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B. Experimentally Determining the Empirical Formulas for Compounds 1. Calculating Percent Composition
2. Mass Percent in Chemical Compounds What is the mass % of O in the OH radical?
What is the mass% of H in the OH radical?
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What is the mass % of H2O in Na2SO4·4H2O?
Molar Mass of Na2SO4·4H2O
Molar Mass of Na2SO4·4H2O Mass % of H2O in Na2SO4·4H2O Mass % of H2O in Na2SO4·4H2O = 33.6571¦70% = 33.6571%
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How do we Determine Empirical Formulas? 1. Determine the mass of each element present in the compound. - if given mass % of all but one compound 100% = mass % A + mass % B + …
- if given mass percent composition, assume you have exactly 100 grams of the compound
2.
Convert mass to number of moles present for each atom.
3.
Find the smallest ratio of each atom to all of the other atoms.
https://i.ytimg.com/vi/DT-uMyXWwek/movieposter.jpg
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How do we Calculate Empirical Formulas? Cont’d Calculated E.F.
Multip. Factor
New E.F.
Other Sub. Use
C1H1.5
2
C2H3
(0.5, 1.5, 2.5, etc)
C1H1.33
3
C3H4
(0.33, 1.33, etc)
C1H1.25
4
C4H5
(0.25, 1.25, etc)
C1H1.66
3
C3H5
(0.66, 1.66, etc)
C1H1.75
4
C4H7
(0.75, 1.75, etc)
How do we get molecular formulas from empirical formulas? How many sticks of gum in a pack of gum?
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Example 4. Putrescine, an incredibly foul smelling compound that is generated during the decomposition of flesh, contains nitrogen, hydrogen, and carbon. In some deleted footage recently shown on Talking Dead, Rick and Carl tried to synthesize putrescine to use it as a zombie masking agent. In order to obtain the chemical formula of putrescine, Rick and Carl analyzed a sample of putrescine and found it contained 34.13|39% N and 58.50|97% C. What is the empirical formula for putrescine?
http://images.amcnetworks.com/amc.com/wp-content/uploads/2015/10/the-walking-dead-episode-601-daryl-reedus-post-1600x600.jpg, http://media.vanityfair.com/photos/568c0baa396977000bddd977/master/w_900,c_limit/walking-dead-kill-off-cast.jpg
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Example 4 Work Determine the mass of each element present in the compound.
Convert mass to number of moles present for each atom.
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Find the smallest ratio of each atom to all of the other atoms.
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Special Type of Empirical Formula Problem - Combustion Analysis of HC or Oxygenated HC to obtain empirical Formula HxCy or HxCyOz + O2(g) CO2(g) + H2O(g)
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Example Problems 5. Menthol is composed of C, H, and O. A 0.1005 g sample of menthol is combusted producing 0.2829 g of CO2 and 0.1159 g of H2O. What is the empirical formula of menthol?
If the molar mass of menthol is 156 g/mol, what is its molecular formula?
6. A 1.562 g sample of the hydrocarbon C7H16 is burned in an excess of oxygen. What masses of CO2 and H2O should be obtained?
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III. Naming Chemical Compounds A. Naming Inorganic and Simple Organic Compounds Organic Cmpds.
Inorganic Cmpds.
Cmpd. formed from primarily C and H or C, H, N, O, and small amounts of other elements All other compounds
1. Ionic Compounds (Metal + Nonmetal or Metal + Polyatomic Ion) Name -
Formula -
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Rules for Names I. Name of Cation Most Main Group Metals Plus Ag, Zn, and Cd
-
Most Transition Metals and Some Group 13-16 Metals -
II. Name of the non-metal with an –ide ending or name of the polyatomic ion nitrogen chlorine oxygen chlorate (Memorize table pg 12 GCN) http://www.mwsd.cc/webpages/mcallender/imageGallery/pblock21.jpg
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Formula Name (first identify cation and anion with formulas)
Formula KBr
Sr3(PO4)2
Al(IO)3
Ba3P2
Cation
Anion
Name
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Rules for Formulas I.
Electrically neutral - balance charge #’s as subscrpts Name lithium oxide
aluminum sulfate copper(II) chloride calcium periodate
ammonium nitride
Cation
Anion
Formula
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2.
Binary Molecular Compounds (nonmetal + nonmetal)
Need greek prefixes 1 - mono
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-
octa
2
-
di
9
-
nona
3
-
tri
10 -
deca
4
-
tetra
5
-
penta
6
-
hexa
7
-
hepta
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Rules for Names 1. numbers of atoms given by greek prefixes (mono not used for first named element) 2. element farthest to the left written first (exception: oxygen usually written last when combined with F) 3. elements in same group lowest one first 4. second element –ide ending 5. if element starts with a or o, a or o is dropped from end of Greek prefix
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Examples Formula
Cation
Anion
Name
Cation
Anion
Formula
N2O
SO2
PCl5
Name carbon tetrachloride diboron tetrabromide
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3. Binary Acids Acid -
Binary Acid
Common Binary Acids
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Rules for names 1. name of 2nd element add hydro as prefix and –ic as suffix 2. add word acid at end hydro______ic acid
Examples Formula/Name Cation HBr hydrosulfuric acid
Anion
Name/Formula
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4. Oxoacids (or oxyacids) - adding H to oxoanions NO2-, NO3-, SO32-, SO42-, PO33-, PO43-, IO-, IO2-, IO3-, IO4-, etc.
Increasing #’s of O Ion
___ite ___ate
Acid
___ous
___ic
ADD ACID ENDING
Increasing #’s of O Ion
hypo___ite ___ite ___ate
Acid hypo___ous
___ous
___ic
ADD ACID ENDING
per___ate
per___ic
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Examples Formula/Name Cation H3PO4
HClO
perbromic acid
Anion
Name/Formula
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5. Hydrates CoCl26H2O
https://upload.wikimedia.org/wikipedia/commons/e/ee /Indicating-silica-gel.png
https://upload.wikimedia.org/wikipedia/commons/e/ee/Indicating-silica-gel.png
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C. Naming Organic Compounds
Hydrocarbon –
Types of Covalent bonds
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Alkanes (table 3.7) Prefix – greek and latin and others 1C
2C 3C
4C
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Isomers
Functional Groups - replacing an H on an alkane, alkene, or alkyne, can dramatically change the chemical and physical properties of the organic molecule Functional group – Alcohols
Acids
