CHEM 1070 Week 3 Notes
CHEM 1070 Week 3 Notes CHEM-1070-40
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This 3 page Class Notes was uploaded by Dkrefft on Friday September 11, 2015. The Class Notes belongs to CHEM-1070-40 at Tulane University taught by Lopreore, Courtney in Fall 2015. Since its upload, it has received 170 views. For similar materials see General Chemistry I in Chemistry at Tulane University.
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Date Created: 09/11/15
Chemistry 1070 Week 3 99 Notes Percent composition 0 Consider C2HBrClF3 Molar mass197382 gmol There are two moles of C one mole of H one mole of Br one mole of Cl and three moles of F What is the mass percent composition Find the molar mass Determine the number of the given element 2 mol C x 12011 mol c 9 x 100 1217 C 197382g C2HBTClF3 051 H 4048 Br 1796 CI 2888 F convert 130 grams OOOO OOOO x 100 composition total grams Determining empirical and molecular formulas from experimentally determined percent composition 0 4477 C o 755 H 0 4771 O 5 step approach take 100 g as the sample size convert the masses of the elements in 100g sample to moles 4477 g C x quot0 3727 mol C 12011gC 1mm 746 mol H 1008g 7529 H x 4771g 0 x quot0 2982 mol 0 15999g Write tentative formula based on numbers just determined in step two C3727H746 02982 Carbon is always first Write the formula in the order that the elements are given to you Attempt to convert the subscripts into whole numbers by dividing all of them by the smallest one C 5 HZ393 20 3 999 125H250 If one or more is still not a whole number multiply the subscripts by something that will make them whole C4x125H4x25004x1 C5H1004 If you pick a multiplier that is too big you may have to reduce it To determine the molecular formula we need to know the mass of a sample that was determined experimentally molar mass number of emperlcal units in one molecule emperlcal mass multiply all of the subscripts in the empirical formula by that number to get the molecular formula Sorbitol molecular mass 182gmol experimentally determined Mass composition of 3956 C 774 H 5270 0 1 mol 3956g C x 329 12011g 774g H x quot0 768 1008g 5270g 0 x quot0 329 15999g C3223 113752698 0333223 999012330 C1x3H233x301x3 9995311703 3120171008315999 91 1gmol 182 2 91 Combustion analysis CxHyOz O2 9 xCO2 y2 H20 After combustion all C atoms are found in CO2 all H atoms in H20 Oxygen has to be determined indirectly Combustion of a 1152g sample of isobutyl propionate yields 2726g CO2 1116g H20 What is the empirical formula Determine mass of C in CO2 by converting to moles of C 9 grams of C 1 mol C02 1 mol C 12011 2726x g 0744g C 44g C02 1 mol C02 1 mol Make a note of how many moles of carbon you have You know this in the second to last step 0620 mol C Do the same for hydrogen 1116g H20x quot0 18011g 01249 mol H molecular formula C6H1406 2molH 1mol H20 1008g 1 mol 01259 H m 1070 Notes 911 Che NQSJ PPONT Determine O indirectly 1152g07441g01249g 0283g O Convert grams of O to moles of O 0283g 0 x quot0 00177 mol 15999g 68816729H861273308s8117777 35H70 9 9 9 C7H1402 Oxidation States Oxidation state refers to how many electrons an atom can either gain or lose when forming a compound the rules are stated on page 85 Use the rules in order Rules The oxidation state of individual atoms is zero The total oxidation state of all atoms in a neutral compound is zero HC0 NOB 1 Group 1 metals have an oxidation state of 1 group 2 2 In its compounds fluorine is 1 In its compounds hydrogen usually has an oxidation state of 1 In a compound oxygen has an oxidation state of 2 Binary element compounds with metals group 17 has 1 group 16 has 2 group 15 has 3 You can figure it out based on the location in the periodic table They all want to be noble gases they act in octets ie Na will lose Cl will gain P4 9 0 Al203 9 2Al 32 0 so Al 3 MnO4 9 4x 2 Mn 1 so Mn 7 Memorize the rules so you can use them in order Naming Binary compound of metals and nonmetals modify the end of the nonmetal with ide Calcium bromide magnesium iodine Al203 aluminum oxide In both the formula and the name write the element with the positive oxidation state first HCI hydrogen chloride Write forms for Lithium oxide Li20 Tin ll fluoride SnF2 Lithium nitride Li3N
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