{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

composition+stoichiometry+part+01

# composition+stoichiometry+part+01 - Principles of General...

This preview shows pages 1–3. Sign up to view the full content.

1 Composition Stoichiometry Principles of General Chemistry, 2 nd ed. By M. Silberberg Chemistry, 8th ed. by W. Whitten, R. Davis, R., M. L. Peck, and G. Stanley. 2 Lecture The Mole Atomic Weights Formula Weights, Molecular Weights and Moles Percent Composition Derivation of Formulas from Elemental Composition Determination of Molecular Formulas Some Other Interpretations of Chemical Formulas Purity of Samples The Atomic Weights If we define the mass of 12 C as exactly 12 atomic mass units (amu), then it is possible to establish a relative weight scale for atoms. 1 amu = (1/12) mass of 12 C by definition 3 Atomic Weight - weighted average of the masses of the constituent isotopes of an element. Example. Naturally occurring Cu consists of 2 isotopes. It is 69.1% 63 Cu with a mass of 62.9 amu, and 30.9% 65 Cu, which has a mass of 64.9 amu. Calculate the atomic weight of Cu to one decimal place. 4 The Atomic Weights Example. The atomic weight of boron is 10.811 amu. The masses of the two naturally occurring isotopes 5 10 B and 5 11 B, are 10.013 and 11.009 amu, respectively. Calculate the fraction and percentage of each isotope. 5 The Atomic Weights 6 The Mole A number of atoms, ions, or molecules that is large enough to see and handle. A mole = number of things Just like a dozen = 12 things One mole = 6.022 x 10 23 things Avogadro’s number = 6.022 x 10 23 Symbol for Avogadro’s number is N. One mole (1 mol) contains 6.022 x 10 23 entities (to four significant figures)

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
7 Interconverting Moles, Mass, and Number of Chemical Entities Mass (g) = no. of moles x no. of grams 1 mol No. of moles = mass (g) x no. of grams 1 mol No. of entities = no. of moles x 6.022 x 10 23 entities 1 mol No. of moles = no. of entities x 6.022 x 10 23 entities 1 mol g No. of moles = mass (g) x no. of grams 1 mol mol 8 Example: Calculate the mass of a single Mg atom in grams to 3 significant figures.
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 5

composition+stoichiometry+part+01 - Principles of General...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online