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Mole Calculations Cheat Sheet by

Conven­tions and Rules

* Molar mass is the mass of one mole of atoms in a substance.
* 1 mole of any gas is 24dm3 at r.t.p.
* Avogadro's Constant is the number of particles in one mole of any substance. The number is 6 x 1023.
* Relative Atomic Mass is the mass of one atom of an element compared to 1/12 of the mass of one carbon-12 atom.
* Relative Molecular Mass is the mass of one molecule of an element compared to 1/12 of the mass of one carbon-12 atom.
* Relative Formula Mass is the mass of one formula unit of an ionic compound. It is the sum of the Ar of all the ions in the formula unit.
* 1000cm3 = 1 dm3

Formula Triangles

Top
Bottom 1
Bottom 2
No. of Particles
No. of Moles
Avogadro's No.
Mass in Grams
No. of Moles
Molar Mass in g/mol
Volume of Gas in dm3
No. of Moles
24dm3
Mass in g
Volume in dm3
Mass Concen­tration in g/dm3
No. of Moles
Volume in dm3
Molar Concen­tration in mol/dm3
* To find top, multiply bottom values. To find bottom, take top divided by other bottom value.

1. No. of Particles // Moles // Avogadro's No.
2. Mass // Moles // Molar Mass
3. Volume // Moles // 24dm3
4. Mass // Volume // Mass Concen­tration
5. Moles // Volume // Molar Concen­tration

Concen­tration

* The amount of solute dissolved in a unit volume of the solution.
* Usually in g/dm3 or mol/dm3.
* Mol/dm3 is also called Molarity.
* 1M = 1 mol/dm3
 

Molecular Formula & Empirical Formula

Value
Element A
Element B
Mass in Grams
x
x
Molar Mass
x
x
Moles
x
x
Mole Ratio
x
x
1. Given % Compos­ition, find masses of both substances in 100g. If 70% is A and 30% is B, then there is 70g of A and 30g of B in 100g of AB.
2. Find molar mass using periodic table.
3. Find no. of moles by multip­lying mass and molar mass.
4. Divide all sides by the smallest number and round off to the nearest whole number to get mole ratio.
5. Molecular Formula is always a multiple of the Empirical Formula.

% Purity and % Yield

% Purity = Mass of Pure Substance / Total Mass x 100%

% Yield = Actual Mass / Theore­tical Mass x 100%

Limiting Reagents & Reactants in Excess

x
No. of Available Moles
vs
No. of Moles Needed
Limiting Reagents
No. of Available Moles
<
No. of Moles Needed
Reactants in Excess
No. of Available Moles
>
No. of Moles Needed
 

How to Find Limiting Reagents

A + 2B 2AB

1. Find no. of available moles for A.
2. Find no. of available moles for B.
3. Find no. of moles needed for A/B.
E.g. Moles needed for A = Available moles for B / 2
(Refer to mole ratio)

If moles available is < moles needed, then that reactant is the limiting reagent.
The concept of limiting reagents is the available moles for reaction vs the needed moles for reaction.

Mole Calcul­ations

Given
  
Find
Mass of A
Moles of A
Moles of B
Mass of B
Vol. of A
Moles of A
Moles of B
Vol. of B
Mass of A
Moles of A
Moles of B
Vol. of B
Vol. of A
Moles of A
Moles of B
Mass of B
Refer to mole ratio when converting Moles of A to Moles of B.
1 mole of any gas is 24dm3 at R.T.P.

Acids & Bases

Metal + Acid Salt + Hydrogen Gas
Metal Carbonate + Acid Salt + Water + Carbon Dioxide
Metal Oxide + Acid Salt + Water
Metal Hydroxide + Acid Salt + Water
Base + Acid Salt + Water (Neutr­ali­sation)
Alkali + Acid Salt + Water
Alkali + Ammonium Salt Salt + Water + Ammonia Gas
Alkali + Salt Metal Hydroxide + Salt
       
 

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