4.1.3 Solubility of Group 2 Compounds

• What is the definition of solubility?

  Maximum substance dissolved in solvent
• Solubility is expressed in units like grams per 100 cm³ or moles per liter
• Polar solutes dissolve better in polar solvents.
• How does temperature affect the solubility of most solids in liquids?

  Solubility increases
• The solubility of gases increases with pressure.
• The presence of a common ion decreases the solubility
• Arrange the Group 2 hydroxides in order of increasing solubility in water:

  1️⃣ Magnesium hydroxide (Mg(OH)₂)

  2️⃣ Calcium hydroxide (Ca(OH)₂)

  3️⃣ Strontium hydroxide (Sr(OH)₂)

  4️⃣ Barium hydroxide (Ba(OH)₂)
• What two enthalpy changes determine the solubility of ionic compounds?

  Lattice and hydration enthalpy
• Larger cations in Group 2 hydroxides have stronger electrostatic attractions to OH⁻ ions.

  False
• As the cation size in Group 2 increases, both lattice enthalpy and hydration enthalpy decrease
• Which type of solvent do non-polar solutes dissolve in?

  Non-polar solvents
• Solubility of solids in liquids increases with temperature.
• The solubility of gases increases with pressure
• What effect does the presence of a common ion have on salt solubility?

  Decreases it
• Match the factor affecting solubility with its effect:

  Polarity ↔️ Polar solutes in polar solvents

  Temperature ↔️ Increases for solids, decreases for gases

  Pressure ↔️ Increases for gases
• The solubility of Group 2 hydroxides increases down the group.
• As the cation size increases in Group 2 hydroxides, the lattice enthalpy decreases more significantly than the hydration
• Arrange Group 2 hydroxides in order of increasing solubility in water:

  1️⃣ Magnesium hydroxide (Mg(OH)₂)

  2️⃣ Calcium hydroxide (Ca(OH)₂)

  3️⃣ Strontium hydroxide (Sr(OH)₂)

  4️⃣ Barium hydroxide (Ba(OH)₂)
• What is the general solubility trend of Group 2 sulfates down the group?

  Decreases
• The decrease in hydration enthalpy is more significant than the decrease in lattice enthalpy for Group 2 sulfates.
• Match the Group 2 sulfate with its solubility in water at 25°C (g/100 mL):

  Magnesium sulfate (MgSO₄) ↔️ 26.9

  Calcium sulfate (CaSO₄) ↔️ 0.209

  Strontium sulfate (SrSO₄) ↔️ 0.0113

  Barium sulfate (BaSO₄) ↔️ 0.00025
• Which Group 2 compounds are used as antacids to neutralize stomach acid?

  Magnesium hydroxide and calcium carbonate
• Barium sulfate is used as a contrast agent in X-ray imaging due to its insolubility.
• Calcium hydroxide is used in agriculture to condition acidic soils by increasing their pH.
• In which industry is magnesium hydroxide used due to its low solubility?

  Wastewater treatment
• Why is barium sulfate used as a filler in plastics and paints?

  Chemical inertness
• Match the Group 2 compound with its application and reason for solubility:

  Magnesium hydroxide (Mg(OH)₂) ↔️ Antacid, neutralizes stomach acid

  Barium sulfate (BaSO₄) ↔️ Contrast agent, insoluble enhances X-ray images

  Calcium hydroxide (Ca(OH)₂) ↔️ Soil conditioner, increases soil pH
• What is the definition of solubility?

  Maximum amount of substance that dissolves
• Polar solutes dissolve in polar solvents
• Sugar dissolves better in hot water than in cold water due to higher solubility at higher temperatures.
• What is the effect of adding sodium chloride (NaCl) to a solution of silver chloride (AgCl)?

  Decreases AgCl solubility
• What effect does adding sodium chloride (NaCl) to a solution of silver chloride (AgCl) have on the solubility of AgCl?

  Decreases solubility
• Polar solutes dissolve in polar solvents
• Solubility increases with temperature for gases but decreases for solids.

  False
• The common ion effect decreases salt solubility
• Why does table salt (NaCl) dissolve well in water but not in oil?

  Polarity
• The solubility of gases increases with pressure.
• What happens to the solubility of Group 2 hydroxides as you move down the group?

  Increases
• The solubility trend of Group 2 hydroxides is governed by changes in lattice enthalpy and hydration enthalpy
• The decrease in lattice enthalpy is more significant than the decrease in hydration enthalpy as you move down Group 2.