# Solutions and Density Problems ```The dehydrated form of Epsom salts is magnesium sulfate (MgSO4).
a) What is the percent magnesium sulfate by mass in a solution made from 16.0 g MgSO4 and 100 mL of
H2O? The density of water is .997 g/mL.
b) Calculate the molarity of the solution.
2. Concentrated hydrochloric acid (HCl) is 36.5% HCl by mass. Its density is 1.18 g/mL. Calculate the
molarity of HCl.
3. Phosphoric acid is usually obtained as an 87.0% phosphoric acid solution. If it is 13.0 M, what is the
density of this solution?
4. Concentrated hydrochloric acid is usually available at a concentration of 37.7% by mass. What is its
molar concentration? (The density of the solution is 1.19 g/mL.)
5. I have a bottle of NH3. Its strength is 32.0% and its density is 0.89 g/mL. Determine the molarity.
6. The density of toluene (C7H8) is 0.867 g/mL, and the density of thiophene (C4H4S) is 1.065 g/mL. A
solution is made by dissolving 9.660 g of thiophene in 260.0 mL of toluene. Assuming that the volumes of
the solute and solvent are additive, determine the molarity of thiophene in the solution.
7. The density of an aqueous solution of nitric acid is 1.430 g/mL. If this solution contained 36.00% nitric
acid by mass, how many mL of the solution would be needed to supply 150.20 grams of nitric acid?
8. Calculate the molarity of NH3 if it is in a solution composed of 30.6 g NH3 in 81.3 g of H2O. The density
of the solution is 0.982 g/mL and the density of water is 1.00 g/mL.
9. A patient has a cholesterol count of 206 mg/dL. What is the molarity of cholesterol in this patient’s
blood if the molecular mass of cholesterol is 386.64 g/mol?
10. Concentrated phosphoric acid is 90% H3PO4 by mass and the remaining mass is water. The molarity of
H3PO4 in 90% H3PO4 is 12.2 M at room temperature.
a) What is the density of this solution at room temperature?
b) What volume (in mL) of this solution is needed to make a 1.00 L solution of a 1.00 M phosphoric acid?
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