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Week II Recitation problems_1

# Week II Recitation problems_1 - other isotope 108.9049 amu...

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Recitation problems II (Anyone is free to suggest any discussion topics) 1. Avogadro’s number: number of molecules, Formula weights, atoms a. How many moles of atoms are there in 7.760 x 10 11 He atoms? 1.289 x 10 -12 He atoms b. How many atoms are there in 3.355 x 10 -4 moles of SF 6 molecules ? Hint: two step process: 1.414 x 10 21 atoms c. How many molecules are in 1.266 x 10 -3 mol of SO 2 molecules? 7.624 x 10 20 molecules SO 2 d. How moles of AlCl 3 are in 4.1236 Formula units? 6.8476 x 10 -24 moles AlCl 3 2. Atomic numbers, mass numbers a. How many neutrons do the following atoms have? Cl-35, (18) U -235 (143), C- 14 (8), F-19 (10) b. Strontium has four isotopes with the following masses and their relative abundances 83.9134 amu (0.56 %), 85.9094 amu (9.86%), 86.9089 amu (7.00%) and 87.9056 amu (82.58 %). Calculate the atomic mass of strontium. 87.6166 amu c. Naturally occurring silver (Ag) consist of two isotopes. One of the isotopes has a mass of 106.90509 amu and 51.84 % abundance. What is the atomic mass of the

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Unformatted text preview: other isotope? 108.9049 amu 3. Molecular weight and Stoichiometry calculations . a. Saccharin an artificial sweetener which has the composition 45.90 % C , 2.75 % H , 26.20% O, 17.50 % S and 7.65 % N. What is the empirical formula for saccharin? C 7 H 5 O 3 SN b. A gaseous mixture containing 4.15 mol of Hydrogen gas and 7.13 mol of Oxygen react to form steam (H 2 O). i) Write a balanced equation? ii) What is the limiting reagent? Hydrogen iii) What is the theoretical yield? 74.7 g H 2 O iv) How many moles of excess reagent remain unreacted? 5.06 moles O 2 c. Aluminum reacts with sulfur to form aluminum sulfide (Al 2 S 3 ). Initially 1.18 mol of Aluminum and 2.25 mol of sulfur are combined. i) Write a balanced equation? ii) What is the limiting reagent? Al iii) What is the theoretical yield? 88.7 g Al 2 S 3 iv) How many moles of excess reagent remain unreacted? 0.48 moles S...
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Week II Recitation problems_1 - other isotope 108.9049 amu...

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