Rate of reaction

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How to find the rate of reaction

Rate of reaction can be found in different ways:

1. Measuring the amount of reactants used

-If one of the products is a gas, measure the mass (in grams) of the reaction mixture before and after the reaction takes place and the time it takes for the reaction to happen.

-The mass of the mixture will decrease

-As the reaction takes place the reactant is used up, so the amount of reactant remaining decreases

-The concentration of the reactant is calculated as the amount divided by the volume of the reaction mixture

2. Measuring the amount of products formed

-If one of the products is a gas, measure the total volume of gas produced in cubic centimetres with a gas syringe and the time it takes for the reaction to happen

3. Measuring the time it takes for a reaction mixture to become opaque or change colour

-Time how long it takes for the mixture to change colour

-Rate of reaction = 1 ./. time taken for solution to change colour

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Collision Theory

Chemical reaction only occur when reacting particles collide with each other with sufficient energy.

The minimum amount of energy required to cause a reaction is called the activation energy

There are 4 important factors that affect the rate of reaction: temperature, concentration, surface area and catalysts:

Temperature

-In a hot reaction mixture the particles move more quickly - they collide more often and with greater energy, so more collisions are successful

Concentration

-At higher concentrations, the particles are crowded closer together - they collide more often, so there are more successful collisions

-Increasing the pressure of reacting gases also increases the frequency of collisions.

Surface Area

-Small pieces of a solid reactant have a large surface area in relation to their volume

-More particles are exposed and available for collisions, so there are more collisions and a faster reaction.

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Plotting Reaction Rates

Graphs can be plotted to show the progress of a chemical reaction. There are three key things to remember:

-The steeper the line, the faster the reaction

-When one of the reactants is used up, the reaction stops (horizontal line)

-The same amount of product is formed from the same amount of reactants, regardless of rate

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Plotting Reaction Rates

Graphs can be plotted to show the progress of a chemical reaction. There are three key things to remember:

-The steeper the line, the faster the reaction

-When one of the reactants is used up, the reaction stops (horizontal line)

-The same amount of product is formed from the same amount of reactants, regardless of rate

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