Chemistry: Solutions

Solution

• A solution consists of two major components: solute and solvent.
• A solution is a homogeneous mixture where the solute is absolutely soluble in the solvent.
• The definition of a solution is a homogeneous mixture of two or more than two components.

Solute and Solvent

• A solution has one solvent and one or more than one solute.
• Example: Lemonade (water as solvent and sugar and salt as solutes).

Classification of Solutions

• Based on the number of solutes and solvents, solutions can be classified into:
  • Binary solution (one solute and one solvent)
  • Ternary solution (one solvent and two solutes)
  • Quaternary solution (one solvent and three solutes)
• If not specified, a solution is assumed to be a binary solution.

Concentration of a Solution

• Concentration is a measure of the amount of solute in a solution.
• Expressions of concentration can vary, but they all convey the same information: how much solute is present in a given amount of solution.

Molarity (M)

• Molarity (M) is the number of moles of solute present in one liter of solution.
• Molarity is represented by the symbol M (capital M).
• Formula: M = moles of solute / volume of solution (in liters)
• Example: 3 M NaOH solution means 3 moles of NaOH are present in one liter of solution.

Molality (m)

• Molality (m) is the number of moles of solute present in one kilogram of solvent.
• Molality is represented by the symbol m (small m).
• Formula: m = moles of solute / mass of solvent (in kg)
• Example: 3 m NaOH solution means 3 moles of NaOH are present in one kilogram of solvent.

Mass by Volume Percentage

• Mass by volume percentage is the mass of solute present in 100 milliliters of solution.
• Formula: mass by volume percentage = (mass of solute in grams) / (volume of solution in milliliters) × 100
• Example: 10% mass by volume percentage NaOH solution means 10 grams of NaOH are present in 100 milliliters of solution.

Mass by Mass Percentage

• Mass by mass percentage is the mass of solute present per 100 grams of solution.
• Formula: mass by mass percentage = (mass of solute in grams) / (mass of solution in grams) × 100
• Example: 10% mass by mass percentage NaOH solution means 10 grams of NaOH are present in 100 grams of solution.### Calculating Mass of Solvent
• Mass of solution = mass of solute + mass of solvent
• Given 100 grams of solution and 10 grams of solute, mass of solvent = 100 - 10 = 90 grams
• Convert mass of solvent from grams to kilograms: 90 grams ÷ 1000 = 0.09 kg

Calculating Molality

• Molality = moles of solute ÷ mass of solvent in kilograms
• Calculate molality using the formula: moles of solute ÷ 0.09 kg

Calculating Molarity

• Molarity = moles of solute ÷ volume of solution in liters
• Calculate volume of solution using the density of the solution (if given)
• Convert volume from milliliters to liters

Volume by Volume Percentage

• Volume by volume percentage = volume of solute in milliliters ÷ volume of solution in milliliters × 100
• Formula: volume of solute ÷ volume of solution × 100
• Example: 10 volume by volume aqueous NaOH solution means 10 mL of solute is present in 100 mL of solution

Mole Fraction

• Mole fraction is represented by x (or χ)
• Mole fraction is a fraction, always between 0 and 1
• Formula for mole fraction of a component: moles of component ÷ total moles present in the solution
• Example: mole fraction of A = moles of A ÷ (moles of A + moles of B)
• The sum of mole fractions of all components is always equal to 1
• If mole fractions of two components are known, the third component's mole fraction can be calculated by subtracting them from 1

Parts Per Million (PPM)

• Parts per million is similar to percentage, but with a different scale
• Formula: mass of solute in grams ÷ mass of solution in grams × 10^6
• PPM is used to calculate the number of grams of solute per 10^6 grams of solution
• Example: 3 ppm of Cl2 means 3 grams of solute is present in 10^6 grams of solution### Concentration Terms and Vapor Pressure
• The concept of concentration terms is crucial in understanding vapor pressure.
• Vapor pressure is the maximum pressure exerted by a vapor in equilibrium with a liquid.
• At a saturated condition, the pressure exerted by vapor molecules is equal to the vapor pressure.

Vapor Pressure and Boiling Point

• Imagine a closed container with water inside, where water molecules (particles) are in constant motion.
• Particles on the surface of the liquid have a higher energy and are unbalanced, wanting to escape the surface.
• When a particle on the surface gains enough energy, it escapes the surface, creating a vapor and exerting pressure on the container walls.
• At a particular temperature, an equilibrium is reached, where equal numbers of molecules are converted into the vapor phase and the liquid phase.
• This equilibrium point is known as the saturated vapor or saturation point.
• The pressure exerted at this point is the vapor pressure.

