Question

The density of a 25.0% HCl solution (by mass) is 1.05 g/mL, what is the molality of the solution?
(MW HCI: 36.46g/mol, H2O: 18.015g/mol)
a. 9.60 m
b. 6.86 m
c. 7.20 m
d. 9.14 m
e. None of the above

Answer 1

Answer:

[HCl] = 14.7M in HCl

Explanation:

Definition of Molarity (M) = moles solute / Liters of Solution

Given 25.0% HCl (aq) => 25g HCl/100g Solution => ? moles HCl/Liter Solution

Convert 25g HCl to moles = moles solute

moles HCl => moles HCl = 25g HCl / 18.015g HCl/mole HCl = 1.387732 mole HCl = 1.4 moles HCl (2sig.figs.)

Determine Liters of Solution as follows:

Given 25% HCl Solution => 25g HCl/100 g Solution

100 g Solution = (100 g solution) /  (1.05 g Solution/ml Solution )

= 95.2381 ml Solution x 1 Liter Solution/1000 ml Solution

= 0.0952 Liters Solution

Apply above mole and volume data to definition of mole.

∴Molarity = moles solute / Liters solution

= 1.4 moles solute (HCl)/0.0952 L solution

= 14.7 Molar in HCl(aq)