Chemistry 1027A/B Chapter Notes -Chemical Formula, Molar Mass, Sodium Chloride

• School: Western University
• Department: Chemistry
• Course: Chemistry 1027A/B
• Professor: Felix Lee

Document Summary

Isotope elements with the same number of protons, but different number of neutrons, therefore they have different mass numbers. Average atomic mass = (percent of isotopic abundance/100. Average atomic mass = (92. 23/100 x 28) + (4. 67/100 x 29) + (3. 10/100 x 30) = 28. 1u. Cation an atom that loses one or more electrons and becomes positively charged. Anions an atom that gains one or more electrons and becomes negatively charged. Avagadro"s number - # of atoms/molecules in one mole of a substance = 6. 02x1023mol-1. Example: convert 1. 85mol of c6h12o6 to atoms. (1. 85mol)( 6. 02x1023molecules/mole) = 1. 11x1024 molecules of c6h12o6 (1. 11x1024 molecules)(6 + 12 + 6 atoms) = 2. 67 x1025 atoms in c6h12o6 n (number of moles) = mass (g)/molar mass (gmol-1) Example: find the number of moles in 12. 29g of h2o nh2o = 12. 92g/18. 02gmol-1 = 0. 72mol h2o. Mass percent percent of mass of one species in relation to the mass of the entire molecule.