Chapter 2 - 1 Sample Significant Figure Problem A sample of...

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Unformatted text preview: 1 Sample Significant Figure Problem A sample of sodium chloride is weighed by difference on a balance. The masses are: Sample + Bottle: 20.21 g Bottle: 19.65 g Enough water is added to the bottle to bring the total mass to 25.00 g. What is the percent of sodium chloride in the final solution by weight, expressed with the correct number of significant figures? A) 0.1047 % B) 10.47 % C) 10.5 % D) 10. % or (1.0 x 10) % 2 2 Chemical Formulas and Composition Stoichiometry 3 Chapter Goals 1. Chemical Formulas 2. Ions and Ionic Compounds 3. Names and Formulas of Some Ionic Compounds 4. Atomic Weights 5. The Mole 4 Chapter Goals 1. Formula Weights, Molecular Weights, and Moles 2. Percent Composition and Formulas of Compounds 3. Derivation of Formulas from Elemental Composition 4. Determination of Molecular Formulas 5. Some Other Interpretations of Chemical Formulas 6. Purity of Samples 5 Chemical Formulas Chemical formula shows the chemical composition of the substance. ratio of the elements present in the molecule or compound He, Au, Na monatomic elements O 2 , H 2 , Cl 2 diatomic elements O 3 , S 8 , P 4- more complex elements H 2 O, C 12 H 22 O 11 compounds Substance consists of two or more elements 6 Chemical Formulas Compound 1 Molecule Contains HCl 1 H atom & 1 Cl atom H 2 O 2 H atoms & 1 O atom NH 3 1 N atom & 3 H atoms C 3 H 8 3 C atoms & 8 H atoms 7 Ions and Ionic Compounds Ions are atoms or groups of atoms that possess an electric charge. Two basic types of ions: Positive ions or cations one or more electrons less than neutral Na + , Ca 2+ , Al 3+ NH 4 +- polyatomic cation Negative ions or anions one or more electrons more than neutral F- , O 2- , N 3- SO 4 2- , PO 4 3-- polyatomic anions 8 Ions and Ionic Compounds Sodium chloride table salt is an ionic compound 9 Names and Formulas of Some Ionic Compounds Table 2-1 gives names of several molecular compounds. You must know all of the molecular compounds from Table 2-1. Some examples are: H 2 SO 4- sulfuric acid H2O - water C 2 H 5 OH - ethanol 10 Names and Formulas of Some Ionic Compounds Table 2-2 displays the formulas, charges, and names of some common ions You must know the names, formulas, and charges of the common ions in table 2-2. Some examples are: Anions - Cl 1- , OH 1- , SO 4 2- , PO 4 3- Cations - Na 1+ , NH 4 1+ , Ca 2+ , Al 3+ 11 Names and Formulas of Some Ionic Compounds Formulas of ionic compounds are determined by the charges of the ions. Charge on the cations must equal the charge on the anions. The compound must be neutral. NaCl sodium chloride (Na 1+ & Cl 1- ) KOH potassium hydroxide(K 1+ & OH 1- ) CaSO 4 calcium sulfate (Ca 2+ & SO 4 2- ) Al(OH) 3 aluminum hydroxide (Al 3+ & 3 OH 1- ) 12 Names and Formulas of Some Ionic Compounds You do it!...
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This note was uploaded on 04/16/2011 for the course CHEM 1211 taught by Professor Atwood during the Spring '07 term at University of Georgia Athens.

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Chapter 2 - 1 Sample Significant Figure Problem A sample of...

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