Name ______KEY______

Beaker A / Beaker B / Beaker C
6.00 grams of sucrose in the form of sugar cubes is placed in 1.00 L of water at a temperature of 25 ̊C. The solution was stirred continuously with a magnetic stir bar at a speed of 60 rpm. Time was measured with a stop watch from time sugar was placed in water until it visibly disappeared. / 6.00 grams of sucrose in the form of granulated sugar is placed in 1.00 L of water at a temperature of 25 ̊C. The solution was stirred continuously with a magnetic stir bar at a speed of 60 rpm. Time was measured with a stop watch from time sugar was placed in water until it visibly disappeared. / 6.00 grams of sucrose in the form of powdered sugar is placed in 1.00 L of water at a temperature of 25 ̊C. The solution was stirred continuously with a magnetic stir bar at a speed of 60 rpm. Time was measured with a stop watch from time sugar was placed in water until it visibly disappeared.
  1. What hypothesis was being tested in the experiment above? If the surface area of the solute is increased, then the dissolution time will decrease. Or, If the particle size of the solute is decreased, then the dissolution time will decrease.
  2. Sketch a picture of LiCl dissolved in water at the molecular level. Be sure to show the correct orientation of the water molecules around the ions. (Figure 9 on page 411)
  1. What is a solvent? Look it up!
  1. Which solution is more dilute? 0.03 M NaCl or 0.001 M NaCl
  1. Which solution is more concentrated? 50.0 mL of 0.02 M NaCl or 25.0 mL of 0.02 M NaCl They are the same
  1. Describe what is happening at the molecular level in a saturated solution at dynamic equilibrium. (Pg. 408-409)

Read it!

  1. Study table 4 on page 410.
  2. In general, what happens to the solubility of ionic compounds in water as the temperature increases?

increases

  1. What happens to the solubility of gases as the temperature of the water increases?

decreases

  1. Which two ionic compounds shown in the table become less soluble in water as the temperature increases? Li2CO3 and Ce2(SO4)3
  1. Study figure 15 on page 414.
  2. How many grams of RbCl will dissolve in 100 grams of water at 25 ̊C? about 95 g
  3. Make a true general statement about the effect of temperature on the solubility of KNO3 compared to LiCl. Temperature has a greater affect on the solubility of KNO3 compared to LiCl.
  4. Explain why molarity changes with temperature, while molality does not. Because volume changes with temperature, but mass does not.
  1. Write a balanced dissociation equation (dissolving equation) for Na3PO4.

Na3PO4  3 Na+ + PO43-

  1. If 0.003 moles of Na3PO4 are dissolved in 1.00 L of water…
  2. How many moles of PO43- ions are dissolved in the water? 0.003 moles
  3. How many moles of Na+ ions are dissolved in the water? 0.009 moles
  1. If 100.0 mL of 0.2 M ZnCl2 are mixed with 100.0 mL of 0.2 M NaOH…
  2. What is the precipitate? Zn(OH)2
  3. What ions will be in the solution above the precipitate? Na+, Cl-, Zn2+
  4. How many moles of precipitate can be made? 0.01 mol
  5. Which is the limiting reactant? NaOH
  6. How many moles of the excess reactant were not used? 0.01 mol excess ZnCl2
  1. If 50.0 mL of 0.3 M Na2CO3 are reacted with 40.0 mL of 0.4 M Ba(NO3)2 , what is the maximum number of moles of precipitate that can be produced? 0.015 mol BaCO3
  1. A precipitate is filtered and dried and it is discovered that the actual mass of the precipitate is less than the theoretical (calculated) mass. What could explain the difference?
  2. The precipitate wasn’t washed very well with distilled water.
  3. The precipitate didn’t have time to form large crystals so it didn’t all get trapped in the filter.
  4. The precipitate was still hydrated even after drying.
  5. The reaction didn’t go to completion due to incomplete mixing of the reactants.
  1. If 1.000 mole of C12H22O11 is dissolved in 1.000 liter of water, how many solute particles are dissolved in the water? 6.022 X 1023 particles
  2. If 1.000 mole of NaCl is dissolved in 1.000 liter of water, how many solute particles are dissolved in the water? 1.200 X 1024 particles

A student finds a bottle of copper (II) chloride in the stockroom, but the molarity is not labeled. The student pipettes 5.5 ml of the solution into a test tube and adds an excess of aqueous sodium phosphate until it appears that no more precipitate has formed. The student filters and dries the precipitate. The data are shown below.

Mass of filter paper / 1.033 g
Volume of copper (II) chloride added to test tube / 5.5 ml
Mass of filter paper + precipitate / 2.466 g
Mass of precipitate / 1.433 g
  1. What is the molarity of the copper (II) chloride solution? 2.1 M
  1. How would you prepare 50.0 mL of 0.10 M NaCl? (answer in grams and explain how to make it) Dissolve 0.29 grams of NaCl in distilled water and raise the final volume to 50.0 mL