AP Chem Turn in Chromatography Lab. Today: Mole, EF & MF Review Due Dates: Unit 1 MC Packet due Wed 9/12 Unit 1 Test Th 9/13 and Fri 9/4

Definitions One Mole = 6.022 x 1023 particles This is Avogadro’s number. Molar Mass: The mass of one mole of a substance in grams. Percent Composition: Identifies the elements present in a compound as a mass % of the total compound mass

Molar Mass & Percent Composition 108.996 grams 342.14 grams 101.11 grams 47.70 % Cr 52.30 % F 15.77% Al 28.11% S 56.12 % O 38.67% K 13.86% N 47.47% O *Remember: multiply the subscripts when there is a parentheses

Molar Conversions Conversion Factors: Convert between grams, moles, and molecules using dimensional analysis Conversion Factors: 1 𝑚𝑜𝑙𝑒 ___𝑔𝑟𝑎𝑚𝑠 or ____𝑔𝑟𝑎𝑚𝑠 1 𝑚𝑜𝑙𝑒 (Molar Mass) 1 𝑚𝑜𝑙𝑒 6.022 𝑥 10 23 𝑚𝑜𝑙𝑒𝑐𝑢𝑙𝑒𝑠 or 6.022 𝑥 10 23 𝑚𝑜𝑙𝑒𝑐𝑢𝑙𝑒𝑠 1 𝑚𝑜𝑙𝑒

41.98 gNaF 4.5 mol NaF = 189 g NaF 1 mol NaF

Molar Conversions How many grams are in 4.5 moles of sodium fluoride, NaF? 189 grams How many moles are in 98.3 grams of aluminum hydroxide, Al(OH)3? 1.26 mol How many molecules are there in 450 grams of sodium sulfate, Na2SO4? 1.91 x 1024 molecules How many grams are there in 7.5 x 1023 molecules of sulfuric acid, H2SO4? 122 grams

Empirical vs. Molecular Formula Empirical Formula = simplest/smallest ratio of each element in a compound Molecular Formula = total number of atoms of each element in a compound Remember: the empirical and molecular formula can be the same!

C4H7 CH2 C6H12 84/14 = 6 14.03 g/mol

CaCl2 C4H8O4 C2F6

Mass Spectrometer Analyzes Samples by Mass and % Composition

Mass Spectrometer Signal for Neon *you need to analyze the data!

1 mol C C: H: O: 3.758 g C = 0.3129 mol C 12.01 g C 1 mol H 0.316 g H =0.3129 mol H 1.01 g H 1 mol O 1.251 g O =0.0782 mol O 16.00 g O

0.3129 mol C = 4 mol C 0.0782 mol 0.3129 mol H = 4 mol H C4H4O 0.0782 mol 0.0782 mol O = 1 mol O 0.0782 mol

Practice C4H4O CaO2H2 ( Ca(OH)2 )

1 mol Fe Fe: S: 63.52 g Fe = 1.137 mol Fe 55.85 g Fe 1 mol S 36.48 g S =1.138 mol S 32.06 g S

Practice FeS A) C2H4O B.)C6H12O3

25.94% N 74.06% O. Determine Empirical Formula 25.94 𝑔 𝑁 × 1 𝑚𝑜𝑙𝑒 𝑁 14.01 𝑔 𝑁 74.06 𝑔 𝑂 × 1 𝑚𝑜𝑙𝑒 𝑂 16.00 𝑔 𝑂 =1.85 mole N =4.63 mole O 1.85 mole N What happens when you divide and you don’t get a whole number? =1 N 1.85 mole 4.63 mole O =2.5 O 1.85 mole

“NO2.5” We need to multiply the entire thing by a whole number so that we can get whole number subscripts NO2.5 x 2 = N2O5

What happens if you don’t get whole number mole ratios? If when you divide all the # of moles by the smallest # of moles and your mole ratios end in: Multiply all mole ratios by ____ to get all whole numbers for your mole ratio ~0.5 (1/2) X 2 ~.33 (1/3) , ~.66 (2/3) X 3 ~0.25 (1/4), ~0.75 (3/4) X 4