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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: amcavoy on April 27, 2007, 06:38:14 PM

Title: Morphine
Post by: amcavoy on April 27, 2007, 06:38:14 PM

A solution is prepared from 10.0mL of 0.100M cacodylic acid (K_a=6.5x10^-7), and 10.0mL of 0.080M NaOH.  This this, the equivalent of 3.62x10^-7g of solid morphine (a weak base; MW=285.34; K_b=1.6x10^-6) was added.  If we call morphine a base, B, calculate the fraction of morphine present in the protonated form, BH⁺.

The hint to this problem was that there is an easy way and a hard way.  Could someone tell me which method would be considered the easy way and which would be considered the hard way?

Title: Re: Morphine
Post by: Borek on April 27, 2007, 07:05:31 PM

List both methods so that we can decide ;)

Title: Re: Morphine
Post by: Yggdrasil on April 28, 2007, 02:09:06 PM

What will be the pH of the Cacodylic acid/NaOH solution you created?  How many moles of morphine are you adding?  Will that amount of morphine be enough to change the pH (the answer to this question determines whether you are going the hard or easy route)?  Given pH and pKa, how can you calculate the ratio of morphine to its conjugate acid?