20mL ethanol(density=o.789g/mol) is dissolved in sufficient water to produce a 200mL solution. the density of the solution is 0.982g/mL. what is the molarity?
Use density of ethanol to convert mL ethanol to grams. Then mol = grams/molar mass.
Then M = mols/L solution.
Vvjjn
To find the molarity of a solution, we need to determine the number of moles of the solute (ethanol) present in the given solution. The formula for molarity (M) is:
M = (moles of solute) / (volume of solution in liters)
First, let's calculate the mass of ethanol present in the 20 mL solution using its density:
Mass of ethanol = volume of ethanol x density of ethanol
= 20 mL x 0.789 g/mL
= 15.78 g
Next, we need to find the mass of the entire solution. Utilizing the density of the solution given, we can calculate the mass of the solution:
Mass of solution = volume of solution x density of solution
= 200 mL x 0.982 g/mL
= 196.4 g
Now, we can determine the mass of water in the solution by subtracting the mass of ethanol from the total mass:
Mass of water = Mass of solution - Mass of ethanol
= 196.4 g - 15.78 g
= 180.62 g
To convert the mass of ethanol to moles, we need to use its molar mass. The molar mass of ethanol (C2H6O) is the sum of the atomic masses of its constituent elements:
Molar mass of ethanol = 2(Carbon's atomic mass) + 6(Hydrogen's atomic mass) + (Oxygen's atomic mass)
= 2(12.01 g/mol) + 6(1.01 g/mol) + 16.00 g/mol
= 46.07 g/mol
Now, we can calculate the moles of ethanol:
Moles of ethanol = mass of ethanol / molar mass of ethanol
= 15.78 g / 46.07 g/mol
≈ 0.3424 mol
Finally, we can use the molarity formula to calculate the molarity:
Molarity (M) = moles of solute / volume of solution (in liters)
= 0.3424 mol / (200 mL / 1000 mL/L)
= 0.3424 mol / 0.2 L
= 1.712 M
Therefore, the molarity of the solution is approximately 1.712 M.