CH102 Quiz 1 Main Topics and Formulas

Describe the intermolecular forces:

Dispersion: Electrons polarize the atom by moving to one side; sole force present in nonpolar molecules; closer together = stronger IMF and higher boiling point

Dipole-Dipole: Polar molecules create partial charges due to unequal sharing of electrons; more polar = stronger IMF and higher boiling point

Hydrogen Bonding: Extra-strength dipole-dipole interactions involving H bonded to N, O, F

Ion-Dipole: Ionic compounds (metal + nonmetal) have highest boiling point

What happens to temperature during the phase change diagram?

Heat is constantly added; temperature only increases within a phase but is constant during phase changes

What is enthalpy?

Heat required

Formula for phase change:

ΔH = ΔH (transition) x moles

Formula for within phase:

ΔH = total mass x specific heat x ΔT

How is a solution formed?

A solute dissolves in a solvent to form a solution

Describe saturated vs unsaturated solutions:

Saturated: The maximum amount of solute has dissolved in the solvent

Unsaturated: More solute could still dissolve in the solvent

Describe polar/nonpolar solutions:

Polar solutes dissolve in polar solvents; nonpolar solutes dissolve in nonpolar solvents

How can you tell if something is polar or nonpolar?

Nonpolar: Mostly C and H; 5 or more C with only 1 or 2 N or O

Polar: Water; less than 5 C with only 1 or 2 N or O; equal amounts of C and O, H-bonds

Describe miscible vs immiscible liquids:

Miscible: mix together

Immiscible: do not mix; form layers

What happens in increased temperature?

Gas: Increased pressure or temperature = decreased solubility

Solid: Increased temperature = increased solubility

Molarity (M)

Moles of solvent / L of solution

Molality (m)

Moles of solvent / kg of solvent

Mole Fraction (X)

Moles of component / total moles

Mass Percent

(Mass of solvent / mass of solution) x 100

What is a freezing point depression?

A decrease in freezing point due to the addition of solute to solvent;

Lowest freezing point/highest boiling point = highest concentration of particles

Freezing Point Depression Formula:

ΔTf = i K fm where i = number of solute particles

Tf = Tf (solvent) - ΔTf