CHEM 101 Chapter Notes - Chapter 3: Molar Mass, Chemical Formula, Unified Atomic Mass Unit
Document Summary
Decomposition reactions: a single reactant breaks apart to form two or more substances, many compounds react this way when heated (metal carbonates decompose to form metal oxides and carbon dioxide when heated) Molecular weight: mw: sum of the atomic weights of the atoms in a molecule, generally reported for molecular compounds, chemical formula = that of a molecule fw = mw (molecular weight) Percentage composition from chemical formulas: elemental composition: calculating the percentage composition of any element in a substance mass composition of element= (cid:4666)number of atoms of element(cid:4667)(cid:4666)atomic weight of element(cid:4667) formula weight of substance. Avogadro"s number and the mole: one mole is avogadro"s number (6. 02 1023) of objects one mole of atoms is 6. 02 1023 atoms. Interconverting masses and numbers of particles: example: calculating the number of copper atoms in an old copper penny, penny has a mass of about 3 g, and we will assume it is 100% copper.
