Question

Concentrated hydrochloric acid is 37.0% HCl by mass and has a density of 1.18 g/mL. What is the molar concentration of concentrated hydrochloric acid?

Answer 1

Let volume of solution be 1 L

volume , V = 1 L

= 1*10^3 mL

density, d = 1.18 g/mL

mass = density * volume

= 1.18 g/mL *1*10^3 mL

= 1180.0 g

This is mass of solution

mass of HCl = 37.0 % of mass of solution

= 37.0*1180.0/100

= 436.6 g

Molar mass of HCl,

MM = 1*MM(H) + 1*MM(Cl)

= 1*1.008 + 1*35.45

= 36.458 g/mol

mass(HCl)= 436.6 g

number of mol of HCl,

n = mass of HCl/molar mass of HCl

=(436.6 g)/(36.458 g/mol)

= 11.98 mol

volume , V = 1 L

Molarity,

M = number of mol / volume in L

= 11.98/1

= 11.98 M

Answer: 12.0 M