Unit 1: topic 1: formula, equations and amount of substances

FORMULA, EQUATIONS AND AMOUNT OF SUBSTANCES

Atomic Number - protons

Mass Number - protons + neutrons

Relative Atomic Mass (RAM) - average mass of atoms of an element relative to 1/12 mass of a carbon-12 atom.

Relative Isotopic Mass (RIM) - mass of an atom of an isotope relative to 1/12 mass of a carbon-12 atom.

Element - substance with atoms with the same atomic number.

Ion – bonded atoms that have lost/gained electrons.

Loss= more protons, + charge.

Gain= more electons, - charge.

Molecule – atoms (2 or more) covalently bonded.

Compound- substance containing atoms bonded .

If covalent the compound is made up of molecules. If ionic the formula is in the simplest ratio.

Amount of substance and the Avogadro constant

Amount = number of moles

Mole – amount of substance (number of moles of substance) containing same number of particles as 12g of carbon-12 atoms. Particles = molecules, ions, atoms etc.

Avogadro Constant – 6.02 x 1023

Molar Mass – Mass in grams. (same as relative molecular mass but in grams)

Concentration

-       Concentration is the amount of solute dissolved per dm3 of solution.

-       Concentration (g dm-3) = Mass (g) / Volume (dm3)

-       Mol dm-3

-       Concentration = Moles / Volume (dm3 )

-       You can calculate the mass with a known volume and known concentration:

-       Find mole (amount) of substance = concentration x volume

-       Find mass of substance = mol x molar mass

-       (Sometimes volume is given in cm3 so divide by 1000 to make dm-3)

PPM (parts per million) or parts of solute per million parts of solvent  is The ratio of one gas to another.

-       1ppm is 10 -6 g ( microgram) 

-       For mass/volume concentrations: 1 ppm = 1 g m-3 = 1 mg L-1 = 1 μg cm-3

-      …