Problem: The "free-base" form of cocaine (C17H21NO4) and its protonated hydrochloride form (C17H22ClNO4) are shown below; the free-base form can be converted to the hydrochloride form with one equivalent of HCl. For clarity, not all the carbon and hydrogen atoms are shown; each vertex represents a carbon atom with the appropriate number of hydrogen atoms so that each carbon makes four bonds to other atoms.The free-base form of cocaine has a solubility of 1.00 g in 6.70 mL ethanol (CH3CH2OH). Calculate the molarity of a saturated solution of the free-base form of cocaine in ethanol.

FREE Expert Solution

We’re being asked to calculate the molarity of a saturated solution of the free-base form of cocaine in ethanol given its solubility.


Recall that molarity is the ratio of the moles of solute and the volume of solution (in liters). In other words:


Molarity=moles soluteL solution


We’re given the solubility of free-base cocaine in ethanol.  Recall that Solubility is the maximum amount of solute that can dissolve in a solvent.


  • This means that only 1.00 g of free-base cocaine will dissolve in 6.70 mL ethanol (CH3CH2OH)
  • A saturated solution contains the maximum amount of solute that can be dissolved in a solvent at a particular temperature. 


The steps we need to do for this solution are:

Step 1: Calculate the moles of free-base cocaine (C17H21NO4

Step 2: Calculate the volume of the solution (in L).

Step 3: Calculate the molarity of the saturated solution.


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Problem Details

The "free-base" form of cocaine (C17H21NO4) and its protonated hydrochloride form (C17H22ClNO4) are shown below; the free-base form can be converted to the hydrochloride form with one equivalent of HCl. For clarity, not all the carbon and hydrogen atoms are shown; each vertex represents a carbon atom with the appropriate number of hydrogen atoms so that each carbon makes four bonds to other atoms.

Cocaine is a seven membered ring with carbon as all of its vertices and both the upper left and lower left vertices single bonded to the same N; that N is single bonded to CH3. The upper right vertex is single bonded to COOCH3, and the right point is single bonded to an O that is single bonded to a CO attached to the lower left vertex of a benzene ring with its points arranged vertically. Cocaine is added to HCl to produce cocaine hydrochloride. Cocaine hydrochloride has the same structure as cocaine, except the N attached to the seven-membered ring is now N+ and is also single bonded to the H from HCl. Cl- is nearby.


The free-base form of cocaine has a solubility of 1.00 g in 6.70 mL ethanol (CH3CH2OH). Calculate the molarity of a saturated solution of the free-base form of cocaine in ethanol.

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