What formula do I use to figure. 16.5 g of KCL (MM=74.55 g/mol) is dissolved in enough water to make 575 mL of solution. Calculate the molarity of the KCl solution.
moles = grams/molar mass
Solve for moles.
Then M = mols/L
To calculate the molarity of a solution, you need to use the formula:
Molarity (M) = moles of solute / volume of solution (in liters)
First, you need to convert the given mass of KCl to moles. To do that, use the molar mass of KCl, which is 74.55 g/mol.
moles = mass / molar mass
moles = 16.5 g / 74.55 g/mol
Next, you need to convert the given volume of the solution to liters. The given volume is 575 mL.
volume (in liters) = 575 mL / 1000 mL/L
volume (in liters) = 0.575 L
Now, you have the moles of solute and the volume of the solution in liters. Plug these values into the formula to calculate the molarity.
Molarity (M) = moles of solute / volume of solution (in liters)
Molarity (M) = moles / volume
Molarity (M) = (16.5 g / 74.55 g/mol) / 0.575 L
Calculate the value inside the parentheses first:
Molarity (M) = (0.2212 mol) / 0.575 L
Then, divide the moles by the volume:
Molarity (M) = 0.384 M
So, the molarity of the KCl solution is 0.384 M.