Chemistry Solutions Key Concepts

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What is the primary condition for forming an ideal solution?

  • The solution must be at high pressure.
  • The solution must be saturated.
  • The solution must obey Raoult's law. (correct)
  • The solution must have a high viscosity.

Why do chlorobenzene and bromobenzene form an ideal solution?

  • They mix in equal volumes.
  • They are both polar solvents.
  • They have different boiling points.
  • They exhibit equal interactions between molecules. (correct)

How is the concentration of a solute in trace amounts expressed?

  • In grams per liter.
  • In percentage by volume.
  • In parts per million. (correct)
  • In parts per billion.

Which gas has greater solubility in water, N2 or O2?

<p>O2 because it has a lower K H value. (A)</p> Signup and view all the answers

Under what condition are molality and molarity identical?

<p>In dilute solutions. (C)</p> Signup and view all the answers

What effect does adding HgI2 to KI solution have on vapor pressure?

<p>It increases the vapor pressure. (B)</p> Signup and view all the answers

What happens to the boiling point when two miscible liquids showing negative deviation are mixed?

<p>It increases. (B)</p> Signup and view all the answers

Which liquid has a higher boiling point if liquid Y has a higher vapor pressure than liquid X?

<p>Liquid X will have a higher boiling point. (B)</p> Signup and view all the answers

What type of solution is formed when mercury is mixed with sodium?

<p>Liquid in solid solution (A)</p> Signup and view all the answers

Which solid solution results from mixing components with significantly different molecular sizes?

<p>Interstitial solid solution (A)</p> Signup and view all the answers

What does a semimolar solution represent in terms of molarity?

<p>0.5 M (B)</p> Signup and view all the answers

If a solution contains equal moles of water and C2H5OH, what is the mole fraction of water?

<p>0.5 (A)</p> Signup and view all the answers

Which of the following is dimensionless?

<p>Mole fraction (C)</p> Signup and view all the answers

How is the percentage concentration of a solution calculated?

<p>Component mass divided by total solution mass times 100 (C)</p> Signup and view all the answers

Why do gases become less soluble in liquids when temperature rises?

<p>High velocities reducing interaction (C)</p> Signup and view all the answers

What is the molarity of a decimolar solution?

<p>0.1 M (A)</p> Signup and view all the answers

What is the main reason for a solution of a non-volatile and non-electrolyte solute boiling at a higher temperature?

<p>It lowers the vapor pressure of the solution. (B)</p> Signup and view all the answers

What is the calculated Van’t Hoff factor for the association of solute A in benzene?

<p>0.467 (B)</p> Signup and view all the answers

What does the equation $ riangle T_b = K_b m$ signify in relation to boiling point elevation?

<p>It connects molality of the solute with the elevation in boiling point. (C)</p> Signup and view all the answers

Why is calcium chloride (CaCl2) effective for clearing snow from roads?

<p>It prevents the formation of ice by lowering the freezing point. (A)</p> Signup and view all the answers

If the depression in freezing point ($, , , , , , , , , , , \Delta T_f$) is given by the formula $, , , , , , , , , iK_f m$, what value was used for molality (m) in the freezing point depression calculation?

<p>0.250 m (C)</p> Signup and view all the answers

What freezing point is reached after considering the depression caused by adding the solute to benzene?

<p>4.90°C (A)</p> Signup and view all the answers

What phenomenon causes abnormal molecular weights in colligative properties?

<p>The association or dissociation of solute molecules. (C)</p> Signup and view all the answers

Given the isotonic solutions, what is the molecular mass of urea calculated from a 5% sucrose solution?

<p>59.9 g/mol (B)</p> Signup and view all the answers

What does the Van’t Hoff factor account for in colligative properties?

<p>The number of particles the solute dissociates into. (B)</p> Signup and view all the answers

What is the osmotic pressure of a 0.0103 molar solution if the Van’t Hoff factor is calculated to be approximately 2.95?

<p>0.75 atm (C)</p> Signup and view all the answers

Why does ethylene glycol lower the freezing point of water in vehicle radiators?

<p>It prevents water from freezing during cold temperatures. (D)</p> Signup and view all the answers

How does the freezing point depression of 0.01 m sodium chloride compare to that of 0.01 m glucose solution?

<p>It is nearly twice that of glucose solution. (C)</p> Signup and view all the answers

What is the ppm equivalent of the maximum allowable level of nitrates in drinking water set at 45 mg nitrate ions/dm³?

<p>45 ppm (B)</p> Signup and view all the answers

What effect does high pressure have on the solubility of gases in liquids?

<p>It increases solubility. (B)</p> Signup and view all the answers

In a solution where phenol (C6H5OH) causes a depression in freezing point of 7K, what information does this imply about phenol's behavior in the solvent?

