Avagadro's Number and the Mole - video-solutions

Avagadro's Number and the Mole - video-solutions - 10 Now...

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nanni (arn437) – Avagadro’s Number and the Mole - video – CNS – (87654) 1 This print-out should have 2 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. 001 10.0 points A 15 g sample oF P 4 O 10 contains how many molecules oF phosphorus pentaoxide? Correct answer: 3 . 1818 × 10 22 molec. Explanation: m P 4 O 10 = 15 g To solve this problem, we will need both the molecular mass oF P 4 O 10 and Avogadro’s number (6 . 022 × 10 23 atoms/mol). ±irst fnd the molecular mass oF P 4 O 10 . Each mole oF P 4 O 10 contains 4 moles oF P (oF atomic mass 30 . 974 g / mol) and 10 moles oF O (oF atomic mass 16 g / mol). Molecular mass oF P 4 O 10 : ? g/mol = (4)(30 . 974 g / mol) + (10)(16 g / mol) = 283 . 896 g/mol Then convert grams oF P 4 O 10 to moles oF P 4 O 10 using the molecular mass: ? mol P 4 O 10 = 15 g P 4 O 10 × 1 mol P 4 O 10 283 . 896 g P 4 O 10 = 0 . 0528362 mol P 4 O
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Unformatted text preview: 10 Now convert moles to the number oF molecules using Avogadro’s number: ? molec P 4 O 10 = 0 . 0528362 mol P 4 O 10 × 6 . 022 × 10 23 P 4 O 10 molec 1 mol P 4 O 10 = 3 . 1818 × 10 22 molec P 4 O 10 002 10.0 points IF one electron weighs 9 . × 10-28 grams, what is the mass oF one mole oF electrons? 1. 5 . × 10-23 grams 2. 1 . 5 × 10-51 grams 3. 5 . 4 × 10-4 grams correct 4. 5 . × 10-24 grams 5. 9 . × 10-18 grams Explanation: m = 9 . × 10-28 g We know one mole oF electrons contains 6 . 022 × 10 23 electrons. Since we know the mass oF an individual electron we can calcu-late the mass oF one mole oF electrons. ? g/mol e-= 9 . × 10-28 g 1 e-× 6 . 022 × 10 23 e-1 mol e-= 5 . 4 × 10-4 g/mol e-...
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This note was uploaded on 09/19/2011 for the course CH 301 taught by Professor Fakhreddine/lyon during the Fall '07 term at University of Texas at Austin.

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