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The Mole - Chemistry (Formula Sheet)

The document discusses key concepts for relating moles, volume, mass, and concentration of gases. It provides formulas for calculating volume from moles and molar volume, moles from mass and molar mass, limiting reactants, and converting between units of concentration. Empirical and molecular formulas can be determined from elemental composition. Percentage yield compares actual to theoretical yield, while percentage purity compares pure substance mass to total sample mass.

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Ali Usman Abdullah
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9K views4 pages

The Mole - Chemistry (Formula Sheet)

The document discusses key concepts for relating moles, volume, mass, and concentration of gases. It provides formulas for calculating volume from moles and molar volume, moles from mass and molar mass, limiting reactants, and converting between units of concentration. Empirical and molecular formulas can be determined from elemental composition. Percentage yield compares actual to theoretical yield, while percentage purity compares pure substance mass to total sample mass.

Uploaded by

Ali Usman Abdullah
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
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The Mole & the Volume of Gases

Formula triangle showing the relationship betwe- Formula triangle showing the relationship

en moles of gas, volume in dm3 and the molar volume between moles of gas, volume in cm3 and the

molar volume

 To find the volume of a gas : Volume = Moles x Molar Volume


 To find the moles of a gas: Moles = Volume ÷ Molar Volume

Linking Moles, Mass and RFM

Formula triangle for moles, mass and molar mass

TO CALCULATE MOLES : MASS/ MOLAR MASS

TO CALCULATE MASS : MOLES X MOLAR MASS

To find number of particles/entities in a substance: moles X 6 X 1023


Reacting Masses
To find a limiting reactant:

1. Write the balanced equation for the reaction


2. Calculate the moles of each reactant
3. Compare the moles & deduce the limiting reactant

Calculating Concentration
To calculate concentration in g/dm3

To calculate concentration in mol/dm3

To go from cm3 to dm3 :

 Divide by 1000

To go from dm3 to cm3 :

 Multiply by 1000

To go from g dm-3 to mol dm-3 :

 Divide by the molar mass in grams

To go from mol dm-3 to g dm-3:

 Multiply by the molar mass in grams


Empirical & Molecular Formula
To calculate empirical formula:

A compound contains 10 g of hydrogen and 80 g of oxygen. What is its empirical formula of


this compound?

hydrogen oxygen
Write the mass of each element 10 80
Divide each mass by the relative atomic
10/ 1= 10 80/ 16= 5
mass
Find the ratio by dividing by the smallest
10/5 = 2 5/5= 1
number
Empirical formula = H2O

To calculate molecular formula:

Relative formula mass of molecular formula/ relative formula mass of empirical formula

Percentage Yield & Purity


Why no 100% yield?

 Some reactants may be left behind in the equipment


 The reaction may be reversible and in these reactions a high yield is never possible
as the products are continually turning back into the reactants
 Some products may also be lost during separation and purification stages such as
filtration or distillation
 There may be side reactions occurring where a substance reacts with a gas in the
air or an impurity in one of the reactants
 Products can also be lost during transfer from one container to another

Percentage yield

It compares the actual yield to the theoretical yield

Percentage Purity

% purity= mass of pure substance X 100 / total mass of substance

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