Unit 3 math practice

FRQ Question 1: Molecular Polarity

a. Define molecular polarity and describe how the molecular geometry and dipole moments of bonds contribute to the overall polarity of a molecule.

b. Using carbon tetrafluoride (CF4) and nitrogen trifluoride (NF3) as examples, calculate the dipole moment for each bond using the formula ( \mu = q \times r ), where ( q ) is the charge difference (in Coulombs) and ( r ) is the bond length (in meters). Describe how the total dipole moment affects the overall polarity of the molecule.

FRQ Question 2: Intermolecular Forces

a. Compare the strength of intermolecular forces in the following compounds: Water (H₂O), Sodium Chloride (NaCl), and Iron (Fe). Provide calculations to determine the energies involved in breaking these forces (use bond energies, e.g., for H₂O, bond energy is approximately 463 kJ/mol).

b. For a substance with dipole-dipole interactions, if the enthalpy of vaporization is found to be 40 kJ/mol, use this value to calculate the predicted boiling point change when transitioning from liquid to gas, assuming constant pressure.

FRQ Question 3: Kinetic Molecular Theory

a. Explain the basic assumptions of the kinetic molecular theory (KMT).b. For an ideal gas, if the temperature is 298 K and the pressure is 1 atm, calculate the average kinetic energy of a gas molecule using the formula ( KE = \frac{3}{2}kT ), where ( k ) is Boltzmann's constant ( (1.38 \times 10^{-23} J/K) ). Show your calculations.

FRQ Question 4: Solutions and Separation Techniques

a. Define the principle "like dissolves like" with examples, and discuss the solubility of a solute in a given solvent. If the mass of salt (NaCl) is 5 grams in 100 mL of water, calculate the molarity (M) of the solution using the formula ( M = \frac{moles \ of \ solute}{liters \ of \ solution} ).

b. In paper chromatography, the distance traveled by a component is measured. If the solvent front travels 10 cm and a dye moves 7 cm, calculate the retention factor (Rf) using the formula ( Rf = \frac{distance \ traveled \ by \ solute}{distance \ traveled \ by \ solvent} ). Calculate and interpret the Rf value in terms of polarity.