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Chemistry: Calculations Part I

This will cover:

Measurements

Calculations Example

Moles

Measurements:

Mole = Mass of an element (g) / Mass Number of the element (Ar)

Mass = Moles X Ar

For example:

The mass of 0.1 moles of carbon atoms

(Moles) X 12 (mass no.) = 1.2 (mass)

Calculations Example:

If C = 12 and O = 16

Carbon + Oxygen = Carbon Dioxide

C + O2 = CO2

12 + 2x16 = 12 + (2x16)

12g + 32g = 44g

Therefore we need 32g of oxygen to react 12g of carbon and 44g of carbon dioxide is produced.

Moles:

1M means that 1 mole of a substance dissolved in 1000 cm3 of its solution. In 100 cm3 of a 2M solution there are 0.2 moles. This is because they are 2M for every 1000cm3 solution. If it had been a 3M solution, the number of moles in 100cm3 would have been 0.3 etc.

The equation for this is:

Number of Moles in a solution = Molarity x (volume of solution cm3 / 1000)

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