Practice Problems: Solutions (Answer Key)

4/6/2016

Practice Problems: Solutions

Practice Problems: Solutions (Answer Key)

1. What mass of solute is needed to prepare each of the following solutions? a. 1.00 L of 0.125 M K2SO4 21.8 g K2SO4 b. 375 mL of 0.015 M NaF 0.24 g NaF c. 500 mL of 0.350 M C6H12O6 31.5 g C6H12O6

2. Calculate the molarity of each of the following solutions: a. 12.4 g KCl in 289.2 mL solution 0.576 M KCl b. 16.4 g CaCl2 in 0.614 L solution 0.241 M CaCl2 c. 48.0 mL of 6.00 M H2SO4 diluted to 0.250 L 1.15 M H2SO4

3. Calculate the molality of each of the following solutions: a. 2.89 g of NaCl dissolved in 0.159 L of water (density of water is 1.00 g/mL) 0.311 molal NaCl b. 1.80 mol KCl in 16.0 mol of H2O 6.25 molal KCl c. 13.0 g benzene, C6H6 in 17.0 g CCl4 9.80 molal C6H6

4. Calculate the mole fractions of each compound in each of the following solutions: a. 19.4 g of H2SO4 in 0.251 L of H2O (density of water is 1.00 g/mL) H2SO4: 0.0143, H2O: 0.986 b. 35.7 g of KBr in 16.2 g of water KBr: 0.250, H2O: 0.750

c. 233 g of CO2 in 0.409 L of water (density of water is 1.00 g/mL) CO2: 0.189, H2O: 0.811

5. Calculate the mole fraction, molarity and molality 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.

Molarity: 15.8 M NH3, molality: 22.1 molal NH3, mole fraction(NH3): 0.285



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4/6/2016

Practice Problems: Solutions

6. Calculate the molalities of the following aqueous solutions:

a. 0.840 M sugar (C12H22O11) solution (density= 1.12 g/mL) 1.01 molal C12H22O11

b. 4.91 M NaOH solution (density = 1.04 g/mL) 5.82 molal NaOH

c. 0.79 M NaHCO3 solution (density = 1.19 g/mL) 0.703 molal NaHCO3

7. A patient has a cholesterol count of 206 mg/dL. What is the molarity of cholesterol in this patients blood if the molecular mass of cholesterol is 386.64 g/mol? (1 L = 10 dL)

5.33 x 103 M cholesterol

8. 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? 1.33 g/mL

b. What volume (in mL) of this solution is needed to make a 1.00 L solution of a 1.00 M phosphoric acid? 82.0 mL

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