A chemist prepares a solution of mercury(I) chloride Hg2Cl2 by measuring out
0.000126 μmol of mercury(I) chloride into a 100. mL volumetric flask and filling the flask to the mark with water.
Calculate the concentration in mmol/L of the chemist's mercury(I) chloride solution.
Round the answer to three significant figures.

1.26 × 10^-8 M

Explanation:

We are given;

Number of moles of mercury (i) chloride as 0.000126 μmol

Volume is 100 mL

We are required to calculate the concentration of the solution.

We need to know that;

Concentration is also known as molarity is given by;

Molarity = Number of moles ÷ Volume

Number of moles = 1.26 × 10^-10 Moles

Volume = 0.01 L

Therefore;

Concentration = 1.26 × 10^-10 Moles ÷ 0.01 L

                       = 1.26 × 10^-8 M

Thus, the molarity of the solution is 1.26 × 10^-8 M

the formula mass of a molecule or a compound is the sum of the atomic weights of the atoms in its empirical formula

(that's what i know about formula mass)