Name: ______Date: ______

Practice Exam Unit 6

Terms:

  1. Saturated solution = solution holds maximum amount of solute for a given amount to solvent.
  2. Solubility = solvent’s ability to dissolve a solute.
  3. Unsaturated solution = a solvent does not contain the maximum amount of solute.
  4. Miscible = two or more liquids dissolve in one another.
  5. Immiscible = two or more liquids do not dissolve in one another.
  6. Supersaturated solution
  7. Molarity
  8. Percent solutions – (volume/volume) and (mass/volume)
  9. Molality
  10. Mole Fraction

Practice Problems:

  1. Show how each of the following strong electrolytes “breaks up” into its component ions upon dissolving in water.
  2. NaBr à Na+ + Br-
  3. MgCl2 à Mg2+ + 2 Cl-
  4. Al(NO3)3à Al3+ + 3 NO3-
  5. (NH4)2SO4 à 2 NH4+ + SO42-
  6. HI à H+ + I-
  1. Describe how you would prepare 1.0 L of each of the following solutions
  2. 0.10 M NaCl from solid NaCl

Place 5.9 grams into a 1.0mL volumetric flask that is ½ filled with water. Mix until dissolved. Dilute to line with water. Mix.

  1. 0.10 M NaCl from a 2.5 M stock solution

Add 40. mL of 2.5M stock solution using a volumetric pipette. Add to a 1.0 l volumetric flask. Dilute with water to the line. Mix

  1. 0.20 M NaIO3 from solid NaIO3

Add 40. g of NaIO3 to a 1.0L volumetric flask ½ filled with water. Mix to dissolve. Add water to the line. Mix.

  1. Calculate the molarity of each of these solutions:
  2. A 5.263-g sample of NaHCO3 is dissolved in enough water to make 250.0 mL of solution.

0.252 M

  1. A 184.6-mg sample of K2Cr2O7 is dissolved in enough water to make 500.0 mL of solution.

1.247 x10-3 M

  1. A solution is prepared by mixing 1.00 g ethanol (C2H5OH) with 100 g water to give a final volume of 101 mL. Calculate the molarity, mole fraction and molality of ethanol in this solution.

Molarity = 0.215M

Mole Fraction for ethanol = 0.00389

molality = 0.217 molal

  1. Place the following solutions in order from strongest to weakest electrolyte.
  2. 1.0 M glucose in water
  3. 1.0 M HCl in water
  4. 1.0 M MgCl2 in water
  5. pure water

strongest à weakest

c > b > a > d

The more ions in solution the stronger the electrolyte. Since MgCl2 will produce 3 ions, it is the strongest. HCl will produce 2 ions, glucose will not ionize because it is a molecular compound and pure water has no ions or dissolved molecules in it.

  1. Mercury and its compounds have many uses, from filling teeth (as an alloy with silver, copper and tin) to the industrial production of chlorine. Because of their toxicity, however, soluble mercury compounds, such as mercury(II) nitrate must be removed from industrial wastewater. One removal method reacts the wastewater with sodium sulfide solution to produce solid mercury(II) sulfide and sodium nitrate solution. In a laboratory simulation, 0.050 L of 0.010M mercury nitrate reacts with 0.020L of 0.010 M sodium sulfide.
  2. Write the balanced equation.

Hg(NO3)2 (aq) + Na2S(aq) à HgS(s) + 2 NaNO3 (aq)

  1. How many grams of the mercury(II) sulfide is formed?

Limit = Na2S 0.047 g HgS Produced

  1. How would you make up a 3.00 L solution of 0.982M solution of mercury(II) sulfide? You can use some other solvent to make sure it goes into solution. Give a complete description.

Weigh out 685 g of HgS, place into a 3.00 L volumetric flask that is ½ filled with water. Agitate until completely dissolved. Fill to the line with water. Mix the solution.

  1. What volume of the solution would you need to obtain 0.125 moles of mercury(II) ions?

0.127 L

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