Answer :
The molality of the solution is approximately 1.55 m. Therefore, the correct answer is A) 1.55 m.
To find the molality (m) of the solution, we need to determine the number of moles of the solute (propyl alcohol) and the mass of the solvent (water).
Given:
Mass of propyl alcohol (solute) = 35.0 g
Mass of water (solvent) = 200 g
Step 1: Convert the mass of propyl alcohol to moles.
First, we need to calculate the molar mass of propyl alcohol (C3H7OH):
C = 12.01 g/mol, H = 1.008 g/mol, O = 16.00 g/mol
Molar mass of propyl alcohol = (3 * 12.01 g/mol) + (8 * 1.008 g/mol) + 16.00 g/mol = 60.12 g/mol
Now, we can calculate the number of moles of propyl alcohol:
Number of moles of propyl alcohol = Mass of propyl alcohol / Molar mass of propyl alcohol
= 35.0 g / 60.12 g/mol
Step 2: Calculate the molality.
Molality (m) is defined as the number of moles of solute per kilogram of solvent.
Mass of water (in kg) = Mass of water (g) / 1000
Now we can calculate the molality:
Molality (m) = Number of moles of propyl alcohol / Mass of water (in kg)
= (35.0 g / 60.12 g/mol) / (200 g / 1000)
Simplifying the expression, we get:
Molality (m) = (35.0 g * 1000) / (60.12 g/mol * 200 g)
= 1.55 m (rounded to two decimal places)
Option A
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