122ch13c - 27 13.36) a) Note the denominator in mass % is...

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27 13.36) a) Note the denominator in mass % is the total mass of solution Total mass = mass solute + mass solvent mass solute mass % = ------------------------ x 100% total mass solution 253.80 g I 2 ? mass I 2 = 0.035 mol I 2 x --------------- = 8. 8 83 g I 2 1 mol I 2 8. 8 83 g I 2 mass % I 2 = -------------------------------- x 100% (8. 8 83 g I 2 + 115 g CCl 4 ) = 7. 1 70 % = 7.2 % I 2 Note : Think of % as parts per hundred (it makes ppm, ppb and ppt easier to understand). b) mass solute ppm = ------------------------ x 10 6 total mass solution 0.0079 g Sr 2+ ppm Sr 2+ = -------------------------------- x 10 6 = 7. 8 99 = 7.9 ppm Sr 2+ 0.0079 g Sr 2+ + 10 3 g H 2 O Since the amount of Sr 2+ is so minute compared to the amount of H 2 O we could ignore it in the denominator in part b above and get the same result to 2 sig. fig. .
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28 13.37) A solution contains 14.6 g CH 3 OH in 184 g H 2 O. a) Find mol fraction of CH 3 OH, X CH3OH mol CH 3 OH X CH3OH = ----------------------- (No unit) total mol solution 1 mol CH 3 OH ? mol CH 3 OH = 14.6 g CH 3 OH x --------------------- = 0.45 5 6 mol CH 3 OH 32.04 g CH 3 OH 1 mol H 2 O ? mol H 2 O = 184 g H 2 O x ------------------ = 10. 1 2 mol H 2 O 18.016 g H 2 O 0.45 5 6 mol CH 3 OH X CH3OH = --------------------------------- = 0.042 7 1 = 0.0427 (0.45 5 6 + 10. 1 2) mol soln b) Find mass % CH 3 OH (also called wt % or wt/wt %) mass CH 3 OH mass % CH 3 OH = ------------------------ x 100% total mass solution 14.6 g CH 3 OH mass % CH 3 OH = ------------------------------------- x 100% (14.6 g CH 3 OH + 184 g H 2 O) = 7.3 5 14 % = 7.35 % CH 3 OH c) Find molality of CH 3 OH, m mol CH 3 OH m = ----------------- kg H 2 O 0.45 5 6 mol CH 3 OH m = -------------------------- = 2.4 7 65 = 2.48 m CH 3 OH 0.184 kg H 2 O
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This note was uploaded on 06/11/2011 for the course CHEM 122 taught by Professor Zellmer during the Spring '07 term at Ohio State.

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122ch13c - 27 13.36) a) Note the denominator in mass % is...

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