Question

Procaine hydrochloride ( MW = 272.77 g/mol) is used as a local anesthetic. Calculate the molarity of a 4.666 m solution which has a density of 1.1066 g/ml.

Answer 1

Answer:

$\boxed{\text{2.274 mol/L}}$

Explanation:

$b = \dfrac{\text{moles of solute}}{\text{kilograms of solvent}}$

Assume 1 kg water.

1. Moles of P.HCl

Then we have 4.666 mol of P.HCl

2. Mass of P.HCl

n = 4.666 mol × 272.77 g/mol = 1271.1 g

3. Total mass of solution

m = 1000 g + 1271.1 g = 2271.1 g solution

4. Volume of solution

$V = \text{2271.1 g} \times \dfrac{\text{1 mL}}{\text{1.1066 g}} = \text{2052.3 mL} = \text{2.0523 L}$

5. Molar concentration  

$\begin{array}{rcl}c & = & \dfrac{\text{moles of solute}}{\text{litres of solution}}\\\\c & = & \dfrac{\text{4.666 mol}}{\text{2.0523 L}}\\\\ & = & \text{2.274 mol/L}\\\end{array}$

$\text{The molar concentration of the solution is} \boxed{\textbf{2.274 mol/L}}$