Caffeine (c8h10n4o2) is a weak base with a pkb of 10.4. part a calculate the ph of a solution containing a caffeine concentration of 430 mg/l.

Concentration of caffeine is 430 mg/L = 0.43g/L

The molar mass of caffeine is 194.19 g/mol

Therefore the molarity is:

Molarity = (0.43/194.19) mol/L

Molarity = 0.002214 mol/L

Molarity = 0.002214 M

Given pKb = 10.4:

Kb = 10^-pKb = 10^ - 10.4 = 3.981 x 10^ - 11

Kb is equivalent to:

Kb = [caffeine H+][OH-] / [caffeine]

3.981 x 10^ - 11 = [caffeine H+][OH-] / (0.002214)

[caffeineH+][OH-] = 8.815 x 10^ - 14

But since:

[caffeineH+] = [OH-]

Hence,

[OH-]^2 = 8.815 x 10^ - 14

[OH-] = 2.969 x 10^ - 7

The formula for pH is:

pH = 14 + log [OH-]

pH = 7.47