Solubility Concepts and Experiments
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Which factor does NOT significantly influence the solubility of solid substances in a liquid?

  • Inter-particle forces
  • Pressure (correct)
  • Temperature
  • The type of solvent

    • How does the solubility of most solid substances change as temperature increases?

  • Solubility decreases
  • Solubility is unpredictable
  • Solubility generally increases (correct)
  • Solubility remains constant

    • At approximately what temperature is the solubility of sodium sulfate ($Na_2SO_4$) at its maximum value according to the text?

  • 32.4°C (correct)
  • 0°C
  • 100°C
  • 25°C

    • What happens to the solubility of gases in liquids as the temperature increases?

    <p>Solubility decreases</p> Signup and view all the answers

    In the experiment for determining the solubility of NaCl, what is the purpose of adding sodium chloride to water until undissolved salt remains?

    <p>To create a saturated solution</p> Signup and view all the answers

    During the NaCl solubility experiment, what is assumed when transferring 50 mL of the saturated solution to the evaporating dish?

    <p>That the volume of the solution equals the volume of the solvent.</p> Signup and view all the answers

    In experiment 2.3, after evaporation, the mass of the dry sodium chloride is determined. What does the mass represent?

    <p>The mass of the salt that was soluble in the original solution</p> Signup and view all the answers

    Which statement is correct regarding the solubility of NaCl?

    <p>The solubility of NaCl is 36 g/100 mL of water at 25°C and 39 g/100 mL at 100°C</p> Signup and view all the answers

    What is the molality of a solution formed by dissolving 32.0 g of $CaCl_2$ in 271 g of water?

    <p>1.06 m</p> Signup and view all the answers

    How many gram equivalents are present in 49 g of $H_2SO_4$?

    <p>1 eq</p> Signup and view all the answers

    What is the number of equivalents in 0.25 mol of $H_3PO_4$ when it is completely neutralized to $PO_4^{3-}$?

    <p>0.75 eq</p> Signup and view all the answers

    What is the normality of a solution containing 0.75 equivalents of solute in 250 mL of solution?

    <p>3 N</p> Signup and view all the answers

    What mass of $Na_2CO_3$ is required to prepare 200 mL of a 0.2 N solution?

    <p>2.12 g</p> Signup and view all the answers

    A 0.8 M solution of $H_3PO_4$ is prepared. Assuming complete dissociation, what is the normality of this solution?

    <p>2.4 N</p> Signup and view all the answers

    If 1 L of a solution contains 4 equivalents of solute, what is its normality?

    <p>4 N</p> Signup and view all the answers

    What is the 'z' value for $Al_2(SO_4)_3$ in a precipitation reaction?

    <p>6</p> Signup and view all the answers

    If 0.2 moles of $H_3PO_4$ is converted to $H_2PO_4^-$, how many equivalents are present?

    <p>0.2 eq</p> Signup and view all the answers

    A solution has a normality of 0.48 N and contains $Al_2(SO_4)_3$. If the volume is 250 mL, what is the mass of $Al_2(SO_4)_3$?

    <p>6.84 g</p> Signup and view all the answers

    Why are gas molecules in the gaseous state far apart?

    <p>There are negligible attractive intermolecular interactions.</p> Signup and view all the answers

    What effect does increasing external heat have on the solubility of a gas in a liquid?

    <p>It decreases the solubility of the gas.</p> Signup and view all the answers

    According to Henry’s Law, if the partial pressure of a gas above a solution increases, what happens to the solubility of the gas?

    <p>The solubility increases.</p> Signup and view all the answers

    What is the unit of the Henry's law constant (k) when concentration is measured in molarity (M) and pressure in atmospheres (atm)?

    <p>M/atm</p> Signup and view all the answers

    Which of the following best describes the relationship in the equation $C_1/P_1 = C_2/P_2$?

    <p>Directly proportional at constant temperature.</p> Signup and view all the answers

    Which gases do not generally follow Henry's law?

    <p>Gases that form strong hydrogen bonds with water.</p> Signup and view all the answers

    A carbonated beverage is bottled under pressure. What happens when the bottle's cap is removed?

    <p>The solubility of the gas decreases, causing fizzing</p> Signup and view all the answers

    If the solubility of nitrogen gas is $6.8 \times 10^{-4}$ mol/L at 1 atm, what would be its concentration at a partial pressure of 0.78 atm at the same temperature?

    <p>$5.3 \times 10^{-4}$ mol/L</p> Signup and view all the answers

    A solution of carbon dioxide ($CO_2$) has a concentration of 0.032 M at 3.0 atm. If the pressure is increased to 5.0 atm at the same temperature, what is the new concentration of $CO_2$?

