Chemistry 7

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  • Created by: Adele
  • Created on: 08-06-13 11:24

Rates of Reaction

The rate of reaction depends of four things:

1. Temperature 

2. Concentration (or pressure)

3. Catalyst 

4. Size of particles 

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Measuring Rates of Reaction

Rate of Reaction= amount of reactant used or amount of product formed 


Ways of measuring speed of reaction:

1. Precipitation (precipitate clouds solution) 

The quicker the marker disappears, the quicker the reaction.

2. Change in mass (usually gas given off)

The quicker the reading on the balance drops, the faster the reaction.

3. The volume of gas given off

The more gas given off during a given time interval, the faster the reaction.

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Collision Theory

The rate of reaction depends on how often or how hard reacting particles collide with each other. the idea is that particles have to collide to react but also they have to collide hard enough (with sufficient energy). 

More collisions increases the rate of reaction. Higher temperature,higher concentration, larger surface area and catalysts cause an increase in rate of reaction. 

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A catalyst changes the speed of a reaction, without changing or being used up in the reaction.

A catalyst lowers activation energy therefore causing reactions to react at a lower temperature.

A catalyst works best when they have a big surface area this large surface area enables particles to react quickly.

Catalysts can help reduce costs in reactions within industry. 

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Energy Transfer

Exothermic reactions give out energy to the surroundings (generally in form of heat)

Forms of exothermic reactions are: 

1. Burning fuels

2. Neutralisation reactions

3. Oxidation reactions

Endothermic reactions take energy in from surroundings

An example of this type of reaction is thermal decomposition 

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Reversible Reactions

A reversible reaction is one where the products of the reaction can themselves react to produce the original reactants. 

Reversible reactions will reach dynamic equilibrium (reactions are still taking place in both directions), the reactions taking place are the same rate in both directions. 

In a reversible reaction the position of equilibrium (amounts of reactants and products) depends on temperature and pressure surround the reaction. 

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The Haber Process

Industrial process producing ammonia, which is used to make fertilisers. 

The reaction is reversible, and the iron catalyst used speeds up the reactions and keeps costs for the process down. 

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Electrolysis is breaking down a substance using electicity. It requires a liquid to conduct the electricity this is called electrolyte. Electrolytes are usually free ions dissolved in water. 

In electrolysis it needs a complete circuit therefore needs a flow of electrons.

Electrolysis is used in purifying substances such as copper.

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Cost of Pharmaceutical Drugs

Pharmaceutical drug costs differ because of many factors such as: 

1. Market research- identifying new drug so that there is not competition and so that it is in demand.

2. Research and Development- finding suitable compounds, testing and modifying the compound.

3. Trialling- testing including animal and human trials

4. Marketing- advertising 

5. Manufacture- batch production 

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