FORMULA WRITING, GFW, % MASS, AND HYDRATES. Say what??

FORMULA WRITING, GFW, % MASS, AND HYDRATES Say what??

Formula Writing Ionic Compounds One metal + one non-metal

Let s Review Fill in the charges

More Review How are ions formed? Positive ions Aka: Negative ions Aka:

Lets Write Some Formulas ions are ALWAYS written first. If more than one ion can exist, use parentheses and the charge in roman numeral form Ie: Cu +2 is named copper (II) ions are ALWAYS written second. So Can two positive ions ever be put together? Can two negative ions ever be put together?

How do you know what numbers to use? Criss-Cross Method Identify the charge of each ion criss-cross the charges ignore the + and Numbers become subscripts Let s do a few examples pick any cation and anion:

Naming Compounds Cation stays the same Anion ending changes to ide Often this simply involves changing the ine ending Chlorine chloride Fluorine fluoride Bromine bromide However, there are some you need to remember: Examples: Phosphorus phosphide Sulfur sulfide Oxygen oxide

Let s do some more practice Ca and Cl Charges Criss Cross Name Ba and O Cu and I

Formula Writing Polyatomic Ion Compounds

Polyatomic Ions Remember: is written first is written second New: Put parentheses around the ion

Naming the Compounds with Polyatomics You need to remember the Polyatomic Ions If single element: cation and anion is the same If polyatomic: use names provided

Some Polyatomic Practice Write the formula the following: Formula Name Ba +2 C 2 H 3 O 2-1 Al +3 PO 4-3 K +1 SO 4-2 Ca +2 NO 3-1

Formula Writing Covalent Molecules 2 non-metals together

Writing Formulas Remember, bonds require 2 electrons Covalent is the sharing of electrons

Naming Covalent Compounds The less electronegative element is written first. Remember the trend (increasing up and to the right) Use a number indicating prefix only if more than one atom is present Ie N 2 is dinitrogen A prefix is always added to the name of the second element Will change ending of name to ide (just like ionic bonds)

Naming Covalent Compounds - Rules Leave the "a" off the end of the prefixes that end in "a" and the o off of mono-if they are placed in front of an element that begins with a vowel. Number Indicating Prefixes: mon(o) -1 di -2 tri -3 tetr(a) - 4 pent(a) -5 hex(a) - 6 hept(a) - 7 oct(a)- 8 non(a) -9 dec(a) -10

Try Some Practice N 2 S 4 Dinitrogen tetrasulfide NI 3 Nitrogen triiodide CCl 4 Carbon tetrachloride P 2 O 5 Diphosphorus pentoxide

Common Names H 2 O - water NH 3 - ammonia CH 4 - methane C 2 H 6 - ethane C 3 H 8 - propane

Formula Weight

Molecular Mass The molecular mass is the same numeric value as the atomic mass but the unit is different Atomic mass is measured in atomic mass units (amu) Molecular mass is measured in grams So molecular mass is the atomic mass with the unit grams or g

Molecular Mass

Formula Weight Formula weight of a compound is the sum of the atomic masses of the atoms As given in the formula of the compound. Sum of molecular masses

Formula Weight Steps: 1. Determine how many moles of each element are in the compound using the subscripts. 2. Find the molecular mass of each element in the compound by multiplying #1 and atomic mass. 3. Add it all together We will use a table that looks like this Element # Atoms Atomic Mass Molecular Mass

Formula Weight~ Example 1. Determine atoms first Subscripts in formula No parentheses moles = subscripts Parenthesizes moles = outer subscript x inner subscript Element # Atoms Atomic Mass Molecular Mass Aluminum 1 Bromine 3

Formula Weight ~ Example 2. To find the molecular mass of aluminum and bromine: 3. Add elements molar masses together to get compounds molar mass: Element # Atoms Atomic Mass Molecular Mass Aluminum 1 26.98 g 26.98 g Bromine 3 79.9 g 239.70 g = 266.68 g/mol AlBr 3

Percent Composition

Percent Composition The percent that you find of any ONE element in a compound of elements. Found by taking the PART that you are looking for and dividing it by the WHOLE. Then multiply by 100 to move decimal.

Percent Composition What percent of 92 is 42? In other words, the part 42 of the whole 92 is what percent? 42/92 x 100 = 45.7%

Percent Composition and Chemistry Now, take the PART (Ca) and divide it by the WHOLE. Multiple by 100. Element # Atoms Molecular Mass % Composition Ca 3 120.24 g 120.24/310.18 x100 = 38.8% P 2 61.95 g O 8 128.00 g = 310.19g/mol

Hydrates

What are hydrates? Hydrates- compounds that contain H 2 O in their structure Different from water because the H 2 O is part of the molecule (not just surrounding it). H2O can usually be removed if heated.

Writing Hydrates A dot separates water e.g. CuSO 4 5H 2 O is copper(ii) sulfate pentahydrate. Naming- use prefix to show how many H 2 O are present mono - 1 di - 2 tri- 3 tetra - 4 penta- 5 hexa 6 hepta 7 octa - 8 nona - 9 deca- 10

Examples Na 2 SO 4 10H 2 O sodium sulfate decahydrate NiSO 4 6H 2 O nickel(ii) sulfate hexahydrate sodium carbonate monohydrate Na 2 CO 3 H 2 O barium chloride dihydrate BaCl 2 2H 2 O

Hydrate Uses Chloral Hydrateprescription drug that is used for the short-term treatment of insomnia. Terpin hydrate helps to loosen mucus Ice That Burns: Gas Hydrates Offer a Potential Energy Reserve, Danger to Petroleum Exploration & Global Warming Concern As the methane diffuses through the sediment, it combines with water at the low temperatures and high pressures beneath the ocean to produce an ice-like solid.

More Hydrate Uses A colorful example is cobalt(ii) chloride, which turns from blue to magenta (red) upon hydration, and can therefore be used as a water indicator.