5.3.3 Concentration of Solutions

• What does the concentration of a solution refer to?

  Amount of solute in solvent
• Molarity is defined as moles of solute per litre
• Molality is defined as moles of solute per kilogram of solvent.
• What is mole fraction equal to?

  Moles of solute / total moles
• The concentration of a solution can be expressed in different units
• Match the concentration unit with its definition:

  Molarity (M) ↔️ Moles of solute per litre of solution

  Molality (m) ↔️ Moles of solute per kilogram of solvent

  Mole Fraction (χ) ↔️ Moles of solute divided by total moles of solution

  Mass Percentage (%) ↔️ Mass of solute divided by total mass of solution, multiplied by 100
• Steps to calculate the molarity of a solution:

  1️⃣ Convert the volume from mL to L

  2️⃣ Use the molarity formula

  3️⃣ Substitute the values

  4️⃣ Calculate the molarity
• Molarity is calculated using the number of moles of solute per kilogram of solvent.

  False
• The concentration of a solution refers to the amount of solute
• Molarity is defined as moles of solute per litre of solution.
• Molality is defined as moles of solute per kilogram of solvent
• Mass percentage is calculated by dividing the mass of solute by the total mass of the solution and multiplying by 100.
• What determines the choice of concentration unit?

  Application and information available
• The formula for molarity is \( M = \frac{\text{moles of solute}}{\text{litres of solution
• Molality is calculated using the mass of the solvent in kilograms.
• What is the formula for mole fraction?

  $χ =$$\frac{\text{moles of solute}}{\text{moles of solute + moles of solvent}}$
• Mass percentage is always expressed as a fraction less than 1.

  False
• What is the unit of molarity?

  Moles per litre
• Mass concentration measures the mass of solute dissolved in a given volume
• To interconvert concentration units, you need to know the density of the solution and the molar mass of the solute and solvent.
• What is the formula to convert molarity to molality?

  $m =$$\frac{M}{\rho - M \times \text{Molar Mass}}$
• To convert molarity to molality, you need the density and the molar mass of the solute
• Steps to calculate the concentration of a solution using titration data:

  1️⃣ Perform the titration

  2️⃣ Record the volume of titrant used

  3️⃣ Calculate the moles of titrant

  4️⃣ Determine the moles of analyte

  5️⃣ Calculate the concentration of the analyte
• What is the formula to convert molarity to mole fraction?

  $χ =$ \frac{M}{\frac{1000\rho}{M_{\text{solvent}}} + M}
• Convert 2 M NaOH solution in water to mole fraction using water's molar mass 18 g/mol: 0.035
• What is the molar mass of water in g/mol?

  18
• Understanding concentration conversions allows for choosing the most appropriate unit for specific applications.
• Which concentration unit is most commonly used in titration experiments?

  Molarity
• In titration experiments, molarity (M) represents the number of moles of solute dissolved per litre
• What is the formula used to calculate concentrations in titration experiments?

  M_1 \times V_1 = M_2 \times V_2</latex>
• Match the variable in the titration formula with its meaning:

  $M_{1}$ ↔️ Molarity of the known solution

  $V_{1}$ ↔️ Volume of the known solution used

  $M_{2}$ ↔️ Molarity of the unknown solution

  $V_{2}$ ↔️ Volume of the unknown solution
• How is the molarity of an unknown solution ($M_{2}$) calculated using titration data?


  $M_{2} =$$\frac{M_{1} \times V_{1}}{V_{2}}$
• In an example titration, 25.0 mL of an unknown acid solution is titrated with 20.0 mL of 0.100 M NaOH.
• In the example titration, the calculated molarity of the unknown acid solution is 0.080
• What is the calculated molarity of the unknown acid solution in the example titration?

  0.080 M
• What is the most commonly used concentration unit in titration experiments?

  Molarity
• Molarity represents the number of moles of solute dissolved per litre of solution
• The formula $M_{1} \times V_{1} =$$M_{2} \times V_{2}$ is used to calculate concentrations in titration.
• What does $M_{1}$ represent in the titration formula?


  Molarity of known solution
• The formula to calculate the molarity of the unknown solution is M_{2} = \frac{M_{1} \times V_{1}}{V_{2}}</latex> where $V_{2}$ is the volume of the unknown solution