# Relative Formula Mass

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- Created by: Brooke
- Created on: 15-07-13 13:39

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- Relative Formula Mass (RFM)
- Calculating RFM
- To calculate the RFM, all you have to do is add up the RAM of of all the atoms present in the formula
- Most candidates do not have a problem calculating RFM until they meet an example involving water of crystallisation

- Most candidates do not have a problem calculating RFM until they meet an example involving water of crystallisation

- To calculate the RFM, all you have to do is add up the RAM of of all the atoms present in the formula
- The Mole
- The mole is a measure of the AMOUNT OF SUBSTANCE
- One mole (1 mol) is the amount of substance that contains 6x10 to the 23 particles (atoms, molecules or formulae) of the substance
- 6x10 to the 23 is known as AVOGADRO NUMBER
- For example, 1 mol of Sodium (Na) contains 6x10 to the 23 ATOMS of sodium

- Calculating the mass of one mole
- The mass of one mole of atoms is easily calculated. It is simply RAM expressed in grams
- The mass of one mole is also easily calculated by working out the formula mass and expressing it in grams

- The mass of one mole is also easily calculated by working out the formula mass and expressing it in grams

- The mass of one mole of atoms is easily calculated. It is simply RAM expressed in grams

- Simple Calculations with moles
- 1. CALCULATING MASS FROM NO. OF MOLES
- Mass of substance (in grams) = amount of moles x RFM

- Mass of substance (in grams) = amount of moles x RFM
- 2. CALCULATING AMOUNT FROM MASS
- Amount in moles = mass/RFM

- Amount in moles = mass/RFM
- 3.CALCULATIONS WITH ATOMS OF ELEMENTS
- These types of calculations are important when working out the empirical formula of compounds

- 1. CALCULATING MASS FROM NO. OF MOLES
- Molar volume of a gas
- One mole of any gas has a volume of 24dm cubed (24000cm cubed) at room temp. This is called the molar volume of a gas
- 1. CALCULATING VOLUME OF GAS FROM AMOUNT OF GAS
- 2. CALCULATING AMOUNT OF GAS FROM THE VOLUME OF GAS

- Calculating RFM

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