Dr. S. M. Condren Chapter 3 Molecules, Ions, and their Compounds.
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Transcript of Dr. S. M. Condren Chapter 3 Molecules, Ions, and their Compounds.
Dr. S. M. Condren
Chapter 3
Molecules, Ions,
and their
Compounds
Dr. S. M. Condren
Structure Determination of DNA
http://mrsec.wisc.edu/Edetc/background/DNA/index.html
Dr. S. M. Condren
DNA
Dr. S. M. Condren
NaCl, saltNaCl, saltNaCl, saltNaCl, salt
Buckyball, CBuckyball, C6060
Ethanol, CEthanol, C22HH66OO
Molecules, Ions& Their Compounds
Dr. S. M. Condren
• Formula for glycine is Formula for glycine is CC22HH55NONO22
• In one molecule there areIn one molecule there are
–2 C atoms2 C atoms
–5 H atoms5 H atoms
–1 N atom1 N atom
–2 O atoms2 O atoms
MOLECULAR FORMULAS
Dr. S. M. Condren
Some Common Molecules
Dr. S. M. Condren
ExampleHow many moles of ethyl alcohol (ethanol,
C2H6O) are in a “standard” can of beer if there are 21.3 g of C C22HH66O?O?
MM = 46.069 g/mol
#mol = (21.3 g)(1 mol/46.069 g)= 0.462 mol
Dr. S. M. Condren
ExampleHow many molecules of ethyl alcohol
(ethanol, C2H6O) are in a “standard” can of beer if there are 21.3 g of C C22HH66O?O?
MM = 46.069 g/mol
#mol = 0.462 mol# molecules = (0.462 mol)
(6.022x1023 molecules/mol)= 2.78x1023 molecules
Dr. S. M. Condren
ExampleHow many C atoms are in a “standard” can
of beer if there are 21.3 g of C C22HH66O?O?
MM = 46.069 g/mol
#mol = 0.462 mol# molecules = 2.78x1023 molecules
#C atoms = (2.78x1023 molecules)(2 C atoms/molecule C2H6O)
= 5.57x1023 C atoms
Dr. S. M. Condren
Molecular & Ionic Compounds
HemeHeme NaClNaCl
Fe
N
Dr. S. M. Condren
Lithium Fluoride
Dr. S. M. Condren
+3
-4 -1-2-3+1
+2
By losing or gaining e-, atom has same By losing or gaining e-, atom has same number of e-’s as nearest Group 8A atom.number of e-’s as nearest Group 8A atom.
Charges on Common Ions
Dr. S. M. Condren
Announcement
• Lab Safety Quiz must be completed by start of lab tomorrow with a perfect score
• You can retake as many times as necessary
• Lake Study is due on Friday
Dr. S. M. Condren
AnnouncementATTN CHEMISTRY STUDENTS: Need a
Tutor? Visit the GUTS DROP IN CENTER for FREE CHEMISTRY TUTORING! Where: 1ST FLOOR OF COLLEGE LIBRARY When: Sundays, 2pm-8pm, Mondays-Wednesdays, 2pm-6pm Just stop by and work with a tutor on homework or exam prep! No registration necessary. Detailed schedule: http://
guts.studentorg.wisc.edu/dropinsummerschedule.htm With any other questions email the GUTS Office at [email protected] or visit the website: http://guts.studentorg.wisc.edu
Dr. S. M. Condren
Predicting Charges on Monatomic Ions
Dr. S. M. Condren
Ion Formation
Reaction of aluminum and bromine
Dr. S. M. Condren
Dr. S. M. Condren
Combustion Analysis
Dr. S. M. Condren
Percentage Composition
description of a compound based on the relative amounts of each element in the compound
Dr. S. M. Condren
EXAMPLE: What is the percent composition of chloroform, CHCl3, a substance once used as an anesthetic?MM = 1(gaw)C + 1(gaw)H + 3(gaw)Cl
= (12.011 + 1.00797 + 3*35.453)amu
= (12.011 + 1.00797 + 106.36)amu
= 119.38amu
1(gaw)C 1(12.011)%C = ----------- = ------------ X 100 = 10.061% C
119.38 119.38
Dr. S. M. Condren
EXAMPLE: What is the percent composition of chloroform, CHCl3, a substance once used as an anesthetic?MM = 1(gaw)C + 1(gaw)H + 3(gaw)Cl
= (12.011 + 1.00797 + 3*35.453)amu
= 119.38amu
1(1.00797)H%H = ---------------- X 100 = 0.84436% H 119.38
Dr. S. M. Condren
EXAMPLE: What is the percent composition of chloroform, CHCl3, a substance once used as an anesthetic?MM = 1(gaw)C + 1(gaw)H + 3(gaw)Cl
= (12.011 + 1.00797 + 3*35.453)amu
= 119.38amu
3(35.453)Cl%Cl = ----------------- X 100 = 89.095% Cl
119.38
Dr. S. M. Condren
EXAMPLE: What is the percent composition of chloroform, CHCl3, a substance once used as an anesthetic?MM = 1(gaw)C + 1(gaw)H + 3(gaw)Cl
= 119.377amu
%C = 10.061% C
%H = 0.84436% H
%Cl = 89.095% Cl
Dr. S. M. Condren
Simplest (Empirical) Formula
formula describing a substance based on the smallest set of subscripts
Dr. S. M. Condren
Acetylene, C2H2, and benzene, C6H6, have the same empirical formula. Is the correct empirical formula:
C2H2
CH
C6H6
Dr. S. M. Condren
EXAMPLE: A white compound is formed when phosphorus burns in air. Analysis shows that the compound is composed of 43.7% P and 56.3% O by mass. What is the empirical formula of the compound?
