# Science P3 C3 B3

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• Created by: Zoe
• Created on: 21-02-14 13:37

Things that affect rate of reaction:

·         Catalyst

o   Increases the rate of reaction.

·         Temperature

o   Temperature increase means a rate of reaction increase.

·         Concentration

o   The higher concentrate a solution the more solute that is dissolves in the solvent, particles become closer so have more chance of successful collisions.

·         Pressure

o   Pressure increases so does rate of reaction, particles become more crowded so have more successful collisions.

·         Surface area

o   Rate of reaction increases if a powder is uses because there is a bigger surface area so more particles are exposed so ready to collide.

Equation:

Amount of reactant used or amount formed

Time taken

Every element has two numbers the top number is the relative atomic mass for that elements atoms. The relative formula mass or Mr of a substance is the mass of a unit of that substance compared to the mass of a carbon atom. To find the Mr you add the Ar values of the atoms in the formula.

Mr – relative formula mass

Ar – Atoms

You don’t always get 100% yield from a reaction. Product is often lost during handling and purification. Some cant get lost during filteration as some gets caught in the filter paper. Some liquids evaporate. Some liquid can get spilled or left in containers.

To work out the percentage yield:

x 100

Actually yield

Percentage yield

Calculating theoretical mass:

x Mr of products

Mass of reactants

Mr of reactants

Exothermic – gives energy out to its surroundings

Endothermic – takes energy in to itself in to its surroundings

Whether a reaction is exothermic or endothermic is determined by the difference between the energy needed to break the bonds and the energy that is given out when bonds form.

4 types of energy that can be given out are:

1.       Heat

2.       Light

3.       Sound

4.       Electrical

The temperature increases when an acid is added to an alkali. An example of an exothermic reaction are fireworks. An example of an endothermic reaction is electrolysis.

A product made in a continuous process is made all the time. Bulk chemicals are needed all the time. Batch process is not made all the time. Specialist chemicals are more expensive than bulk because there are less of them made and are produced in small amounts.

The Haber process conditions are a compromise between maximising the yield and keeping costs reasonable. Key features of the Haber process is high pressure, temperature at 405 degrees Celsius,  unreacted gases are recycles and they use an iron catalyst.

This is the process when developing a new drug:

·         Thousands of substances are tested to see if they are useful through a computer simulation. Compounds are indentified which may have a beneficial effect on a disease. They then make compounds from raw materials.

·         The most promising substance are tested on laboratory animals.

·         They