<p>Phenol dimerizes in solution (B)</p> Signup and view all the answers

What value is assumed for Kf used for calculating the freezing point depression of phenol in the solution?

<p>14 Km⁻¹ (C)</p> Signup and view all the answers

What is the degree of association of C6H5COOH if it forms a dimer in solution?

<p>99.2% (B)</p> Signup and view all the answers

What is the corrected molar mass of C6H5COOH calculated from its freezing point depression?

<p>241.98 g/mol (D)</p> Signup and view all the answers

How many moles of NaCl are needed to achieve a freezing point depression of 3K in 1kg of water?

<p>0.81 moles (B)</p> Signup and view all the answers

What is the Van’t Hoff factor (i) for calcium nitrate, Ca(NO3)2, based on a degree of dissociation of 70%?

<p>2.4 (D)</p> Signup and view all the answers

If three molecules of a solute (A) associate to form species A3 in solution, what is the degree of association given as 0.8?

<p>0.8 (C)</p> Signup and view all the answers

What is the calculated vapor pressure of a solution if the vapor pressure of the pure solvent is 760 mm Hg?

<p>746.1 mm Hg (C)</p> Signup and view all the answers

Calculate the moles of Ca(NO3)2 present in 7g with a molar mass of 164 g/mol.

<p>0.0426 moles (C)</p> Signup and view all the answers

What is the freezing point of benzene given its freezing point depression constant (Kf) is 5.13 K/m and the concentration of the solute is 0.25 molal?

<p>-5.5 °C (C)</p> Signup and view all the answers

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Study Notes

Solutions - Key Concepts

  • Types of Solutions:
    • Liquid in solid: A solid solvent with a liquid solute, e.g., mercury in sodium (amalgam).
    • Interstitial solid solution: Occurs when two solids with significantly different molecule sizes mix.
  • Concentration Terms:
    • Semimolar: A solution with a molarity of M/2.
    • Decimolar: A solution with a molarity of M/10.
    • Mole Fraction: A dimensionless quantity representing the ratio of a component's moles to the total moles in the solution, e.g., 0.5 mole fraction of water in a solution with equal moles of water and ethanol.
  • Solubility Trends:
    • Gases in liquids: Solubility decreases as temperature increases due to increased gas kinetic energy and shifting of equilibrium towards the gaseous state.
  • Ideal Solutions:
    • Conditions: Follow Raoult's law, homogenous mixtures, no volumetric or thermal effects.
    • Example: Mixture of chlorobenzene and bromobenzene due to equal interaction between molecules.
    • Non-ideal Examples: Mixture of chloroform and acetone.
  • Concentration of Trace Amounts:
    • Parts per million (ppm): Used for expressing the concentration of solutes present in trace amounts.
  • Henry's Law:
    • KH (Henry's constant): Lower KH value signifies higher solubility of gas in a liquid.
    • Solubility: O2 has a lower KH value than N2, therefore it is more soluble in water at the same partial pressure.
  • Molarity vs. Molality:
    • Equivalence: In extremely dilute solutions, molarity and molality are nearly identical.
  • Colligative Properties:
    • Vapor Pressure: Elevation in vapor pressure occurs when a solute like HgI2 forms a complex with KI, decreasing the number of solute particles.
    • Boiling Point: Solutions showing negative deviation from Raoult's law have a lower vapor pressure and therefore a higher boiling point.
    • Freezing Point: CaCl2 is used to de-ice roads as it depresses the freezing point of water, preventing ice formation.
    • Antifreeze: Ethylene glycol, used in car radiators, lowers the freezing point of water, preventing damage in cold climates.
    • Abnormal Molecular Weights: Colligative properties can give abnormal molecular weights due to association or dissociation of solute molecules, as explained by the van't Hoff factor.
    • Freezing Point Depression: The depression in freezing point for 0.01m NaCl is nearly double that of 0.01m glucose because NaCl dissociates into two ions while glucose doesn't.
  • Van't Hoff Factor (i):
    • Association: i is less than 1 (e.g., dimerization of carboxylic acids)
    • Dissociation: i is greater than 1 (e.g., electrolytes like NaCl)
  • Osmotic Pressure:
    • Isotonic Solutions: Solutions with equal osmotic pressure have equal concentrations.
    • Molecular Mass of Urea: Calculating the molecular mass of urea in an isotonic solution with sucrose.
  • Calculation of Molality, Freezing Point, and Percentage Association:
    • Comprehensive explanation and examples of how to calculate molality, freezing point, and the percentage of association for solutions.
  • Maximum Allowable Level of Nitrates in Drinking Water:
    • The maximum allowable level of nitrate ions is 45 mg/L, equivalent to 45 ppm.

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