Chemistry Solutions Key Concepts

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Questions and Answers

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?

O2 because it has a lower K H value. Signup and view all the answers

Under what condition are molality and molarity identical?

In dilute solutions. Signup and view all the answers

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

It increases the vapor pressure. Signup and view all the answers

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

It increases. Signup and view all the answers

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

Liquid X will have a higher boiling point. Signup and view all the answers

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

Liquid in solid solution Signup and view all the answers

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

Interstitial solid solution Signup and view all the answers

What does a semimolar solution represent in terms of molarity?

0.5 M Signup and view all the answers

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

0.5 Signup and view all the answers

Which of the following is dimensionless?

Mole fraction Signup and view all the answers

How is the percentage concentration of a solution calculated?

Component mass divided by total solution mass times 100 Signup and view all the answers

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

High velocities reducing interaction Signup and view all the answers

What is the molarity of a decimolar solution?

0.1 M 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?

It lowers the vapor pressure of the solution. Signup and view all the answers

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

0.467 Signup and view all the answers

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

It connects molality of the solute with the elevation in boiling point. Signup and view all the answers

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

It prevents the formation of ice by lowering the freezing point. 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?

0.250 m Signup and view all the answers

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

4.90°C Signup and view all the answers

What phenomenon causes abnormal molecular weights in colligative properties?

The association or dissociation of solute molecules. Signup and view all the answers

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

59.9 g/mol Signup and view all the answers

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

The number of particles the solute dissociates into. 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?

0.75 atm Signup and view all the answers

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

It prevents water from freezing during cold temperatures. 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?

It is nearly twice that of glucose solution. 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?

45 ppm Signup and view all the answers

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

It increases solubility. 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?

Phenol dimerizes in solution Signup and view all the answers

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

14 Km⁻¹ Signup and view all the answers

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

99.2% Signup and view all the answers

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

241.98 g/mol 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?

0.81 moles 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%?

2.4 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?

0.8 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?

746.1 mm Hg Signup and view all the answers

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

0.0426 moles 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?

-5.5 °C Signup and view all the answers

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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Test your knowledge on key concepts related to solutions in chemistry. This quiz covers types of solutions, concentration terms, solubility trends, and the characteristics of ideal solutions. Perfect for students looking to reinforce their understanding of solution chemistry.