CH 202 Problem 4.68

(a) How many grams of solute are present in 50.0 mL of 0.488 M K₂Cr₂O₇?

We use the concentration and the volume to get moles, and then convert from moles

to grams using the molar mass:

moles solute:

molar mass of K₂Cr₂O₇ :

grams solute:

(b) If 4.00 g (NH₄)₂SO₄ is dissolved in enough water to form 400 mL of solution, what is the molarity of the solution?

here we calculate M = mol solute/liter solution:

molar mass of solute:

moles solute:

molarity:

(c) How many mL of 0.0250 M CuSO₄ contain 1.75 g of solute?

here, we have a mass and a concentration; convert the mass to moles, and use the concentration and moles to get the volume:

molar mass:

number of moles:

volume = mol/M, so

DAC 7/7/08