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CHM1045C Test 2 Version 2 answers

# CHM1045C Test 2 Version 2 answers - Name.Recitation Section...

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Name………………………………………..Recitation Section # …………………… CHM1045C Test 2 9 th October 2006 45 Minutes 1 A mole is approximately 6 x 10 23 particles. a How is it defined? Mole is # of atoms in 12g of C-12 2 b By which equation are moles and formula mass (M) related? 2 Number of moles = mass (g) / formula mass, M 2 The molecular formula of glycerol acid is C 3 H 8 O 3. Calculate:- (C = 12, H = 1, O = 16) a The mass of 45.0 millimoles of glycerol 3 1 mole = 92g so 45.0mmoles Mass = (45.0/1000)mol x 92g/mol = 4.14g b The number of molecules of glycerol 2 45mmoles = 0.045mol x 6 x 10 23 particles/mol = 2.70 x 10 22 molecules c The % mass of carbon in glycerol 3 % mass = mass of C / total mass = (3 x 12 ) g/ 92g/mol x 100 = 39% 3 In this reaction, Al 2 (SO 4 ) 3 + 3 Ba (OH) 2 = 2 Al(OH) 3 + 3 BaSO 4 5.2g of aluminum sulfate is completely reacted with barium hydroxide. Calculate:-

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(Al = 27, S = 32, O =16, Ba = 56, H = 1) a The number of moles of aluminum sulfate Moles = mass/ M = 5.2g / (2 x 27 + 3( 32 + 4 x 16))g/mol = 5.2/342mol = 1.5 x 10 -2 or 0.015mol 3 …continued over b
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