Molarity = [tex] \frac{Solute(in Moles)}{Solution (in Liters)} [/tex]
Moles of Caffeine = Mass of Caffeine/Molar Mass
Mass = 100 mg = 0.1 g
Molar Mass = 196 g/mole
Moles of Caffeine in one cup = 0.1/196 moles
= 5.102 * 10^-4 moles
If one cup of coffee is ingested (A typical adult contains about 40 liters of water),
Molarity of caffeine = [(5.1 * 10^-4)/ 40] M
= 0.012755 mM
The toxic molarity of caffeine in the body 10mM
How many cups will be toxic?
= Toxic Molarity/ Molarity of 1 cup
= 10/ 0.012755
= 784
In other words, you would have to drink 784 cups of coffee to reach the dose required to interfere with the DNA replication checkpoint mechanism.