# MOLE CALCULATIONS REVISION

THIS IS A SUMMARY TO THE MOLE CALCULATIONS,ALMOST ALL MOLE CALCULATIONS...THESE HELPED ME ALOT,,HOPE THEY HELP U TOO..

- Created by: Shah
- Created on: 05-05-13 15:19

First 220 words of the document:

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 gas) = volume in cm³/24000cm³

Empirical Formula

Gives you the moles of each atom and the ratio of moles

1. Divide given percentage/mass by r.a.m

2. Divide each answer by the smallest answer

3. If ratios are not whole numbers, multiply each answer by a small integer

Example:

A compound contains 39.13% carbon, 52.17% oxygen and 8.70% hydrogen. Calculate

the empirical formula.

Step 1 (divide by r.a.m)

Carbon: 39.13/12 = 3.26

Oxygen: 52.17/16 = 3.25

Hydrogen: 8.70/1 = 8.70

Step 2 (divide by smallest)

Carbon: 3.26/3.25 = 1

Oxygen: 3.25/3.25 = 1

Hydrogen: 8.70/3.26 = 2.66

Step 3 (multiply all by small integer)

Carbon: 1 x 3 = 3

Oxygen: 1 x 3 = 3

Hydrogen: 2.66 x 3 = 8

.:. Empirical formula is C3H8O3

Molecular Formula

To find the molecular formula we need to use the molecular formula mass and the

empirical formula mass.

Molecular formula mass = empirical formula mass x an integer

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