the quickest reactions have the speepest lines and become flat in the least time.
Graph 1 represents the original reaction
Graphs 2 and 3 represent the reaction taking place quicker, but with the same initial amounts of reactants. The slopes of the graphs are steeper than for graph 1.
Graphs 1, 2, and 3 all converge at the same level, showing that they all produce the same amount of product although they take different times to produce it.
Graph 4 shows more product and a faster reaction. This can only happen if more reactant(s) are added at the start.
What is ‘Collision Theroy’?
Collision Theroy is the rate of a chemical reaction.
- The collision frequency of reacting particles (how often they colide). 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 successful.
As explained on page 139, that the minimum amount of energy that particles need to react is called the ‘Activation Energy. Particles need this much energy to break the bonds in the reactants and start the reaction.
Factors that increase the number of collisions (so that a greater proportion of reaching particles colide), or the amount of energy particles collide with will increase the rate of the reaction
Collision theory’s essential for understanding how different factors affect the rate of reaction - so make sure you understand it before moving on to the rest of Topic C6
What is meant by the term activation energy? (1 mark)
The activation energy for a reaction is the minimum amount of energy that particles need to react (1 mark)