Characteristics of Vapor Pressure

• Vapor pressure is constant at a particular temperature.
• It depends only on the temperature and nature of the liquid.
• Vapor pressure does not depend on the volume of the container or the amount of the liquid.

Raoult's Law

• Raoult's law states that the partial pressure of any component in a solution is proportional to the mole fraction of that component in the liquid solution.
• The partial pressure of a component is directly proportional to its mole fraction.
• If the mole fraction of a component is more, it will exert more pressure.
• Raoult's law is used to calculate the vapor pressure of a mixture of two volatile components.

Dalton's Law

• Dalton's law states that the partial pressure of a component in the vapor phase is equal to the mole fraction of that component in the vapor phase multiplied by the total pressure.
• Dalton's law is used to derive expressions for the partial pressure of a component in the vapor phase.

Vapor Pressure of a Mixture of Two Volatile Components

• The total pressure of a mixture of two volatile components is equal to the sum of the partial pressures of the two components.
• The partial pressure of each component can be calculated using Raoult's law.
• The total pressure can be calculated using the expression: p_total = p_a + p_b.

Raoult's Law and Non-Volatile Solutes

• If one of the components in a solution is non-volatile, it means that it does not have any vapor pressure.
• The vapor pressure of a solution with a non-volatile solute is only due to the volatile solvent.
• The partial pressure of the volatile solvent is directly proportional to its mole fraction in the solution.

Solution

• A solution is a homogeneous mixture where the solute is absolutely soluble in the solvent.
• It consists of two major components: solute and solvent.

Solute and Solvent

• A solution has one solvent and one or more than one solute.
• Example: Lemonade (water as solvent and sugar and salt as solutes).

Classification of Solutions

• Solutions can be classified based on the number of solutes and solvents.
• Types of solutions: binary solution (one solute and one solvent), ternary solution (one solvent and two solutes), and quaternary solution (one solvent and three solutes).

Concentration of a Solution

• Concentration is a measure of the amount of solute in a solution.
• Expressions of concentration convey the same information: how much solute is present in a given amount of solution.

Molarity (M)

• Molarity (M) is the number of moles of solute present in one liter of solution.
• Formula: M = moles of solute / volume of solution (in liters).
• Example: 3 M NaOH solution means 3 moles of NaOH are present in one liter of solution.

Molality (m)

• Molality (m) is the number of moles of solute present in one kilogram of solvent.
• Formula: m = moles of solute / mass of solvent (in kg).
• Example: 3 m NaOH solution means 3 moles of NaOH are present in one kilogram of solvent.

Mass by Volume Percentage

• Mass by volume percentage is the mass of solute present in 100 milliliters of solution.
• Formula: mass by volume percentage = (mass of solute in grams) / (volume of solution in milliliters) × 100.
• Example: 10% mass by volume percentage NaOH solution means 10 grams of NaOH are present in 100 milliliters of solution.

Mass by Mass Percentage

• Mass by mass percentage is the mass of solute present per 100 grams of solution.
• Formula: mass by mass percentage = (mass of solute in grams) / (mass of solution in grams) × 100.
• Example: 10% mass by mass percentage NaOH solution means 10 grams of NaOH are present in 100 grams of solution.

Calculating Mass of Solvent

• Mass of solution = mass of solute + mass of solvent.
• Given 100 grams of solution and 10 grams of solute, mass of solvent = 100 - 10 = 90 grams.

Calculating Molality

• Molality = moles of solute ÷ mass of solvent in kilograms.
• Calculate molality using the formula: moles of solute ÷ 0.09 kg.

Calculating Molarity

• Molarity = moles of solute ÷ volume of solution in liters.
• Calculate volume of solution using the density of the solution (if given).
• Convert volume from milliliters to liters.

Volume by Volume Percentage

• Volume by volume percentage = volume of solute in milliliters ÷ volume of solution in milliliters × 100.
• Formula: volume of solute ÷ volume of solution × 100.
• Example: 10 volume by volume aqueous NaOH solution means 10 mL of solute is present in 100 mL of solution.

Mole Fraction

• Mole fraction is represented by x (or χ).
• Mole fraction is a fraction, always between 0 and 1.
• Formula for mole fraction of a component: moles of component ÷ total moles present in the solution.
• Example: mole fraction of A = moles of A ÷ (moles of A + moles of B).

Parts Per Million (PPM)

• Parts per million is similar to percentage, but with a different scale.
• Formula: mass of solute in grams ÷ mass of solution in grams × 10^6.
• PPM is used to calculate the number of grams of solute per 10^6 grams of solution.
• Example: 3 ppm of Cl2 means 3 grams of solute is present in 10^6 grams of solution.