Question

A chemist prepares a solution of mercury(II) iodide (HgI,) by measuring out 2.2 mg of mercury(II) iodide into a 500. mL volumetric flask and filling the flask to the mark with water. Calculate the concentration in mol/L of the chemist's mercury(II) iodide solution. Be sure your answer has the correct number of significant digits. mol/L X 5 ?

Answer 1

Molar mass of HgI2,

MM = 1*MM(Hg) + 2*MM(I)

= 1*200.6 + 2*126.9

= 454.4 g/mol

mass(HgI2)= 2.2 mg

= 0.0022 g

use:

number of mol of HgI2,

n = mass of HgI2/molar mass of HgI2

=(2.2*10^-3 g)/(4.544*10^2 g/mol)

= 4.842*10^-6 mol

volume , V = 5*10^2 mL

= 0.5 L

use:

Molarity,

M = number of mol / volume in L

= 4.842*10^-6/0.5

= 9.683*10^-6 molL

Answer: 9.7*10^-6 mol/L