Element % (%/gaw)
P
O
43.7
56.3
43.7/30.97 = 1.41
56.3/15.9994 = 3.52
Divide bySmaller
1.41/1.41
= 1.00
3.52/1.41= 2.50
Multiplyby Integer
2*1.00
2*2.50
2
5
Empirical Formula => P2O5
Dr. S. M. Condren
Never round-off these numbers
Always round-off here
Example When analyzed, an unknown compound gave these experimental results: C, 54.0%; H, 6.00%, and O, 40.0%. Four different students used these values to calculate the empirical formulas shown here. Which answer is correct? Why did some students not ge the correct answer? (a) C4H5O2 (b) C5H7O3 (c) C7H10O4 (d) C9H12O5
Dr. S. M. Condren
EXAMPLE: A sample of a brown-colored gas that is a major air pollutant is found to contain 2.34 g of N and 5.34 g of O. What is the empirical formula of the compound?
5.34%O = ----------------- X 100 = 69.5% O
2.34 + 5.34
2.34 %N = ----------------- X 100 = 30.5% N 2.34 + 5.34
Dr. S. M. Condren
EXAMPLE: A sample of a brown-colored gas that is a major air pollutant is found to contain 2.34 g of N and 5.34 g of O. What is the empirical formula of the compound?%N = 30.5% N %O = 69.5% O
Element % (%/gaw)
N 30.5 30.5/14.0067 = 2.18
O 69.5 69.5/15.9994 = 4.34
Divide by Smaller2.18/2.18 = 1.00
4.34/2.18 = 1.99
1
2
Empirical Formula => NO2
x1=
x1=
Dr. S. M. Condren
Molecular Formula
the exact proportions of the elements that are formed in a molecule
Dr. S. M. Condren
Molecular Formula from Simplest Formula
empirical formula => EF
molecular formula => MF
MF = X * EF
Dr. S. M. Condren
Molecular Formula from Simplest Formula
formula mass => FM
sum of the atomic weights represented by the formula
molar mass = MM = X * FM
Dr. S. M. Condren
Molecular Formula from Simplest Formula
first, knowing MM and FM
X = MM/FM
then
MF = X * EF
Dr. S. M. Condren
EXAMPLE: A colorless liquid used in rocket engines, whose empirical formula is NO2, has a molar mass of 92.0. What is the molecular formula?
FM = 1(gaw)N + 2(gaw)O = 46.0
MM 92.0X = ------- = -------- = 2 FM 46.0
thus MF = 2 * EF
Dr. S. M. Condren
What is the correct molecular formula for this colorless liquid rocket fuel?
2NO2
NO2
N2O4
Dr. S. M. Condren
Example: A 100.00 g sample of CuSO4.XH2O was
strongly heated to drive off the waters of hydration. After the heating, the sample weighed 63.92 g. What is the value of X? the formula of the hydrated compound?
= 2.002 mol H2O
(1 mol H2O/18.02g H2O)(36.08g H2O)#mol H2O == 36.08g water= 100.00g – 63.92g
- #g anhydrous#g hydrate#g water =
#mol CuSO4 = (63.92g CuSO4)(1 mol CuSO4/159.6 g CuSO4)
= 0.4005 mol CuSO4
X= (2.002 mol H2O/0.4005 mol CuSO4) = 5
Thus CuSO4.5H2O