What is the molarity of 100 ml of ethanol dissolved in 1.5 liters of water? Ethanol has a specific gravity of 0.789, and its molecular weight is 46 g/mol.
Use density to calculate mass ethanol.
moles = grams/molar mass
Then use M = moles/L soln
To find the molarity of a solution, we need to know the amount of solute (in moles) and the volume of the solution (in liters).
First, let's find the amount of ethanol in moles. We can use the mass of ethanol and its molecular weight to calculate this.
Given that the specific gravity of ethanol is 0.789, we can infer that the density of ethanol is 0.789 g/mL. Therefore, the mass of ethanol in 100 mL of the solution is:
Mass of ethanol = volume of ethanol * density of ethanol
Mass of ethanol = 100 mL * 0.789 g/mL
Mass of ethanol = 78.9 g
Next, let's convert the mass of ethanol to moles. Using the molecular weight of ethanol (46 g/mol), we can calculate the number of moles:
Number of moles of ethanol = Mass of ethanol / Molecular weight of ethanol
Number of moles of ethanol = 78.9 g / 46 g/mol
Number of moles of ethanol ≈ 1.715 moles
Now, let's calculate the total volume of the solution by adding the volume of water (1.5 liters) to the volume of ethanol (100 mL). However, since the units of volume should be consistent, let's convert the 100 mL of ethanol to liters:
Volume of ethanol = 100 mL * (1 L / 1000 mL)
Volume of ethanol = 0.1 L
Total volume of solution = Volume of ethanol + Volume of water
Total volume of solution = 0.1 L + 1.5 L
Total volume of solution = 1.6 L
Finally, we can calculate the molarity of the solution:
Molarity = Number of moles of solute / Volume of solution
Molarity = 1.715 moles / 1.6 L
Molarity ≈ 1.0725 mol/L
Therefore, the molarity of the solution containing 100 mL of ethanol dissolved in 1.5 liters of water is approximately 1.0725 mol/L.