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Chemistry: Topic 1.1 Calculations

Calculating No. of Moles:
There are 3 ways to calculate the number of moles (depending on the information given):

1. Moles (of a substance) = given mass in grams/Ar or Mr
2. Moles (in a solution) = concentration x (volume in cm³/1000)
3. Moles (of a…

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Example:
A hydrocarbon with Relative Molecular Mass (Mr) of 28gmol-1 has the following
composition: carbon 85.7% and hydrogen 14.3%. Calculate the hydrocarbon's molecular
formula.

Step 1 (find empirical formula mass)
Carbon: 85.7/12 = 7
Hydrogen: 14.3/1 = 14.3

Carbon: 7/7 = 1
Hydrogen: 14.3/7 = 2

.:. Empirical formula =…

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Example:
What is the volume of 5.6 x 10-2 moles of chlorine molecules?

Volume = 0.0056 x 24000 = 134.4cm³

Example:
Calculate the volume of 10g of hydrogen gas.

Moles = 10/2 = 5 moles
Volume = 5 x 24000 = 120000cm³ = 120dm³

Example:
Calculate the mass of 1000cm³…

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