You dissolve 17.1 gms of sucrose (sugar) in 100 mL of ethanol 20ºC. What is the molarity (M)?
I don't know. The close answer is
mols sucrose = grams/molar mass
Then M = mols/L SOLUTION. Dissolving the solid in 100 mL ethanol makes the SOLUTION greater than 0.1 L. I'm sure the author of the problem meant for you to ignore the difference and use 0.1 L; however you need to be aware that M is mols/L solution and NOT mols/L.I am especially picky about this point because many students don't realize there is a difference between adding a solute to 1000 mL solvent vs adding solute to enough solvent to make 1000 mL solution.
To find the molarity (M) of a solution, you need to know the moles of solute (sucrose) and the volume of the solution.
First, we need to calculate the moles of sucrose. The molar mass of sucrose (C12H22O11) is:
12 * 12.01 g/mol (carbon) + 22 * 1.01 g/mol (hydrogen) + 11 * 16.00 g/mol (oxygen) = 342.30 g/mol.
To find the moles, we divide the mass of sucrose (17.1 g) by its molar mass (342.30 g/mol):
moles of sucrose = 17.1 g / 342.30 g/mol = 0.05 mol.
Next, we need to calculate the volume of the solution in liters. The given volume is 100 mL, which is equal to 0.1 L.
Finally, we can calculate the molarity by dividing the moles of sucrose by the volume of the solution expressed in liters:
Molarity (M) = moles of sucrose / volume of solution (in liters)
Molarity = 0.05 mol / 0.1 L = 0.5 M.
Therefore, the molarity of the solution is 0.5 M.