Amphetamine(C9H13N) is a weak base with a pKb of 4.2.?

Calculate the pH of a solution containing an amphetamine concentration of 240 mg/L.

4 Answers

  • Moles = 0.240 g / 135 g/mol=0.00178

    initial concentration = 0.00178 M

    Kb = 10^-6.3 x 10^-5 = x^2 / 0.00178-x

    x = [OH-]= 0.000335 M

    pOH = 3.47

    pH = 14 – pOH = 10.5

  • Base Amphetamine

  • I don’t understand where they got 10^-6.3 and 10^-5. I thought it would be 10^-4.2 but that’s not right.

  • Why do you find Kb by using 10^-(Kb)? shouldnt it be 10^-(pKb)?

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