# C6- the rate and extent of chemical changes

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• Created by: chlo chlo
• Created on: 02-03-19 17:04

## rates of reaction

How fast the reactants are changed into products.

The steeper the line of the graph, the faster the reaction.

The quickest reactions are the ones that go up the quickest then becomes flat in the least amount of time.

Reaction rate is explained by the collision theory:

• The collision frequency- how often particles collide
• Energy transferred during a collision

The minimum amount of energy needed to start a reaction is called the activation energy.

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## factors affecting rate of reaction

increasing temperature:

• particles move faster meaning collide more frequently
• more collisions will occur

concerntartion or pressure:

• more particles in the same volume
• collisions are more frequent

increasing surface area:

• increase surface area to volume ratio
• more area for reactions to occur

using a catalyst:

• speeds up reaction without being used up
• decreases activation energy
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## measuring rate of reaction

1) precipitation

• if initail solution is transparent then turns cloudy, the product is a precipitate
• measure how long it takes for a mark to disappear. thefaster the mark disappers the quicker the reaction
• results are very subjective- different people may see the change at a different point

2) change in mass

• as gas is released the mass will 'disappear'
• quicker the reading drops the quicker the reaction

3) volume of gas given off

• using a gas syringe to measure the amount of gas given off
• more gas given off in an interval the faster the reaction
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## Le Chatelier's Principle

The idea that if you change the conditions of a reversible reaction, it'll try and counteract the change

temperature:

• all reactions are exothermic one way and endothermic the other
• if you decrease the temp. equilibrium will move in the exothermic direction and vice versa

pressure:

• only affects reactions involving gases
• increasing pressure , moves in direction of fewer molecules and vice versa

concerntration:

• changing conc. of either reactants or products the system will not be at equilibrium
• increase conc of reactants then makes more products
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