Composition of Substances and Solutions

Formula mass

sum of the atomic masses of the atoms in the chemical formula

One mole

the amount of substance that contains as many atoms, molecules, or other objects, as the number of atoms in 12 grams of isotopically-pure 12C

avogadro's number

6.022 x 10^23

Percentage composition

percentage, by mass, contributed by each element

Empirical formulas:

give relative number of atoms of each element in a substance

Molecular formulas

give actual number of atoms in a substance

Solution:

a homogeneous mixture of two or more substances

Solvent:

the substance present in greatest quantity

Solutes:

dissolved in the solvent

Molarity (M) =

(moles of solute) / (volume of solution in liters)

ppm =

mass of solute/mass of solution x 10^6

ppb =

mass of solute/mass of solution x 10^9

1 ppm =

1000 ppb