Lecture 79/14/05

Ionic Compounds continued Ions in the compounds are in a crystal lattice Formula unit  Smallest whole number ratio of cations/anions Characteristics  High melting and boiling point  Many soluble in water  Forms electrolytes when dissolved in water

Naming ionic compounds Name of the cation, then name of anion NaCl (NH 4 ) 2 CO 3 CuO Aluminum nitrate Potassium chloride Iron (III) bromide

Molecular compounds Non-ionic compounds Formed from 2 or more nonmetals Many are insoluble in water  Many ARE soluble in organic liquids though Lower boiling and melting points

Naming molecular compounds (Binary compounds) Hydrogen + nonmetal  HF - hydrogen fluoride  H 2 S – dihydrogen sulfide Put elements in order of increasing group number  NF 3 – Nitrogen trifluoride  CO – Carbon monoxide  SF 6 – Sulfur hexafluoride Many have common names (p. 96)  CH 4 – methane  H 2 O – water  NH 3 – ammonia

What is the molar mass of ethanol, C 2 H 6 O? 1 mol ethanol contains: 2 mol C (12.01 g C/1 mol) = g C 6 mol H (1.01 g H/1 mol) = 6.06 g H 1 mol O (16.00 g O/1 mol) = g O TOTAL = molar mass = g/mol

Percentages The solder once used by plumbers to fasten copper pipes together consists of 67% lead and 33% tin. What is the mass of lead in a 250-g block of solder?

PERCENT WEIGHT A pure compound always consists of the same elements combined in the same proportions by weight. What is the percentage of each element in ethanol (C 2 H 6 O)? Ethanol, C 2 H 6 O 52.13% C 13.15% H 34.72% O