    <p>0.053 M</p> Signup and view all the answers

    According to Henry's Law, what happens to the concentration of a dissolved gas if the pressure above it is doubled?

    <p>The concentration will double.</p> Signup and view all the answers

    Why does the solubility of solids or liquids in liquid solvents not change significantly with pressure?

    <p>Because they are incompressible.</p> Signup and view all the answers

    What does the term 'molarity' represent?

    <p>The number of moles of the solute per liter of solution.</p> Signup and view all the answers

    What must be determined experimentally for each combination of gas, solvent, and temperature when applying Henry’s law?

    <p>The Henry’s law constant (k).</p> Signup and view all the answers

    If the temperature of a gas-liquid solution increases, what initially happens to the solubility of the gas?

    <p>It decreases</p> Signup and view all the answers

    Which of the following actions will not increase the solubility of a gas in a liquid?

    <p>Increasing the surface of gas to the liquid.</p> Signup and view all the answers

    What is the mass percentage of a solution prepared by dissolving 25 g of salt in 225 g of water?

    <p>10%</p> Signup and view all the answers

    A solution is made by mixing 40 mL of ethanol with 160 mL of water. What is the volume percent of ethanol in the solution?

    <p>20%</p> Signup and view all the answers

    If a solution contains 5 mg of a pollutant in 2 kg of water, what is the concentration of the pollutant in ppm?

    <p>2.5 ppm</p> Signup and view all the answers

    A solution has a concentration of 8 ppm. If the solution is aqueous, what does this concentration mean in mg/L?

    <p>8 mg/L</p> Signup and view all the answers

    What does a 75% (v/v) solution of glycerol in water mean?

    <p>75 mL of glycerol in 100 mL of solution</p> Signup and view all the answers

    A solution of sodium chloride (NaCl) in water is prepared. The mole fraction of NaCl is 0.30. What is the mole fraction of water?

    <p>0.70</p> Signup and view all the answers

    What is the mass per cent of a solution if 15.0 g of a solute is dissolved in 135 g of water?

    <p>10%</p> Signup and view all the answers

    A 100 mL solution contains 5 g of solute. What is the concentration in % (w/v)?

    <p>5%</p> Signup and view all the answers

    If a water sample contains 3.0 ppb of a contaminant, what does this mean in terms of mass ratio?

    <p>3 g of contaminant per 1,000,000,000 g of solution</p> Signup and view all the answers

    What is the volume percent of a solution if 30 mL of a solute is diluted with 120 mL of solvent?

    <p>20%</p> Signup and view all the answers

    How would you make a 25% (w/w) solution using 50 grams of a solute?

    <p>Dissolve the solute in 150 grams of solvent.</p> Signup and view all the answers

    If a solution contains 50 ppm of a metal ion, and the solution's volume is 2 liters, approximately how many mg of the metal ion are present?

    <p>100 mg</p> Signup and view all the answers

    A solution is made by dissolving 12g of solid in water to make 300 mL of final volume. What is the % (w/v) of the solution?

    <p>4%</p> Signup and view all the answers

    Which scenario requires the use of parts per million (ppm) or parts per billion (ppb)?

    <p>Measuring the concentration of trace pollutants in water.</p> Signup and view all the answers

    If a solution contains 0.05 moles of solute and 0.45 moles of solvent, what is the mole fraction of the solute?

    <p>0.10</p> Signup and view all the answers

    A solution contains 0.25 moles of solute and 2.5 moles of solvent. What is the mole fraction of the solute?

    <p>0.091</p> Signup and view all the answers

    What is the mole percent of a solution containing 1 mole of solute and 3 moles of solvent?

    <p>25%</p> Signup and view all the answers

    If 8 grams of a solute with a molar mass of 40 g/mol is dissolved in enough solvent to make 200 mL of solution, what is the molarity of the solution?

    <p>1.0 M</p> Signup and view all the answers

    Which of the following is NOT a drawback of using molarity as a measure of concentration in precise work?

    <p>Molarity is expressed in terms of moles instead of mass</p> Signup and view all the answers

    How many moles of NaCl are needed to prepare 500 mL of a 0.25 M solution?

    <p>0.125 mol</p> Signup and view all the answers

    Which concentration unit is defined as the number of moles of solute per kilogram of solvent?

    <p>Molality</p> Signup and view all the answers

    What is the molality of a solution prepared by dissolving 18 g of glucose (C6H12O6) in 200 g of water? (Molar mass of glucose = 180 g/mol)

    <p>0.5 m</p> Signup and view all the answers

    Which of the following remains constant with changes in temperature?

    <p>Molality</p> Signup and view all the answers

    What information is required to calculate the normality of a solution?

    <p>Mass of the solute, equivalent weight of the solute, and volume of the solution</p> Signup and view all the answers

    If a solution has a normality of 2 N, how many gram equivalents of solute are present in 500 mL of the solution?

