Chemical Names and Formulas Chapter 7

Chemical Formulas Chemical Formulas – number of each kind of atom Ex. C8H18 , Al2(SO4)3

Memorize the charges of common monatomic ions using periodic table Grp 1 elements +1 charge Grp 2 +2 charge Grp 13 +3 charge Grp 14 +2 or +4 charge Grp 15 -3 charge Grp 16 -2 charge Grp 17 -1 charge Grp 18 0 charge

Grp 3 to Grp 12 Transition Metals have varying positive charge. These 3 ions do not vary in charge: Ag+1, Cd+2, Zn+2 H+1 OR H-1

Naming Monatomic Ions Positive Ions – use element name and add word ion Ex. K+1 potassium ion Ions with varying positive charge have a roman number after the name to indicate the charge of the ion Ex. Fe+2 iron(II) ion OR Fe+3 iron(III) ion Pb+2 lead(II) ion OR Pb+4 lead(IV) ion

Negative Ions Negative Ions – use root name (drop last syllable) + -ide ion Examples: F-1 fluoride ion Note: H-1 hydride ion O-2 oxide ion

Binary Cmpds Binary Cmpds – cmpds with only two different elements

Writing Ionic Cmpds Steps: Write symbol and charge of positive ions first. Write symbol and charge of negative ion next. Use subscripts if more than one ion is needed to make the total charge of the cmpd zero.

Examples Write formula for each cmpd: Aluminum oxide Calcium chloride Potassium sulfide Gold (IV) oxide Prac. P207 and p209

Polyatomic Cmpds Cmpds with polyatomic ions – use parentheses when more than one set of polyatomic ion is needed. Examples Tin(IV) sulfate Calcium chlorate Magnesium phosphate Prac p211

Naming Ionic Cmpds Name cation, roman numeral, name anion (if needed) Examples: Name LiH Na2SO4 MgCl2 CuCl2 Al2(SO4)3

Binary Molecular Cmpd. Naming Binary Molecular Cmpd – only 2 elements in formula Memorize the Greek prefixes for one to ten p212 Mono, di, tri, tetra, penta, hexa, hepta, octa, nona, deca 1 2 3 4 5 6 7 8 9 10

Molecular Cmpds. Less electronegative element (more metallic first), and prefix to element to show number of atoms. Omit mono- for the first element. Add prefix to root name of second element and add –ide ending.

Examples: Name P4O10 N2O NO NO2 N2O3 N2O4 N2O5 Prac p213

Covalent Network Cmpds Atoms covalently bonded to its neighbors in a 3D network Ex. SiC Illustrate

Acids Acid – compounds with the hydrogen ion, H+1 , first in the formula

Hydrogen Anion Acid Name -ate -ic acid -ite -ous acid -ide hydro- -ic acid Ex. Hydrogen sulfate ________ hydrogen sulfite ________ hydrogen sulfide ________ (note: ur added in for S and added in for P) Section Review p215

Using Chemical Formulas Formula mass – sum of all masses of atoms in formula Ex: formula mass of: a. Fe b. O2 c. H2O d. C12H22O11 Practice p222

Molar Mass Molar Mass – mass in grams of one mole of a substance Ex. Determine the molar mass of: a. Fe b. O2 c. H2O d. C12H22O11 Practice p223

Formula Mass Vs. Molar Mass Note: The only difference between formula mass and molar mass is the unit of amu and grams.

Mass to Moles Problem: Convert 2.34 X103 g of carbon to moles. Convert 14.6 g of H2O to moles. Prac. P226 #1

Mass to Number of Particles Problem: Convert 2.052 X10-2 moles of carbon to atoms. Change 340.1 moles of water to molecules. How many formula units is 2.985 X10-3 moles of NaCl?

Mass to Number of Particles Problems: Convert a 14.3 g carbon, charcoal briquette, to atoms of C. How many molecules of C13H18O2, ibuprofen, is in the bottle of 206.29g?

How much of table salt must be measured out to give 4 How much of table salt must be measured out to give 4.82 X1025 formula units of NaCl? Prac p226 #2,3

Percent Composition Percent Composition – percentage by mass of each element in the cmpd From sample amts: Mass of element in sample X 100=% E in cmdp mass of sample Ex:

From formula: Mass of E in 1 mol of cmpd X 100=% E in cmdp molar mass of cmpd Prac. Find the % composition of Cu2S. Prac p228

Formulas Empirical Formula – smallest whole number ratio of atoms in a compd. Ex. HCl, H2O Molecular Formula – actual formula of a molecule of compd – some multiple of the empirical formula Ex. HCl, C2H4

Determine which is empirical and molecular formulas: P2O5 NH3 C6H6 Ca(OH)2

Determining Empirical Formulas from Quantitative Analysis: Convert % info to grams. Convert grams to moles of element Get whole number ratios by dividing by smallest # of moles.

Ex. Find the empirical formula of a compd with 32.38% Na, 22.65% S, and 44.99% O. Prac p231

Molecular Formula Calculation of Molecular Formula: x(EF) = MF MF mass = x EF mass Problem must provide the molar mass of the compd from experimental data.

Ex. A compd of phosphorus and oxygen has an empirical formula of P2O5. The molar mass is determined to be 283.89 g. What is the molecular formula? Prac p233 and section review p233