Question

The hydrochloride form of cocaine has a solubility of 1.00 g in 0.400 mL water. Calculate the molarity of a saturated solution of the hydrochloride form of cocaine in water.Express your answer to three significant figures and include the appropriate units.

Answer 1

The molarity of the solution is 7.4 mol/L

Step-by-step explanation:

From the question above

0.400 ml of water contains 1.00 g of hydrochloride form of cocaine

Therefore 1000 ml of water will contain x g of hydrochloride form of cocaine

x = 1000 / 0.400

x = 2500 g

2500g of hydrochloride form of cocaine is present in 1000 ml of water.

Mole of hydrochloride form of cocaine = mass /molar mass of hydrochloride

Mole of hydrochloride form of cocaine = 2500/339.8

= 7.4 mol

Molarity = mol/ volume in liter (L)

molarity = 7.4 /1

Molarity = 7.4 mol/L

Answer 2

`M=7.35M`

Step-by-step explanation:

Hello,

In this case, the cocaine hydrochloride whose molecular formula is:

`C_(17)H_(22)ClNO_4`

Has a molar mass of 339.8 g/mol, for that reason, in 1.00 g there are the following moles:

`n=1.00gC_(17)H_(22)ClNO_4*(1molC_(17)H_(22)ClNO_4)/(339.8gC_(17)H_(22)ClNO_4) =2.94x10^(-3)molC_(17)H_(22)ClNO_4`

Such calculations are performed at the saturation condition with which the molarity is obtained as:

`M=(n)/(V)`

Thus, the volume in liters is:

`V=0.4mL*(1L)/(1000mL) =4x10^(-4)L`

As we assume the volume does not change when the cocaine hydrochloride is added to the water, therefore, we obtain the molarity:

`M=(2.94x10^(-3)molC_(17)H_(22)ClNO_4)/(4.00x10^(-4)L) =7.35M`

Best regards.