    <p>1.0</p> Signup and view all the answers

    What does 'z' represent in the formula: equivalent weight = molar mass / z

    <p>Number of replaceable hydrogen ions or hydroxide ions per molecule</p> Signup and view all the answers

    To prepare 1 liter of a 0.5 M solution of a substance with a molar mass of 100 g/mol, how many grams of the substance are required?

    <p>50 g</p> Signup and view all the answers

    A 300 g solution contains 30 g of solute, what is the mass percent of the solute?

    <p>10%</p> Signup and view all the answers

    Which of the following concentration units is most affected by changes in temperature?

    <p>Molarity</p> Signup and view all the answers

    If 20g of a substance with a molar mass of 50g/mol is dissolved in 500g of solvent, what is the molality of the solution? (in mol/kg)

    <p>0.8 m</p> Signup and view all the answers

    Study Notes

    Factors Affecting Solubility

    • Solubility of a substance in a solvent is influenced by inter-particle forces, temperature, and pressure (for gases only).
    • Solid solutes generally increase in solubility with temperature. Sodium sulfate solubility increases significantly between 0°C and 32.4°C.
    • For example, NaCl solubility is 36 g/100 mL of water at 25°C and 39 g/100 mL at 100°C.
    • Gases decrease in solubility with increasing temperature. Heat breaks attractive forces between gas and solvent molecules.

    Experiment: Determining Solubility of NaCl

    • Objective: Determine the solubility of NaCl.
    • Apparatus: Beaker, evaporating dish, measuring cylinder, glass rod, filter paper, analytical balance, Bunsen burner.
    • Chemicals: Sodium chloride and water.
    • Procedure:
      • Weigh an empty evaporating dish.
      • Add 100 mL water to a beaker and 20g of NaCl.
      • Stir vigorously until no more NaCl dissolves, leaving undissolved solute at the bottom.
      • Take 50 mL of the saturated solution.
      • Evaporate the solution in an evaporating dish until dry.
      • Cool the evaporating dish and re-weigh.
      • Calculate solubility in grams of NaCl/100 g of water. Repeat with sugar.

    Effect of Pressure on Gas Solubility (Henry's Law)

    • Pressure greatly affects the solubility of gases. Solids and liquids are not significantly affected by pressure.

    • Solubility of gases increases as the partial pressure of the gas above the solution increases.

    • Henry's Law: C ∝ P or C = kP Where:

      • C is the concentration of dissolved gas at equilibrium.
      • P is the partial pressure of the gas.
      • k is the Henry's law constant (dependent on the specific gas, solvent, and temperature).

    • The constant, k, is experimentally determined and used to calculate solubility.

    • If partial pressure changes while temperature stays constant, then solubility changes proportionately: C1/P1 = C2/P2

    • Gases with stronger intermolecular forces (like hydrogen bonding) or that react with water do not follow Henry's Law.

    Examples of Henry's Law

    • Example 1: CO2 in cola

      • Partial pressure of CO2 inside bottle = 4 atm.
      • Henry's law constant for CO2 in water = 3.3 x 10⁻² mol/L.atm.
      • Calculate CO2 solubility = 0.132 mol/L

    • Example 2: N2 solubility in water

      • N2 partial pressure in the atmosphere = 0.78 atm.
      • Solubility of nitrogen gas at 25°C and 1 atm = 6.8x10⁻⁴ mol/L.
      • Calculate concentration of nitrogen in water under atmospheric conditions = 5.3 × 10⁻⁴ mol/L

    Ways of Expressing Solution Concentration

    • Percent by Mass (%w/w): (mass of solute / mass of solution) x 100%
    • Percent by Volume (%v/v): (volume of solute / volume of solution) x 100%
    • Percent by Mass/Volume (%w/v): (mass of solute / volume of solution) x 100%
    • Parts per Million (ppm): (mass of solute / mass of solution) x 10⁶
    • Parts per Billion (ppb): (mass of solute / mass of solution) x 10⁹

    Other Concentration Units

    • Mole Fraction: Moles of a substance divided by total moles of solution. A mole fraction is the proportion of solute or solvent particles in the solution.
    • Molarity (M): Moles of solute per liter of solution (moles of solute/ lit of solution)
    • Molality (m): Moles of solute per kilogram of solvent (moles of solute/ kilogram of solvent)
    • Normality (N): Gram equivalent weight of solute per liter of solution.

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    Test your understanding of solubility concepts and experiments related to solid substances in liquids. This quiz covers factors influencing solubility, temperature effects, and specific experiments involving sodium chloride and sodium sulfate. Challenge yourself with questions that reinforce your knowledge of these key concepts.

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