Transcription of Tutorial 2 FORMULAS, PERCENTAGE COMPOSITION, AND …
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T-6 Tutorial 2 FORMULAS, PERCENTAGE COMPOSITION, AND THE MOLEFORMULAS: A chemical formula shows the elemental composition of a substance: thechemical symbols show what elements are present and the numerical subscripts show howmany atoms of each element there are in a formula unit. Examples:NaCl: one sodium atom, one chlorine atom in a formula unitCaCl2: one calcium atom, two chlorine atoms in a formula unitMg3N2: three magnesium atoms, two nitrogen atoms in a formula unitThe presence of a metal in a chemical formula indicates an ionic compound, which is composedof positive ions (cations) and negative ions (anions). A formula with only nonmetals indicates amolecular compound (unless it is an ammonium, NH4+, compound). Only ionic compounds areconsidered in this are tables of common ions in your lecture text, p 56 (cations) and p 57 (anions).
We now have two sets of numbers which show mass relationships among the elements in sodium sulfate: (1) the formula mass and (2) the percentage composition. From the formula mass on page T-9 various mass ratios, that is, conversion factors, may be obtained: 45.98 g Na 142.04 lbs Na 2SO 4 32.06 g S
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