Key Concepts: Moles

The mole is a fundamental unit in chemistry, representing 6.02 x 10^23 particles (atoms, molecules, ions, electrons, etc.). This number is also known as Avogadro’s number.
Particles are counted in moles because they’re too small to count individually. Thinking in terms of moles makes calculations more feasible.
The mass of one mole (known as molar mass) of any substance (element or compound) can be calculated. This is numerically equal to the relative atomic/molecular mass of the element/compound but the unit is grams (g).
To find the number of moles of a substance, divide the mass of the substance by its molar mass.
Molar calculations are essential in chemical equations, which show the ratio of moles involved in a chemical reaction. This concept allows predicting the amount of product that will form or the amount of reactants needed.
It’s possible to convert volume into moles for gases at room temperature and pressure using the fact that one mole of any gas occupies 24dm^3 (24,000 cm^3). This is known as the molar volume.
Solution concentrations are often given in mol/dm^3. To calculate the concentration, you divide the number of moles of solute by the volume of the solvent (in dm^3).
Volume of a gas, mass of a solid, or concentration of a solution can be useful in determining the ‘limiting reactant’ in a reaction i.e., the reactant that runs out first, limiting further reaction.
When using moles, be mindful of ‘per’ notations: grams per mole (g/mol), moles per litre (mol/L), etc. It’s crucial to keep track of these to prevent confusion and errors in calculations.
Amount of substance present doesn’t affect the amount of energy transferred in a reaction. It isn’t about having more or less substance, but about how vigorous the reaction is at a molecular level.
Understanding moles is key in topics like stoichiometry, yielding reactions, and energy changes. It’s a central part of the foundations of chemistry, and needed for more complex topics.