Calculate the molarity of a solution of ethanol in water, in which the mole fraction of ethanol is 0.040 (assume the density of water to be one).

Question

Consider the following species: N^3- , O^2-, F^-, Na⁺, Mg²⁺ and Al³⁺

Answer 1

Given:

Mole fraction of ethanol, X_ethanol = 0.040
Density of water = 1 g mL⁻¹
Molar mass of water = 18 g mol⁻¹

Step 1: Assume volume of solution

Assume 1 L (1000 mL) of solution.

Since density of water is 1 g mL⁻¹,
Mass of water ≈ 1000 g

Step 2: Calculate moles of water

Moles of water = Mass / Molar mass

= 1000 / 18

= 55.56 mol

Step 3: Calculate moles of ethanol

Mole fraction of ethanol:

X_ethanol = n_ethanol / (n_ethanol + n_water)

0.040 = n_ethanol / (n_ethanol + 55.56)

n_ethanol = (0.040 / 0.960) × 55.56

n_ethanol = 2.31 mol

Step 4: Calculate molarity of ethanol

Molarity = Moles of solute / Volume of solution (in L)

Molarity = 2.31 / 1

Molarity = 2.31 M

Final Answer:

The molarity of ethanol in the solution is:
≈ 2.3 M

Solution and Explanation