1 - Ar, Mr, The Avogadro’s constant and Moles

Concentration of a solution

refers to the amount of solute that is dissolved per unit volume of solution. It is a way to express how much solute is present in a given amount of solution.

What are the two ways that concentration is measured

g dm^-3 or mol dm⁻³. This is grams per decimetre cubed or moles per decimetre cubed

What is the equation linking mass, volume and concentration?

Relative Atomic Mass (Ar)

The average mass of an atom of an element, compared to a 1/12th of the mass of a Carbon-12 atom

Relative Molecular Mass (Mr)

The average mass of a molecule of a compound, compared to a 1/12th of the mass of a Carbon-12 atom

Relative formula mass (M_r)

The average mass of a formula unit compared to 1/12^th of the mass of an atom of carbon-12.

RFM is used for ionic and giant covalent substances.

Calculating Ar, given isotopes and abundances

/$\frac{\left(\left(IsotopeA\cdot AbundanceA\right)+\left(IsotopeB\cdot AbundanceB\right)\right)}{AbundanceA+AbundanceB}$

Calculating Ar given Mass spectrometer

$$\frac{\left(\left(Abundance\ A\ \times\ m/z\ A\ \right)\ +\left(Abundance\ B\ \times\ m/z\ B\right)\right)}{Total\ Relative\ abundance}$$