Calculate the molarity of caffeine in a 12 oz cola drink containing 28.7 mg of caffeine, C8H10N4O2. (1oz = 29.6 mL)
2007-10-04 15:08:59 · 2 answers · asked by Anonymous in Science & Mathematics ➔ Chemistry
M=mol/liter
28.7mg caffeine/12 oz cola
12 oz cola * 29.6ml/oz *1L/1000ml = 0.3552L
MM caffeine= 194.2g
28.7mg caffeine * 1g/1000mg = 0.0287g
mol = mass/molar mass = .0287/194.2= 1.48*10^-4
1.48*10^-4mol/0.3552L = 4.16 * 10^ -4 M
2007-10-04 15:24:41 · answer #1 · answered by Avi R 2 · 0⤊ 0⤋
To do this you need to calculate the volume of the drink in liters and know what portion of a mole of caffeine is dissolved.
Volume of drink: 12 oz x 29.6ml/oz x 1 liter/1000ml = 0.355 l
MW of caffeine = (8 x 12) + (10 x 1) + (4 x 14) + (2 x 16) = 194g/mole
moles of caffeine in drink:
(28.7mg x 1g/1000mg)/194g/mol = 0.000148 moles
Molarity = 0.000148mol/0.355 L = 0.000417 M
2007-10-04 15:21:36 · answer #2 · answered by Flying Dragon 7 · 0⤊ 0⤋