How many grams of potassium chloride are dissolved to make 5.00 L of a 0.400 M solution? Use molar masses with at least as many significant figures as the data given.
2007-01-10 14:44:50 · 0 answers · asked by Anonymous in Science & Mathematics ➔ Chemistry
Molarity is given as the number of moles of solute per Liters of solution.
Molarity = moles / Liter
Re-arranging the above equation for molarity to solve for moles we get,
moles = Molarity * Liters
You are told the Molarity of the solution in the problem. You are told the volume of the final solution. With these two pieces of data, you can calculate the number of moles of solute needed and from this you can find the number of grams need.
Plugging into the equation,
moles = Molarity * Liters
moles = 0.400 M * 5.00 L = 2.00 moles
To convert moles to grams we need to multiply by the molar mass of the substance.
Potassium Chloride has a molar mass of: 74.55 g/mol.
mass of KCl = moles of KCl * molar mass of KCl
mass of KCl = 2.00 moles * 74.55 g/mol
mass of KCl = 151.1 grams
If we want to continue using 3 significant figures, this would be 151 grams KCl.
2007-01-10 14:55:06 · answer #1 · answered by mrjeffy321 7 · 0⤊ 0⤋