% Comp, Isotopes, Hydrates

percentage composition: the relative mass of each elemt in a compound

mass of element/total mass x 100 = percent comp.

Isotopes:

isotopes are atom of an element that have the same number of protons but different numbers of neutrons

they have chemical properties that are essentially identical, but differ in masses

AAM = (m1)(a1) + (m2)(a2)

Don’t forget to divide the abundances by 100, to get the proper percentage. The answer is the average between the two atomic masses.

When you are given the average atomic mass, two masses but are missing the abundences:

AAM = (m1)(x) + (m2)(1-x)

Hydrates:

ionic compounds (salts) that have a definite amount of H2O as part of their structure

Formula:

anhydrous salt • nH2O …. CaSO4 • H2O Calcium sulfate dihydrate

When you have to find n, you find the number of moles in the AS and H2O and then divide.