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Dr. S. M. Condren Chapter 3 Molecules, Ions, and their Compounds.

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Presentation on theme: "Dr. S. M. Condren Chapter 3 Molecules, Ions, and their Compounds."— Presentation transcript:

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2 Dr. S. M. Condren Chapter 3 Molecules, Ions, and their Compounds

3 Dr. S. M. Condren Structure Determination of DNA

4 Dr. S. M. Condren DNA

5 Dr. S. M. Condren NaCl, salt Buckyball, C 60 Ethanol, C 2 H 6 O Molecules, Ions & Their Compounds

6 Dr. S. M. Condren Formula for glycine is C 2 H 5 NO 2Formula for glycine is C 2 H 5 NO 2 In one molecule there areIn one molecule there are –2 C atoms –5 H atoms –1 N atom –2 O atoms MOLECULAR FORMULAS

7 Dr. S. M. Condren Some Common Molecules

8 Dr. S. M. Condren Example C 2 H 6 O? How many moles of ethyl alcohol (ethanol, C 2 H 6 O) are in a standard can of beer if there are 21.3 g of C 2 H 6 O? MM = g/mol #mol = (21.3 g)(1 mol/ g) = mol

9 Dr. S. M. Condren Example C 2 H 6 O? How many molecules of ethyl alcohol (ethanol, C 2 H 6 O) are in a standard can of beer if there are 21.3 g of C 2 H 6 O? MM = g/mol #mol = mol # molecules = (0.462 mol) (6.022x10 23 molecules/mol) = 2.78x10 23 molecules

10 Dr. S. M. Condren Example C 2 H 6 O? How many C atoms are in a standard can of beer if there are 21.3 g of C 2 H 6 O? MM = g/mol #mol = mol # molecules = 2.78x10 23 molecules #C atoms = (2.78x10 23 molecules) (2 C atoms/molecule C 2 H 6 O) = 5.57x10 23 C atoms

11 Dr. S. M. Condren Molecular & Ionic Compounds Heme NaCl Fe N

12 Dr. S. M. Condren Lithium Fluoride

13 Dr. S. M. Condren By losing or gaining e-, atom has same number of e-s as nearest Group 8A atom. Charges on Common Ions

14 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

15 Dr. S. M. Condren Announcement ATTN 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: With any other questions the GUTS Office at or visit the website:

16 Dr. S. M. Condren Predicting Charges on Monatomic Ions

17 Dr. S. M. Condren Ion Formation Reaction of aluminum and bromine

18 Dr. S. M. Condren

19 Combustion Analysis

20 Dr. S. M. Condren Percentage Composition description of a compound based on the relative amounts of each element in the compound

21 Dr. S. M. Condren EXAMPLE: What is the percent composition of chloroform, CHCl 3, a substance once used as an anesthetic? MM = 1(gaw) C + 1(gaw) H + 3(gaw) Cl = ( *35.453)amu = ( )amu = amu 1(gaw) C 1(12.011) %C = = X 100 = % C

22 Dr. S. M. Condren EXAMPLE: What is the percent composition of chloroform, CHCl 3, a substance once used as an anesthetic? MM = 1(gaw) C + 1(gaw) H + 3(gaw) Cl = ( *35.453)amu = amu 1( ) H %H = X 100 = % H

23 Dr. S. M. Condren EXAMPLE: What is the percent composition of chloroform, CHCl 3, a substance once used as an anesthetic? MM = 1(gaw) C + 1(gaw) H + 3(gaw) Cl = ( *35.453)amu = amu 3(35.453) Cl %Cl = X 100 = % Cl

24 Dr. S. M. Condren EXAMPLE: What is the percent composition of chloroform, CHCl 3, a substance once used as an anesthetic? MM = 1(gaw) C + 1(gaw) H + 3(gaw) Cl = amu %C = % C %H = % H %Cl = % Cl

25 Dr. S. M. Condren Simplest (Empirical) Formula formula describing a substance based on the smallest set of subscripts

26 Dr. S. M. Condren Acetylene, C 2 H 2, and benzene, C 6 H 6, have the same empirical formula. Is the correct empirical formula: C 2 H 2 CH C 6 H 6

27 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 /30.97 = / = 3.52 Divide by Smaller 1.41/1.41 = /1.41 = 2.50 Multiply by Integer 2*1.00 2* Empirical Formula => P 2 O 5

28 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) C 4 H 5 O 2 (b) C 5 H 7 O 3 (c) C 7 H 10 O 4 (d) C 9 H 12 O 5

29 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 %N = X 100 = 30.5% N

30 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 / = 2.18 O / = 4.34 Divide by Smaller 2.18/2.18 = /2.18 = Empirical Formula => NO 2 x1=

31 Dr. S. M. Condren Molecular Formula the exact proportions of the elements that are formed in a molecule

32 Dr. S. M. Condren Molecular Formula from Simplest Formula empirical formula => EF molecular formula => MF MF = X * EF

33 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

34 Dr. S. M. Condren Molecular Formula from Simplest Formula first, knowing MM and FM X = MM/FM then MF = X * EF

35 Dr. S. M. Condren EXAMPLE: A colorless liquid used in rocket engines, whose empirical formula is NO 2, has a molar mass of What is the molecular formula? FM = 1(gaw) N + 2(gaw) O = 46.0 MM 92.0 X = = = 2 FM46.0 thus MF = 2 * EF

36 Dr. S. M. Condren What is the correct molecular formula for this colorless liquid rocket fuel? 2NO 2 NO 2 N 2 O 4

37 Dr. S. M. Condren Example: A g sample of CuSO 4. XH 2 O was strongly heated to drive off the waters of hydration. After the heating, the sample weighed g. What is the value of X? the formula of the hydrated compound? = mol H 2 O (1 mol H 2 O/18.02g H 2 O)(36.08g H 2 O)#mol H 2 O = = 36.08g water = g – 63.92g - #g anhydrous#g hydrate #g water = #mol CuSO 4 = (63.92g CuSO 4 ) (1 mol CuSO 4 /159.6 g CuSO 4 ) = mol CuSO 4 X=(2.002 mol H 2 O/ mol CuSO 4 ) = 5 Thus CuSO 4. 5H 2 O


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