Caffeine (C8H10N4O2) is a stimulant found in coffee and tea. If a solution of caffeine in the solvent chloroform (CHCl3) has a concentration of 0.0500m, calculate
a)The percentage of caffeine by mass
b)the mole fraction of caffeine in the solution
1 Answer
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Supposing you really mean “m” and not “M”:
“0.0500m” means that 0.0500 mole of C8H10N4O2 was dissolved in 1.000 kg of CHCl3.
a)
(0.0500 mol C8H10N4O2) x (194.1906 g C8H10N4O2/mol) = 9.7095 g C8H10N4O2
(9.7095 g C8H10N4O2) / (9.7095 g + 1000 g) = 0.00962 = 0.962% C8H10N4O2 by mass
b)
(1000 g CHCl3) / (119.3776 g CHCl3/mol) = 8.3768 mol CHCl3
(0.0500 mol C8H10N4O2) / (0.0500 mol + 8.3768 mol) = 0.00593 [the mole fraction of C8H10N4O2]
