counting particles by mass: the mole

relative molar mass

the ratio of a molecule to one twelfth of the mass of a carbon-12 atom

- ratio so no units

hydrates

compounds in which water molecules form coordination bonds with ions

mole, mass equation

n=m/M

empirical formula

shows the simplest ratio of atoms of the different elements that are present in the substance

- shows the mole ratio of elements in a compound

- ions empirical formula is also known as a formula unit

molecular formula

shows the actual number of atoms of each element in the molecule of that substance

- integer multiple of the empirical formula

dilutions

when you dilute, you add a solvent

the moles of solute stay the same, but the volume increases, so the concentration decreases

volume and concentration are inversely related

spectrophotometry

an analytical technique based on the measurement of the intensity of visible, ultraviolet and near-infrared radiation

colorimetry

same principles as spectrophotometry but limited to visible light

avogadro's law

equal volumes of any two gases at the same temperature and pressure contain equal numbers of molecules

- volume is directly proportional to moles