Question

calculate the molarity and molality of concentrated of hydrochloric acid. The specific gravity of this solution is 1.19 and its weight percent is solution is 36.5%

Answer 1

consider 100 grams of solution

we know that

% mass = mass of HCL x 100 / mass of solution

so

36.5 = mass of HCl x 100 / 100

mass of HCl = 36.5 g

now

moles = mass / molar mass

so

moles of HCl = 36.5 / 36.5

moles of HCl = 1

now

given

specific gravity = 1.19

so

density of solution / density of water = 1.19

we know that

density of water = 1 g / ml

so

density of solution = 1.19 g / ml

now

volume of solution = mass / density

so

volume of solution = 100 / 1.19

volume of solution = 84.0336 ml

now

we know that

molarity = moles of HCl x 1000 / volume (ml)

so

molarity = 1 x 1000 / 84.0336

molarity = 11.9

so

the molarity is 11.9 M

2)

now

mass of solution = 100

mass of HCl = 36.5

so

mass of solvent = 100-36.5

mass of sovlent = 63.5

now

molality = moles of hCl x 1000 / mass of sovlent (g)

so

molality = 1 x 1000 / 63.5

molality = 15.75

so

the molality of the solution is 15.75 m